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Vital Principle
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Chapters 30
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IT may be assumed that all knowledge is beautiful and estimable; but as one branch may be more so than another, either because of the exactness which is requisite for its examination, or from its treating of objects more exalted and wonderful than any others, so, on both these accounts, we may reasonably assign the first place to an inquiry into Vital Principle. For the knowledge of it promises to contribute largely to all truth, and most especially to truth in relation to nature, since it is the origin, as it were, of living beings. The object of our inquiry, then, is to study and ascertain its nature and its essence, as well as its accidents, of which some seem to be its own peculiar affections, and some to belong to living beings, as original properties, through it.

Let us premise, however, that the attempt to attain to any certainty with respect to it is beset with almost insuperable difficulties; for as this has much in  common with many other inquiries, with every inquiry, I mean, instituted for ascertaining the essence and the thing itself, it might hastily be supposed that, as demonstration is the method for studying particular bodies in their accidents, there may be some one special method of investigation when our object is to learn what is the essence of a thing, and that that method ought to be sought for on this occasion. If, however, there is no one common method for ascertaining what any thing in itself is, the systematic treatment of our subject is rendered still more difficult; for, in that case, it will be necessary to adopt, for each particular subject, some one particular method. Although it may be manifest, besides, that the inquiry should be by some kind of demonstration, or division, or other method, there will still remain many difficulties and many liabilities to error in fixing upon the principles from which the inquiry should set out; for the principles of different subjects differ, as those of number are not those of plane surfaces.

It may be well, perhaps, before proceeding further, to distinguish the “genus” to which Vital Principle belongs, and determine what it is—determine, I mean, whether it is a something and essence, or quantity, or quality, or any other of the classified categories; as also, a distinction of no small importance, whether it is among entities in potentiality, or whether rather it is a reality. We have to consider too whether  Vital Principle is divisible or without parts, and whether every Vital Principle is or is not the same in kind, and, if not the same, whether the difference is generic or specific; but they who now are engaged in discussing and exploring Vital Principle seem to give exclusive attention to that of man. We must be on our guard against this, however, so that it may not escape us whether there is but one definition for Vital Principle as for animal, or whether it must be different for each creature, as for a horse, a dog, or a man. The term animal, besides, taken in an universal sense, is either without meaning, or of very secondary value; and so equally is every other common term which might be predicated of this subject. If, on the other hand, there are not several Vital Principles, but parts only of a single Principle, we have to settle whether we should commence the inquiry with the Principle as a whole, or, contrariwise, with its parts; and, with respect to the parts, it is difficult to determine which of them have been constituted differently from others; it is difficult also to say whether we should study the parts before their functions, as the mind before thought, or sensibility before sensation; and so for other faculties and functions. If it be expedient to commence the inquiry with functions, it may be a question whether it would not be better here also to study first their opposites; as the object of perception before that which perceives, and thought  before that which thinks. Now, the knowledge of any thing in itself seems to be useful towards a right conception of the causes of the accidents in substances; as, in mathematics, the knowledge of straight and curve, line and surface, is requisite for perceiving to how many right angles the angles of the triangle are equal. But the knowledge of the accidents contributes, largely, in its turn, towards knowing what the thing, essentially, is; for whenever we may be able, from the appearance of any substance, to recount the whole or the greater number of its accidents, we are then best prepared to say what its essence is. Thus, the essence is the proper beginning for every demonstration, so that all the definitions, which do not make known, or make it easy to conjecture what may be the accidents of any substance, are to be regarded as dialectic and unprofitable subtleties.

It is difficult to determine whether all the emotions of Vital Principle are common to it and its recipient, or whether some one emotion belongs to it exclusively; and this is a question, which, although not easily settled, it is necessary to entertain. There is scarcely one of the many emotions which are derived from the Vital Principle, (as anger, or courage, desire, or feeling,) in the manifestation of which the Vital Principle can be said to be affected, actively or passively, without the body; the faculty of thought seems to be the peculiar property of the Vital Principle  but whether thought be imagination of some kind, or never unaccompanied by imagination, still we must admit that it cannot be exercised without the body. If, then, there is any one function or emotion which is peculiar to the Vital Principle, we should admit that it might be isolated from the body; but, if no one belongs to it, exclusively, then we say that it cannot be separate from one. But, just as many accidents concur in the quality straightness, in so far as straightness (as, for instance, among others, to touch a brazen sphere at a point, which, were it apart from some kind of body, it could not do), so straightness is inseparable from a body, since it is ever found together with one. In the same way all the emotions of the Vital Principle (such as courage, gentleness, fear, pity, daring, joy, love and hatred,) seem to be manifested together with the body; for the body is affected, simultaneously, by them. As evidence of which, there are times when we are neither excited nor alarmed, although misfortunes may be trying and palpable, while, at other times, when the body is plethoric, or in a state akin to that of anger, we are moved by incidents which are trivial and unimportant. And what makes this yet more apparent is, that, at times, without the occurrence of aught to occasion alarm, we are thrown into the state of persons under terror; and if this be true, it is clear that all such emotions are material conditions. So  that the definition of any one of them, as that of anger for example, may be said to be the motion of a body of particular nature, or part or function of a body, by such a cause, and for such an end.

Thus, for these reasons, it is for the physiologist to study the Vital Principle, either as a whole, or under some particular manifestation. But the physiologist and the metaphysician would differ widely in their definition of any one of those emotions, as that of anger, for example; which, while the latter would hold to be desire for retaliation, or some such motive, the former would maintain to be ebullition of blood, or excess of heat about the heart. The one of these, in fact, accounts for the passion by the matter, and the other by the form and cause; for the form is the cause of the thing, which, if it is to be, must, of necessity, be in a special matter. Thus, the cause of a house, for instance, is such as this—"to be a shelter to avert injury from rain, wind, and heat;" and here the physiologist will speak of stones, bricks, and rafters, while the metaphysician will, in these materials, only behold the form to be adopted for those purposes. Which, then, of these is the physiologist? Is it he who studies only the matter without reference to the cause, or he who is occupied with the cause only? Or is it rather he who judges both from cause and matter; and which of the two is he? May we not however rather say that there is one who is  engaged upon the properties which are inseparable and only in so far as they are inseparable from matter, while to the physiologist it belongs to judge of such emotions and functions as emanate from particular bodies and peculiar matter? Properties different from these belong to another; and some of them to an artisan, a physician or builder, as the case may be, while the mathematician has to do with properties which are not inseparable from matter, but which, as they do not belong to any particular body, admit of being treated as abstractions; and abstract qualities, as abstractions, belong to the transcendental philosopher.

Let us, however, return to the point where our discussion broke off, and repeat that the emotions of Vital Principle, such as anger and fear, for instance, in so far as they are innate, are inseparable from the material frame-work of animals; and that they are not to be regarded as a line or a surface.


AS we are now entering upon the study of Vital Principle, and are encompassed with doubts which ought to be resolved, it will be incumbent upon us to gather the opinions of such of the earlier writers as have suggested any thing concerning it, in order that we may be able as well to adopt their happier conceptions as to be on our guard against their errors.  The suitable opening for this inquiry into the Vital Principle is to lay down the properties which appear, most especially, to belong to it. The animated being, then, seems to be especially distinguished from whatever is inanimate by the two properties of motion and feeling; and these two are almost the only distinctions which have been transmitted to us by the earlier writers upon the subject. Thus, some of them maintain that the Vital Principle is in the largest, fullest sense a motor power; and as they believed that nothing can impart motion unless it be self-motive, they assumed that the Vital Principle must be among beings which are self-moved. Hence Democritus says that it is a kind of fire and heat, and as forms and atoms are, according to him, infinite, he speaks of those which are spherical and apparent in the sun's beams, while passing through chinks in doors, as fire and Vital Principle; and further says, that those atoms, collectively, are the elements of universal nature. Leucippus, in like manner, is disposed to regard the spherical atoms as Vital Principle, both on account of those forms being best adapted for penetrating every where, and best able, from being self-motive, to give motion to other things; and thus they both assume that it is Vital Principle which imparts motion to living beings. Hence, too, they make breathing to be the boundary of life—for they maintain that the envelopment of animal bodies  crushes by its contraction those forms of atoms which, from never being at rest, give motion, and that compensation is afforded for their exit by the entrance of other like forms, during inspiration; and that these forms, while entering, resist the contracting and solidifying power, and preclude the expulsion of all the atoms which are essential to life. They further maintain that animals can live only so long as they can support this process. The opinion adopted by the Pythagoreans seems to be to the same purport—for some of them have maintained that Vital Principle is the motes in the air, and others that it is that which gives motion to the motes; and it has thus been said of those corpuscles, because of their appearing to be constantly moving, although the air may be quite still.

To the same point do they also come who say that the Vital Principle is self-motive ; for all these philosophers seem to have assumed that motion is the most characteristic property of the Vital Principle ; and that, while all other things are moved by it, it is self-moved, and the more so, as they do not see any motor which is not self-moved.

Anaxagoras, in like manner, says that the Vital Principle is a motive force, and the same opinion may be attributed to any one who, with him, may have maintained that the mind has given motion to the universe; and yet his opinion is not altogether in  accordance with that of Democritus. Democritus, in fact, maintains that Vital Principleand mind are absolutely identical ; that the apparent is the true; and that Homer, therefore, has done well in representing Hector as "changing his mind while he lay." Thus he does not employ the term mind as a faculty for the attainment of truth, but makes mind to be identical with the Vital Principle. Anaxagoras is less explicit upon these points ; for, in many places, he speaks of mind as the source of the beautiful and the true, while, elsewhere, he says that it is identical with the Vital Principle, and innate in all creatures, larger or smaller, higher or lower, in the scale of being ; but it is manifest that mind, in the sense of intellect, is not equally allotted to all animals, nor even to all men.

Thus they who have looked upon living beings with respect to motion, have assumed that the Vital Principle is the most motive of entities, and so many as have looked upon them with respect to knowledge and sentient perception, have said that the Vital Principle comprises all first causes; of which, while some admit of several, others maintain that there is only this one. Empedocles, for instance, seems to maintain that the Vital Principle is derived from all the elements, and that each element is Vital Principle, as he says that " by earth we perceive earth, by water water, by air air, by fire destructive  fire, by attraction attraction, and by repulsion dire repulsion."

Plato, in a like manner, in the Timaeus, derives the Vital Principle from the elements—for like, therein, is known by like, and things are derived from first causes; and so, likewise, have things been denned by him in the treatises "upon philosophy." According to them, animal, in itself, is derived from the abstract idea of unity, and primal length, and breadth, and depth; and other things in a somewhat similar manner. It is besides maintained, but in a different sense, that the mind is unity, and knowledge duality, although, as one branch, it is unity; and that the number of the surface is opinion, that of the solid sensation, for numbers were spoken of by him as forms and first causes, and as derivatives from the elements. Thus, some things are discriminated by mind, some by knowledge, some by opinion, and others by sensation; as the numbers which represent those faculties are the forms of things.

Since the Vital Principle has to some appeared to be both motive and capable of knowing, there are writers who have combined motion and intelligence, and then represented the Vital Principle as a number endowed with self-motion.

Philosophers differ with respect to first causes, both as to their nature and number; but they who make them corporeal differ most from those who hold  them to be incorporeal; and from these again they differ who make them to be a combination both of corporeal and incorporeal molecules. They differ also with respect to the number of such causes, as some adopt only one while others admit of several; and, in accordance with these conclusions, they form their estimate of the Vital Principle ; but yet they have all assumed, and not unreasonably, that it is of the nature of first causes to be motive. Hence, the Vital Principle has to some appeared to be fire, as fire, besides being the most attenuated and most incorporeal of the elements, is both self-motive and a primal cause of motion in other things.

Democritus has expressed himself more clearly than any other writer in specifying the causes of each of those properties: for he says that the Vital Principle is identical with the mind, and to be placed among primal and indivisible bodies; that it is motive, owing to the tenuity of its parts and its form; that of forms the spherical is the most mobile, and that this is the form both of mind and fire.

Anaxagoras seems, as we have already said, to distinguish the mind from the Vital Principle, although he employs both terms as if synonymous; excepting that he sets down the mind as being, in the fullest sense, the origin of all things. Thus he says that the mind alone of all entities is homogeneous, unmixed, and pure; and to the same principle he attributes  the properties both of knowing and imparting motion, as he maintains that it is the mind which has given motion to the universe.

Thales, too, from what has been recorded of him, seems to have assumed that the Vital Principle is something motive, since he said that the loadstone must have a Vital Principle because it gives motion to iron.

Diogenes, together with some other writers, held the Vital Principle to be air, because air was believed to be the most attenuated of the elements, as well as an originating cause; and that, through these properties, the vital principle is able both to recognise things and to impart motion to them. They argued that Vital Principle, as being a first cause and the origin of other things, is able to recognise them; and that, as being the most attenuated of entities, it is motive.

Heraclitus also maintains that the Vital Principle is a first cause, since, in his system, it is the exhalation out of which he constitutes every thing else ; he regards it too as the most incorporeal of entities, and as being "in a constant state of flux;" and further says, that the moved must be known to the motor. He agreed, in fact, with most others in believing all things to be in motion.

The opinions of Alcmaeon upon the Vital Principle seem to be very like those just cited—for he says that it is immortal, on account of its resemblance to the  immortals, and that this resemblance is manifested by its being continuously in motion; for all divine bodies, he argues, the moon, sun, stars, and heavens, are continuously moving.

Some writers of smaller pretension—and Hippo was one of them—have ventured to represent the Vital Principle as water; and they seem to have been led to this persuasion by the nature of semen, which, in all creatures, is fluid. Hippo, indeed, reproves those who assert that the Vital Principle is blood, because blood is not semen; and semen is, according to him, the first principle of life.

Others have maintained, as did Critias, that the Vital Principle is blood, from their assuming that the most peculiar property of blood is feeling, and that feeling is imparted to us through the nature of blood. All the elements, in fact, have had their partisans, excepting earth; and no one has adopted it, unless such an opinion may be attributed to those who have derived the Vital Principle from all, or made it to be all the elements.

Thus, all these philosophers define Vital Principle by the three properties, motion, feeling, and incorporeity, each of which is referrible to first causes. Such of them, therefore, as define it by the faculty of knowing, make it to be an element or a derivative from the elements, and, with one exception, their opinions coincide;—for they all maintain that like is  known to like, and, since the Vital Principle recognises all things, they constitute it out of all first causes. But such as admit of only one cause and one element, set down Vital Principle as being that one, be it fire or air ; and such as admit of several first causes, set down Vital Principle as being multiple also. Anaxagoras stands alone in maintaining that mind is impassive and without anything in common with aught else ; but, even were it so, he has not explained, nor is it easy from what he has said to explain, how or for what purpose it is to recognise anything. So many writers as admit contraries among first causes, constitute the Vital Principle out of contraries, and so many as admit only one contrary, whether hot or cold, or other analogous contrast, make the Vital Principle to be that one. Hence, led by the terms, some maintain that Vital Principle is heat, because from heat the term life has been adopted; and others affirm that it is cold, because from cold, through respiration, the term Vital Principle has been derived.

Such, then, the opinions which have been transmitted to us upon Vital Principle, and such the reasons upon which those opinions have been grounded.


Before proceeding further, let us consider the nature of motion; for it may not only be untrue that Vital Principle is, as some affirm, essentially self-motive or capable of producing motion; but it may be one of those entities to which motion cannot possibly belong; and it has already been said that the motor is not necessarily itself in motion.

Everything moved admits of being moved in two ways: either by itself or by something else; and by something else we mean whatever is moved from being in something which is moving, as sailors for instance,—for they are not moved as is the vessel, since it is moved by itself, but they are moved from being in that which is moved. This is clear by reference to their limbs—a particular movement of the feet is walking, and walking is man's progression; but the sailors do not at that time move by walking. Since then motion may be spoken of in this two-fold

sense, let us consider whether the Vital Principle moves by itself, and whether it partakes also of motion communicated to it. As there are four kinds of movement, translation, change, growth, decay, it follows that the Vital Principle should move according to one, or more than one, or all of them; and if it do not move by chance, then motion must be natural to it; and if so, then locality, for all the movements above alluded to are local.

But if Vital Principle be essentially self-motive, then accidental movement will not belong to it as to a white colour or a length of three cubits; for these properties do move, but then it is by accident, and owing to the bodies to which they belong happening to be in motion. Thus, there cannot be for them any locality as there will be for the Vital Principle, if it partakes of motion by its own nature. Although, however, it may be in motion by its own nature, it may still be moved by force, and if by force, still by nature; and the same holds good for the state of rest. Thus, the point towards which anything is by its nature moved, serves also by nature for its point of rest, as equally the point to which anything is moved by force serves also, by force, for its point of rest. It is not easy, however, even conjecturally to determine what will be the forced movements and forced states of rest of the Vital Principle—if its motion be upwards it will be fire, if downwards, earth, for such  are the tendencies of those elements; and this conclusion applies equally to the intermediate movements. Since the Vital Principle besides appears to give motion to the body, it is probable that it communicates to the body the motions which it imparts to itself, and, if so, the converse may be true that it communicates to itself the motions which it imparts to the body. Now, the body is moved by translation, so that the Vital Principle should change with the body and be set free from it, either wholly or in its parts; and if this is admitted, it should follow that the Vital Principle, having gone forth from the body, might re-enter, and the consequence of this would be that the dead bodies of animals rise again. Could the Vital Principle be subject to casual motion communicated by some other power than its own, then an animal might be impelled to move by impulse from without; but it is noway necessary that that which is essentially self-motive should be moved by something else, unless by mere chance, any more than that which is good, in and for itself, should be so by or for the sake of something else. It may be confidently affirmed besides, that the Vital Principle, if it do move, is moved by objects which act upon the senses. Although, however, Vital Principle should be self-motive, it would still be in motion, and thus, as all motion is displacement of that which moved, as being moved, the Vital Principle might  be displaced from its essence, unless its self-motion were a casual property; but self-motion is of its very essence.

Some philosophers maintain that the Vital Principle moves the body in which it is, as it is itself moving,—and this is the opinion of Democritus, who expresses himself almost in the words of the comic poet Philippus, who charges "Daedalus with having made a wooden Venus to become movable, when quicksilver was poured into it." Democritus, in fact, says much the same thing when he maintains that indivisible spheres are in motion, from their having been by nature constituted never to remain at rest, and that these spheres drag along with them and give motion to all things. But we will ask Democritus whether it is those self-same spheres which produce the state of rest, and it will be difficult or rather impossible for him to explain how they are to do so. It is not thus, besides, that the Vital Principle appears to give motion to an animal, as it acts, generally speaking, by some kind of election and thought.

It is in this same manner, however, that Timæus physiologically explains how the body is moved by the Vital Principle—that, from its being in motion, the body, with which it has been interwoven, is moved also; and having constituted it out of the elements, and divided it according to harmonic numbers, in order that it may have an innate sense of harmony,  and that the universe may move in accordant orbits, he bent the straight line into a circle, and dividing that circle into two united in two parts, he again divided the single circle into seven others, as if to indicate that the orbits of the sky are the movements of the Vital Principle.

But, in the first place, it is not correct to say that the Vital Principle is magnitude, for Timæus evidently means that this Principle of the universe is such as is the so-called mind; and, then, that Principle of the universe can resemble neither the sentient nor the concupiscent faculty, as neither of these moves in a circle. The mind is one and continuous as is cogitation, and cogitation as are thoughts, and thoughts are, by concatenation, one, in the sense, not of magnitude, but of number; and, therefore, the mind is not continuous in the sense of magnitude, but either it is without parts, or, at all events, not continuous as magnitude. How, indeed, were it magnitude, is it to think—as a whole, or by some one of its parts? But parts must be regarded either as magnitude, or as points, if, indeed, a point may be regarded as a part; and, if parts be considered as points, then, as points are innumerable, the mind, clearly, will never be able to recount them all, and if, as magnitude, the mind will have to dwell very often, or rather continuously, upon the same subject. But it is manifest that thinking may be exercised once for all. If, besides, it  suffice for thinking, that there should be contact by some one of its parts, why should it move in a circle, or why be magnitude? And if necessary for thinking that there should be contact by the whole circle, then what means contact by its parts? How, besides, shall that which has parts think by that which is without parts, or that which is without by that which has parts ? Thus, it follows that the mind must be that circle: for thinking is the movement of the mind, as the periphery is the movement of the circle ; and, if thinking be the periphery of the mind, the mind may be regarded as the circle, of which thinking is the periphery. But then the mind will be ever thinking, and necessarily so, since the peripheral movement is unceasing. Now, there are limits to practical thoughts, (as all such are for the sake of something else,) and so equally there are to speculative thoughts, in their reasons; and every reason is either a definition or a demonstration. Thus, demonstrations set out from a principle, and are, in some way, terminated by a syllogism or a conclusion; and even though not concluded, they do not revert to their principle, but, taking up another mean and extreme, they proceed on ward; but the periphery, on the contrary, does revert to its point of departure. Definitions, however, are always limited. If, moreover, the same periphery recur often, the mind will be driven to think often upon the same subject, and  thinking, besides, seems rather to be a kind of rest and a halt than motion; and this applies equally to the syllogism. As every condition, besides, which is compulsory and ungenial must be unhappy, so unless movement be an essential property of that mind, it must be moving against its nature, and it cannot but be painful for it to have been so connected with the body as to be unable to free itself from it; nay more, it is a lot to have been avoided, since it is better for the mind, as is commonly said, and to many seems reasonable, not to have been connected with a body at all. The cause too, of the circular movement of the sky is obscurely stated—for the essence of the Vital Principle is not the cause of that movement, as it never does, excepting it be by chance, so move, nor can the body be the cause, as it is the Vital Principle rather which gives motion to it; neither is it explained how it is better for the Vital Principle to be so circumstanced, and yet it ought to have been shewn that God had caused it to have a circular movement, as better for it to be in motion than at rest, and to move in that rather than in any other direction. But as this is an inquiry which belongs rather to other studies, it may, for the present, be laid aside.

The same incongruity which occurs in most of the theories upon Vital Principle is met with here, in that writers join Vital Principle to and place it in a  body without having first settled for what purpose the body is to receive it, or how it is fitted for the office. It would seem, however, to be necessary that this should be settled, as it is through this connexion that the one acts and the other is acted upon, that the one moves and the other is moved; and these are relations which cannot be attributed to casual associations. There are writers who content themselves with saying what Vital Principle is, without determining any thing about the body its recipient, as if it were admissible, according to Pythagorean legends, that any kind of Vital Principle might clothe itself with any kind of body; but every thing, on the contrary, seems to have its own particular character and form. Such opinions are, in fact, very much like maintaining that the builder's art may be undertaken with musical instruments; but we affirm that as each art must employ its own instruments, so each Vital Principle must employ its own body.


Another opinion upon the Vital Principle has been handed down, which to many is not less acceptable than any one of those already alluded to, but which, having been scrutinized in our popular disquisitions, has been found to be wanting. The supporters of this opinion say, that the Vital Principle is some kind of harmony; that harmony is a mixture and compound of contraries, and that the body is constituted of contraries. But although harmony is a certain proportion or compound of particles mixed together, it is not possible that the Vital Principle should be the one or the other; for it forms no part of harmony to produce motion, but all writers agree in assigning motive power to the Vital Principle as its most characteristic property. The term harmony, besides, is applicable rather to health and the corporeal powers in general, than to the Vital Principle, as would be very manifest to any one who should undertake to account, by any harmony, for the emotions and functions of the Vital Principle; for it would be scarcely possible to reconcile them to one another. If harmony, besides, may  be spoken of with reference to two points—as applicable, most especially, to the composition of particles in masses which have motion and proportion, whenever they may so coalesce as not to admit of any which are homogeneous, and then as applicable to the proportion of the commingled particles, yet in neither sense can it be reasonable to regard Vital Principle as harmony, nor can the Vital Principle be the composition of the parts of the body: for the composition of the parts (and many and various are the compositions of the parts) is quite open to examination—but of what can we suppose that the mind, or the sentient, or the appetitive faculty is a composition? or how is any one of them to be composed? It is equally absurd to think that the Vital Principle can be the proportion of the mixture, since the mixture of the elements which forms flesh is differently proportioned from that which forms bone. It will happen, too, from this theory, that there are many Vital Principles, and many in every body, if all bodies are from the elements in combination, and if the proportion of the combination is harmony and Vital Principle. We might inquire too of Empedocles, who maintains that each of those bodies exists in a certain proportion, whether Vital Principle is the proportion? or whether rather is it present in the members, as something different from proportion? Is affinity, besides, the cause of a fortuitous or a definite combination of  parts? And then, again, is affinity the proportion, or something besides the proportion?

Such are the difficulties which present themselves; but if the Vital Principle is something different from the composition, what is that which is simultaneously destroyed with the life, in the flesh, and other parts of an animal? Besides these questions, since each of the parts of the body has not Vital Principle, unless the Vital Principle is the proportion of the composition in the parts, what is that which is destroyed when the Vital Principle has forsaken the body? It is then clear, from what has been adduced, that Vital Principle can neither be any kind of harmony, nor be moving in a circle.

But to maintain that the Vital Principle is moved by accident is to maintain, as we have said, that it moves itself as it is moved in that in which it is, and which is moved by it; and that it cannot possibly have locomotion in any other way. It might, however, with greater probability be doubted, and for the following considerations, whether it moves at all—for we are accustomed to say that the Vital Principle is daring or afraid, is angry too, and both feels and thinks, and as all these seem to be motions, it might be supposed that the Vital Principle does move. But yet this is no necessary consequence—for if to grieve, to rejoice or think are motions, in the fullest sense, then each of them is motion, and motion may be said  to emanate from the Vital Principle, as anger or fear is produced by the heart being moved in this or that manner, and thinking may be some analogous or different kind of motion; but some of these phænomena are produced by the displacement of certain particles in motion, and others by change, the explanation of the quality and manner of which is foreign to the present inquiry.

Now to maintain that the Vital Principle is angry is very much like saying that it weaves or builds, and thus it would, perhaps, be better to say, not that Vital Principle pities, learns or thinks, but that the man, by his Vital Principle, is so affected or so engaged. It is not, however, hereby implied that motion is in the Vital Principle, but, on the contrary, that sometimes it proceeds to, and sometimes comes from it; as sentient impression is from external objects, and recollection comes from it to the movements or impressions abiding in the sentient organs. The mind seems to be a peculiar innate essence, and to be indestructible; were it destructible, however, it would, in an especial sense, be so by the dulness attendant upon age, when probably that happens to the mind which takes place in the sentient organs; for if an aged person could take an eye of a certain character, he would see as well as a young man. Thus, the infirmities of age are attributable, not to the Vital Principle having been in aught affected, but to its  recipient suffering, as it does from drunkenness or maladies. Thus, too, thought and reflexion languish when any thing within the body has been destroyed, but that which thinks is impassive. The properties, therefore, of thought, love and hatred belong, not to it, but to that which contains it, and as it contains it; so that when this recipient is destroyed, it can either recollect nor love, as those emotions emanate not from it, but from that which was in common with it, and which has perished. But the mind is probably something more divine, and it is impassive.

It is, then, manifest from what has been adduced, that Vital Principle cannot be in motion; and if altogether without motion, it cannot clearly be self-moved.

The most unreasonable by far of all the opinions upon Vital Principle is that which holds it to be a number with self-motion, for it is beset with insuperable objections; those, in the first place, which result from the idea of motion, and then those more particular objections to speaking of it as a number. How, indeed, is it possible to think of an unit in motion? by what or how, being indivisible and homogeneous, is it to be moved? If said to be both motor and moved, it must have distinction of some kind. Since, besides, they say that a line in motion forms a surface, and a point in line, then units in motion will form lines, as the point is distinguished from the unit  only by position; and thus the number of Vital Principle has already locality and position. If, again, from any number there be subtracted a number or an unit, there remains a different number; but plants and many creatures, after having been divided, live on, and appear still, in a specific sense, to possess the same Vital Principle. It might also be supposed to make no difference whether we speak of the Vital Principle as formed of units or corpuscles; for if points are substituted for the spherules of Democritus and quantity alone remains, there will still be in that quantity, as in all continuity, a motor and a moved; for the theory takes account neither of greatness or smallness, but only of quantity. Thus, there must of necessity be something to impart motion to the units. But if the Vital Principle is the motor in an animal, so must it be in the number, and thus the Vital Principle, being no longer motor and moved, is the motor only. Even admitting that the Vital Principle may, in some way, be an unit, there must still be some distinction between it and other units; but what distinction, save that of position, can there be between one unit and another? If then the units and points which are in the body are different, the units will be on the same spot as the points, for the unit will occupy the place of the point; but what then is there to prevent them from being infinite in number on the same spot, even if there be  only two, as things are indivisible of which the locality is indivisible? But if the points in the body are the number of the Vital Principle, or if the number formed from the points in the body is the Vital Principle, why have not all bodies Vital Principle? Now there seem to be points in all bodies, and those infinite in number. How besides is it possible for the Vital Principles to be separated and set free from bodies, since lines are not divisible into points?


The peculiar incongruity to which we have alluded, belongs as well to those who suppose Vital Principle to be some kind of body with tenuity of parts, as it does to those who with Democritus maintain that the body is moved by the Vital Principle; for if the Vital Principle is in the whole sentient body, then, being some kind of body, there must necessarily be two bodies in one and the same body. And it may be objected to those who speak of it as a number, that if so, there must be many points in a single point, or every kind of body must have Vital Principle, unless it is a number innate and different as well from other numbers, as from the points which are in the body. It results too from this theory, that an animal is moved by a number much in the same way that Democritus, as we have said, gives motion to it; for what matters it whether we speak of spherules, or large units, or units simply in motion? In either case, the animal is compelled to move from their being in motion.  Such and many other such objections may be urged against those who represent Vital Principle as an intimate combination of motion and number; as it is not only impossible therefrom to give any definition of Vital Principle, but we affirm that it cannot even account for one of its accidents. And this would be evident to any one who should attempt, by this theory, to explain the affections and functions of the Vital Principle,—its reasonings, sensations, pleasures, pains, and other such manifestations; for it would be difficult, as we have already said, to form even a conjecture concerning them from it.

Now three modes of defining Vital Principle have been transmitted to us: some have represented it as the most mobile of entities from being self-motive; some as the most attenuated, and others again as the most incorporeal of entities; but we have already reviewed those opinions, and shewn how very questionable and contradictory they are. There remains for us then only to consider in what sense Vital Principle can be said to be derived from the elements. This opinion has been adopted in order to explain how the Vital Principle can perceive and recognise all beings and things; but it necessarily involves many and weighty objections. The supporters of this opinion lay it down as a fact that like recognises like, which is very much like assuming that Vital Principle is, in some way, the things themselves;  but things are never homogeneous, as they contain many other particles besides their own; and many or rather infinite in number are their mutual combinations. Thus even if it be conceded that the Vital Principle may recognise and perceive the elements of which anything is constituted, by what is it to perceive or recognise the thing as a whole, whether it be a man, or flesh or bone? The same question may be put for any other compound body; as the elements, constitutive of every such body unite, not in any fortuitous manner, but in a certain proportion and combination, just as Empedocles expresses himself with respect to bone—"The bounteous earth, in her vast furnaces, out of eight parts has had allotted to her two of liquid light, of fire four, and bones were made white." It would be to no purpose then, that the elements should be in Vital Principle, unless proportion and combination were there also; for although each element may recognise its like, there will still be nothing whereby to recognise a bone or a man, unless such things be present with it also. But it is scarcely necessary to say that this cannot be; for who can have a doubt whether a stone or a man is or is not present in Vital Principle? or good or ill, or any other quality? As the term being, besides, admits of several significations (for it signifies sometimes a particular object, sometimes quantity or quality, or other one of the specified categories), shall it or  not be said that Vital Principle is derived from them all ? Now, there do not appear to be any elements which are common to all the categories. Shall it then be formed only from such elements as pertain to the essence? How, in that case, is it to recognise each of the others? Shall it be said that there are, for each genus, elements and peculiar principles wherewith the Vital Principle may be formed? If so, it will be quantity, and quality and essence; but it is impossible that from the elements of quantity there should be eliminated essence without quantity.

Such and other such difficulties concur to oppose the opinion of those who say that the Vital Principle is formed from all the elements.

It is absurd to maintain that like is unimpressionable by like, and yet assert that like is able to perceive and recognise like by like; and the more so, as these writers set down feeling as they do thinking and recognising, as some kind of impression and motion. But to shew how many doubts and difficulties beset the opinion adopted by Empedocles, that "objects are recognised by the corporeal elements in the relation of like;" we have only to observe that all those parts in animal bodies, which are simply of earth, as bones, sinews and hairs, seem to be altogether without feeling, and consequently without any feeling of like, and yet, according to the theory, they  ought to be perceptive. There will be a larger amount of unconsciousness than perception, besides, allotted to each principle, as each will recognise its own individuals, but be unconscious of the many others—all the others, in fact, which are unlike. It follows, too, from this theory, that the god must be the most senseless of beings, as he alone cannot recognise the element "repulsion," of which all mortal beings cannot but be conscious, since each of them is derived from all the elements.

But wherefore, let us ask, have not all beings a Vital Principle, since every thing is either an element, or derived from one or from more than one, or from all the elements? Thus, it is necessary to every being that it should recognise some one thing, or more than one, or all things. But we are at a loss to know what that is which individualizes things: the elements are like matter; but that, whatever it be which binds the others together, must of all be the most influential. Now, it is scarcely possible that any thing should be more influential and dominant than the Vital Principle, and quite impossible that any thing should be more so than the mind; for it is probable that the mind was the first-born and sovereign in nature, while these philosophers maintain that the elements were the first of entities.

None of these philosophers, however, neither they who maintain that the Vital Principle is derived from  the elements, on account of its recognising and perceiving things, nor they who regard it as the most motive of beings, can be said to speak of every Vital Principle; for all sentient creatures are not motive, as there are animals which appear to be fixed abidingly to the same spot, and yet locomotion seems, according to these philosophers, to be the only motion imparted to animals by the Vital Principle. They, too, equally err who form mind and sensibility out of the elements—for plants appear to be alive, without partaking either of locomotion or sensibility; and many animals have no understanding. But even if we may pass over these objections, and admit that the mind as well as the sensibility may be a part of the Vital Principle, still no general theory could be framed for every Vital Principle, or for it as a whole, or for it individually. Thus, the reasoning in the so-called Orphic verses has been stamped with this same error, for the poet says that "the Vital Principle, borne by the winds, enters from the universe into animals during respiration." But this cannot possibly be applicable to plants or to some animals, since there are some which do not breathe. This fact, however, had escaped the attention of those who first adopted the hypothesis.

But even if it be well to form the Vital Principle out of the elements, it by no means follows that it should be out of them all, as one or other part of the  contraries is able to judge both itself and its opposite. Thus, by the straight we know both the straight and the curve, as the ruler is the judge of both, while the curve is the judge neither of itself nor the straight.

There are writers who maintain that the Vital Principle has been diffused through the universe, whence probably Thales was led to think that all things are full of gods. But the opinion is not without its difficulties. Why, it may be asked, does not the Vital Principle, when in the air or fire, form an animal rather than when in the elements in combination, although seemingly more generally situated in either of those elements alone? It might also be inquired why the Vital Principle, which is in the air, is more exalted and more enduring than that which is in animals. On either side, in fact, we are met by absurdity and contradiction; for it is very unreasonable to speak of air and fire as animals, and absurd to say that they are not so when Vital Principle is conceded to them. Those philosophers, in fact, seem to have assumed that Vital Principle is in those elements, because the whole ought to be specifically as its parts; and so it was forced upon them to admit that Vital Principle must be, specifically, the same as its parts, if creatures become living creatures by taking in something from that which surrounds them. But if the air, however subdivided, is still homogeneous,  and the Vital Principle heterogeneous, it is clear that some one of its parts will, and some other will not be, in the air; and thus either the Vital Principle must be homogeneous, or else it cannot be present in every part of the universe. It is manifest, then, from what has been adduced, that the faculty of recognising does not belong to Vital Principle by virtue of its being derived from the elements; as also that it cannot with accuracy or truth be said to be self-motive.

Since the faculties of knowing, feeling and thinking, together with desiring, willing and the appetites generally, as also locomotion, growth, maturity and decay, are properties of the Vital Principle, let us inquire whether or not each of those properties is imparted to us by the Vital Principle as a whole—that is, does each of those faculties emanate from the Vital Principle as a whole? do we think, feel, act and suffer by it as a whole, or are different offices assigned to different parts? Is life in one, or more than one, or in all the parts, or is there some other cause for life than the Vital Principle?

Some writers maintain that Vital Principle is divisible, and that by one part it thinks, and by another feels desire; but what then, if it be naturally divisible, holds its parts together? Not the body certainly, we answer; for the Vital Principle, on the contrary, appears to hold it together, as from the moment of its departure the body expires and decays.  If there be a something which makes it one, that something is, in the strictest sense, Vital Principle; and it will be necessary again to inquire whether that something is indivisible or with parts; if it be indivisible, then why not at once conclude that it must be Vital Principle? If it be divisible, reason will again seek to learn what that is which holds its parts together; and thus may the inquiry be continued interminably. With respect to the parts of the Vital Principle, it is difficult to determine what is the part which has been assigned to each of them in the body; for if it is the whole Vital Principle which sustains the whole body, it is probable that each of its parts sustains some one part of the body. But this is very like an impossibility; for it would be difficult even to conjecture what part the mind could connect with others, or in what way it could do so at all. Thus, plants, when divided, appear to live, and so do some species of insects, as if possessing still the same Vital Principle in a specific, although not in a numerical sense; for each of the parts has sensation and locomotion for a time, and there is no room for surprise at their not continuing to manifest those properties, seeing that they are without the organs necessary for the preservation of their nature. Nevertheless, in each of those parts coexist all parts of the Vital Principle, and those parts are, specifically, the same with each other, and with the whole—with each other, as  being inseparable, and with the whole as being separable. But the living principle in plants seems to be a kind of Vital Principle, for animals and plants alike partake of it; and it is separable from the sentient principle, but yet without it no creature can possess sensibility.


THUS have the opinions handed down by former writers upon Vital Principle been delineated; and now let us retrace our steps, and again, as if at the outset of our inquiry, endeavour to define what it is and what the most general expression for it.

We say, then, that essence is a particular genus of entities, and that of it part is matter, which in itself is not any one particular object, as it is other than form and species from which each object derives its particular denomination; and that, in the third place, there is the derivative from both these. Now matter is potentiality,species reality, and that in a twofold acceptation, as knowledge and as reflexion; but bodies, and above all natural bodies, seem to be essences; for they are, in fact, the origins of other bodies. Among natural bodies some have and some have not life; and by life we mean the faculties of self-nourishment, self-growth and self-decay. Thus,  every natural body partaking of life may be regarded as an essence; but then it is an essence in combination, as has been said. And since the body is such a combination, being possessed of life, it cannot be Vital Principle; for as it is itself more truly subject and matter, it cannot be among the subordinates of a subject. It follows, then, that the Vital Principle must be an essence, as being the form of a natural body holding life in potentiality; but essence is a reality,—the reality, that is, of a body such as has been described. Now reality is, in the twofold signification, either of knowledge or of reflexion; and that it may be regarded as knowledge is manifest in that sleep and watching co-exist as original properties, in Vital Principle; and equally manifest that watching is analogous to reflexion upon knowledge, as that sleep represents knowledge possessed but not employed. But knowledge pre-exists in the same individual, and the Vital Principle is, therefore, the original reality of a natural body endowed with life in potentiality; only this is to be understood of a body which may be organised. Thus, the parts even of plants are organs, but then they are organs which are altogether simple, as the leaf is the covering of the pericarp, and the pericarp of the fruit; and the roots are analogous to the mouth, for both take in food. If, then, there be any general expression for every kind of Vital Principle, it may be set down as "the  incipient reality of a natural body which is organised"

It is, therefore, to no purpose to inquire whether Vital Principle and the body are one, any more than whether wax and the impress upon it are one, or whether the matter formative of any object and the object formed are one ; for one and being have many significations, but they are correctly designated as reality.

It has thus been explained generally what the Vital Principle is, and shewn that it is an essence, in its abstract signification, which implies the particular mode of being in any particular body, as if any instrument, an axe, for instance, were a natural body, the mode of being in the axe would be, at once, both its essence and its Vital Principle; for, were it once to be withdrawn, then, save in name, it could be an axe no longer. All this, however, relates to an axe, but Vital Principle is the mode and the cause of being, not in any thing like an axe but, in a natural body, having within it a principle of motion and of rest.

But what has been said may be better understood by reference to the parts of a body. Thus, if the eye were an animal, vision would be its Vital Principle, as vision, abstractedly considered, is the essence of the eye; but the eye is the matter of vision, and if vision be wanting, then, save in name, it is an eye no  longer, any more than is that an eye which is represented in sculpture or painting. All that has here been assumed of a part may be made applicable to the whole living body; for, as there is an analogy between part and part, so is there between the whole sensibility and the whole sentient body, in the ratio of its sensibility ; but this must be understood of a body which yet retains its Vital Principle, and is, in potentiality, alive. The seed and the fruit are the representatives of such a body in potentiality ; and as cutting is the reality of an axe, vision that of an eye, so watching is the reality of Vital Principle ; which is to the body what vision is to an eye, and its own property to any instrument ; but this is to be understood of a body in potentiality. Thus, as an eye is a pupil and vision, so an animal is a body and Vital Principle.

It is then obvious that neither Vital Principle nor any of its parts, even granting that it may be divisible, can be separate from the body; for of some of its parts it is the reality; and yet there is nothing to preclude the possibility of some others being separate, as there are some which do not contribute to the reality of any body. It is doubtful, however, whether the Vital Principle is the reality of a body in the sense that a mariner is of his vessel.

Thus far, then, have we proceeded in our attempt to define and delineate Vital Principle.


Since that which is evident and, when abstractedly considered, more apprehensible may be derived from particulars which are by their nature obscure, although to us more apparent, let us again attempt, bearing this in mind, to attain to a comprehensive view of Vital Principle. It is not only correct that the wording of a definition should shew, as do most definitions, what a thing is, but it ought also to embody and make apparent the cause of its being what it is. But the terms usually employed make definitions to be kinds of conclusions; as if, for instance, to the question "what is a quadrature?" it be answered, that it is to find an equilateral rectangular figure equal to another figure with unequal sides, such a definition is the statement of the conclusion; if it be said that the quadrature is "the discovery of a mean proportional," this conveys the cause of the thing.

We say, then, resuming our inquiry at its outset, that the animate is distinguished from the inanimate by having life. Now the term life has many  acceptations but if one only of the following properties, viz. mind, sensibility, locomotion, and rest, as well as the motion concerned in nutrition, growth, and decay be manifested in any object, we say that that object is alive. And, therefore, all plants seem to be alive, for they all appear to have within them a faculty and a principle by which they acquire growth and undergo decay in opposite directions; for they do not grow upwards exclusively, but they grow equally in both these and all other directions, and are alive throughout so long as they are able to imbibe nourishment. It is possible for nutrition to subsist independently of the other functions, but the others cannot possibly, in mortal beings, subsist without it; and this is manifest in plants, since no other than it has been allotted to them. Thus, it is by this faculty of nutrition that life is manifested in living beings, but an animal is characterized above all by sensibility; for we say that creatures endowed with sensibility are not merely living beings but animals, although they may neither be motive nor change their locality. Touch is the sense first manifested in all creatures, and, as the nutritive faculty can be manifested independently of Touch and other senses, so the sense of Touch can be manifested independently of any other. We call nutritive function that part of Vital Principle of which plants partake; but all animals appear besides  it to have the sense of Touch; and we shall, hereafter, explain why each of those functions has been allotted. Let it suffice, for the present, to say that Vital Principle is the source of the nutritive, the sentient, cogitative and motive faculties; and that by them it has been defined.

It is easy, with respect to some of those faculties, to perceive, whether any one of them is the Vital Principle, or a part of Vital Principle, and if a part whether it is distinct from other parts substantively, or in an abstract sense only; but there are others which seem to elude investigation. Thus, as some plants appear, after having been divided, and after the parts have been separated, still to be alive, as if the living principle, in each plant, were in reality one, in potentiality more than one, so we see the same occurrence in other distinctions of the Vital Principle, as in insects which have been divided; for each of the parts manifests sensibility and locomotion, and if sensibility, then imagination and desire, as wherever there is feeling, there must be sense of pain and pleasure, and wherever these, there must, of necessity, be desire. We have nothing very certain to offer upon the subject of the mind and the reflective faculties; but the mind seems to be another kind of Vital Principle, and alone to be capable of existing apart from the body, as the everlasting exists apart from the  perishable. Thus, it is manifest, from what has been adduced, that the other parts of the Vital Principle are not, as some say, distinct from the body, although it is clear that, when considered absolutely, they are different from it; for the mode of being in a sentient must differ from that in a cogitative being, since feeling differs from thinking, and this applies equally to other functions and faculties. All those faculties besides belong to some animals, particular ones only to others, and there are others to which one only has been allotted, and this constitutes distinctions among animals, the cause of which shall hereafter be considered. But something very like this has taken place with respect to the senses, for some animals have them all; others have particular ones only, and there are others again which have but one; but that one is Touch, which of all is the most necessary.

As that by which we live and feel, like that by which we understand, has a twofold signification, since we speak of that by which we understand sometimes as Knowledge, and sometimes as the Vital Principle, for we say that we understand by either of them ; so equally does this apply to that by which we are in health, and which sometimes refers to a particular part of the body, and sometimes to the whole body. Now, the two faculties alluded to,  knowledge and health, are a form, a " specific something", a " relation," and an action, as it were, of a recipient, capable in the one case of knowing, and in the other of maintaining health (for the action of creative energies seems to be innate in the impressionable and suitably constituted subject), but the Vital Principle is that by which we live, feel and think, from life's outset; so that, although it may be the cause and form, it cannot be matter and subject. Thus, the essence has a threefold signification, as we have said, in the sense of form, of matter, and the compound of the two; and of these matter is potentiality, and form reality ; and since the living being is a compound of the two, the body is not the reality of the Vital Principle, but it, on the contrary, is the reality of a particular kind of body. On which account it is happily assumed by some that the Vital Principle can neither be without the body, nor be itself a body of any kind; for a body it is not, but yet it is something of the body, and, therefore, present innately in the body, and that peculiarly constituted. It is not, that is, in any kind of body, as the earlier writers have maintained, when they attached it to a body without in the least defining either the nature or quality of the body; although it must be against all probability that any kind of recipient should receive any thing taken by chance. But here all takes place as might  reasonably be expected—for the realising influence exists congenitally in its own subject, while yet potential, and constituted of matter fitted for its agency. It is then manifest, from what has been adduced, that the realising influence and cause can act only upon that which is potentially capable of becoming such or such a reality.


All the faculties of Vital Principle which have been enumerated belong, as we have said, to some creatures, some only of them belong to others, and there are creatures again which have but one; and we spoke of those faculties as the nutritive, appetitive, sentient, locomotive and cogitative. Of these, the nutritive alone belongs to plants; but to other beings both it and the sentient have been imparted; and if the sentient, then the appetitive, for appetite is desire, passion and volition; and all animals, without exception, have the sense of Touch. But the creature to which sensibility has been imparted cannot but be sensible of pleasure and pain, of what is grateful and what painful; and if sensible of these, it must have desire, as desire is the appetite for what is grateful. All such creatures, moreover, have the sense for food, as they have Touch, which is that sense; for all animals are nourished by what is dry and moist, warm and cold, and Touch is the sense for judging of these qualities. But it is only by chance that the Touch can judge of other qualities, as neither sound, colour nor odour contribute in aught to nourishment; and savour is among tangible qualities. Hunger and thirst are desires: the former for what is dry and warm, the latter for what is liquid and cold ; and savour is the condiment, as it were, for both. As, however, we shall be more explicit upon those points hereafter, it may, for the present, suffice to say, that all such creatures as have the sense of Touch have appetite ; it is uncertain whether or not they have imagination, but this also shall be considered hereafter. There are creatures to which, besides those faculties, locomotion has been imparted; and others again, as man, to which have been allotted both reflexion and mind, together with any other and yet nobler faculty, if such there be, than mind.

It is clear, then, that there can be but one definition for Vital Principle, as there is but one for a geometrical figure; for as in geometry there is no figure but the triangle and its sequences, so neither are there any kinds of Vital Principle save those which have been enumerated. Could there, however, be any such common expression for figures, as without being peculiar to any one, should yet be applicable to all, so might there be for the Vital Principles alluded to. It would be idle, however, to seek for any such expression, in the case either of Vital Principles or geometrical figures, as should neither be applicable to any one of them individually, nor, putting aside individuals, be applicable to them as an individual species. But still there is an analogy between the faculties of Vital Principle and geometrical figures; for as in vital properties, so in geometrical figures, the antecedent is ever present potentially in the sequences, and as the triangle is in the square, so the nutritive is in the sentient faculty. Thus, the inquiry must be conducted with reference to individuals, in order to learn what is the Vital Principle of each, as of a plant, a man, or a brute; and wherefore beings are thus ranged in a series.

Without the nutritive function there can be no sensibility, but in plants the nutritive exists without the sentient; so again without the Touch there can be no other sense, while Touch can exist alone, for many animals have neither sight nor hearing, and are altogether without smell. Among sentient creatures some have and some have not locomotion, and, finally, to a few calculation and judgment have been imparted; and to such among mortal beings as are so endowed all other faculties have been imparted likewise. But to such as possess some one only of the faculties, calculation has not been allotted, as some of them have not even imagination, while others live by it alone; it would be foreign to our present inquiry to enter upon the speculative intellect.

It is, then, clear that the definition which comes closest to each one of those faculties is also the fittest for the elucidation of Vital Principle.


It is necessary, in order well to study those faculties, that we should comprehend what each of them individually is, and then, in like manner, carry our inquiry into their consequences and other conditions. But if it behove us to say what each of them is, as what is the cogitative, sentient, or appetitive faculty, it should previously be settled what that is which thinks and that which feels; for energies and acts are, abstractedly considered, pre-existent to their functions. Granting, however, that it is so, and that we ought, before the faculties or functions, to have considered their opposites, it might be fitting here also, and for the same reason, first to define the opposites of the functions define, that is, food before nutrition; the object before perception; and the intelligible before thought.

Thus we must first speak upon nutrition and generation, for the nutritive faculty is innate in other beings besides animals; it is the primal and most universal influence of the Vital Principle, and through it life is manifested in all beings. Its functions are to generate and to employ nourishment; for the most  natural of the functions in beings which are perfect, that is, which are neither dwarfed nor spontaneously generated, is to produce another such as itself, an animal an animal, and a plant a plant, in order that they may partake, to the extent which has been allotted to them, of the Everlasting and the Divine. All creatures yearn after this, and, for the sake of it, they do all that they do naturally ; but since such beings cannot, in uninterrupted continuity, partake of the Everlasting and the Divine, because no perishable being can abidingly continue as one and the same ; yet each can partake thereof in its own allotted portion, be it larger or smaller, and still continue, if not the same, like the same, and one, if not in number, as species.

The Vital Principle is the cause and the origin of a living body. Now, cause and origin have several significations; for the Vital Principle is equally a cause, according to any one of the three defined modes of causation: as that whence motion proceeds; as that for which motion is produced; and cause, again, as the essence of living bodies. It is evident that it is a cause as an essence, since the essence is in all things the cause of their being what they are; and as life is the mode of being in living beings, so Vital Principle is the cause and the origin of all such. It is the realizing principle, besides, the cause that is of something which exists in potentiality becoming a  reality. It is manifest, too, that Vital Principle is a cause, in the sense of a final cause; for as the mind acts for some end, so does nature, and that end is her aim; and such an aim has the Vital Principle, by its nature, in living bodies. Thus, all natural bodies, those of animals as well as those of plants, are its instruments, and are what they are for its purposes. The term final cause has a twofold signification, as it implies that for which, as well as that by which, any result is obtained; and Vital Principle is a, final cause, as that whence locomotion is derived, although this is a property which does not belong to all living creatures. Change and growth, moreover, are dependent upon Vital Principle; for sensation seems to be a change of some kind, and whatever is sentient has Vital Principle; and this applies equally to growth and decay, for nothing grows or decays naturally unless it be nourished, and nothing is nourished which does not partake of life. Empedocles has not expressed himself happily upon this point, as, after other observations, he adds that plants take growth downwards, where they strike root, from this being the natural direction of earth, and upwards, from this being the natural direction of fire. Neither has he clearly seized the import of the terms upwards and downwards, as they are not identical for all creatures, or for the universe; for the nead is to animals what the roots are to plants, if we may speak of organs  after their functions, although in other respects different. But, besides these objections, what is that which is to hold fire and earth, with their opposing tendencies, together? Now, unless there be a restraining force, they must be torn asunder, and if such there be, it ought to be regarded as Vital Principle, and the cause both of nourishment and growth.

The nature of fire seems, to some philosophers, to be the absolute cause of nutrition as well as growth, and that because it alone, among bodies or elements, appears to be nourished and to grow. It might, therefore, be assumed, that it is fire which works out those processes in plants and animals; but although fire is possibly a joint cause, it cannot be the exclusive cause, as this must be assigned rather to the Vital Principle. The increase of fire is infinite, so long as there is any thing combustible, but to all the bodies of nature's constitution there is a limit and a relation both as to bulk and increase; and these are conditions, not of fire but of Vital Principle; not of matter but of design.

Since the same faculty of Vital Principle is at once nutritive and generative, it is necessary first to define nutrition ; for it is by this, compared with other faculties, that Vital Principle is especially distin- guished. Nutrition, then, appears to be a contrary acted upon by a contrary, but this does not imply any kind of contrary by any other contrary; it refers only  to such contraries as can generate from and give growth to one another. Thus, there are many things derived from one another which are not always quantities, as the healthy, for instance, is derived from the unhealthy; neither do these contraries appear, in any manner, to be nourishment for one another, as water, for instance, is nourishment for fire, but fire is not nourishment for water. It is in homogeneous bodies especially, that the contraries seem to be in the relations of nourishment and nourished. But here there is a difficulty; for while some maintain that like is nourished as it is increased by like, there are others who maintain, as we have said, that it is contrary which is nourished by contrary; that like is unimpressionable by like; that food undergoes change and is digested, and that all-change implies conversion to an opposite or an intermediate state. Nourishment, besides, is affected by the body which is nourished, although the body is not affected by the nourishment, just as the material is affected by the artisan, although he is not affected by the material; for it is the artisan alone who converts the material from a raw state into one of usefulness. There is, however, a distinction to be observed in nourishment, between its last and adventitious or its first state; if both states are nourishment, distinguished only by the one being undigested, and the other digested, then it may be correct to admit of both explanations for nutrition; for in so  far as food is undigested, it is contrary nourished by contrary, and in so far as it is digested, it is like nourished by like. Thus, it is manifest that both these opinions are in one sense right, and in another wrong. But as nothing can be nourished which does not partake of life, so a living body may be regarded as a body which is nourished from having life; and thus nutrition is not in a casual, but a positive relation to a living body. There is an obvious distinction between nourishment and growth: in so far as a living body is quantity, it is capable of growth, and in so far as a something is matter and essence, it is nourishment; for it preserves the essence of the body, which exists so long as it can be nourished. Nourishment, however, does not generate that which is nourished, as it is the same as it; for it is already itself the essence, and nothing can generate, although it may preserve itself. Thus, it is the same faculty of Vital Principle which is able to preserve that, such as it may be, which contains it, and it is nourishment which renders it fit for its office; and, therefore, when deprived of nourishment, it can exist no longer.

Now, there are here three things or conditions—something to be nourished, something by which nourished, and something which nourishes. That which nourishes is the primal or nutritive faculty; that which is nourished is the body; and that by which nourished is food. And as things are correctly  designated after the object to which they tend, and as the object here is to generate another like itself, so the primal faculty may be set down as being generative of another like itself. That “by which nourished” has a twofold signification, as has that by which a vessel is steered, and which implies hand and rudder, of which the one only moves, while the latter both moves and is moved. It is necessary to nutrition that food should admit of being digested, and as it is heat which works out digestion, so all living creatures have heat.

It has thus then be shewn, although but superficially, what nutrition is; but the subject shall be further elucidated in other treatises upon the subject.


Let us now proceed, as those subjects have been scrutinized, to speak upon sensation in its widest acceptation.

Sensation is the combined result, as has been said, of a motion and an impression, for it seems to be some kind of change; and some writers maintain that it is only like which is impressionable by like, but we have already, in our treatises “upon action and impression,” shewn how far the opinion is or is not tenable. But it is difficult to understand why there is no sensation from the senses of themselves, that is, why, without the presence of external objects, the senses do not give out sensation, although fireearth, and the other elements, from which or the accidents of which sensation is derived, are present in them. It is evident that it is because the sensibility is not in a state of activity, but is only in potentiality; and, therefore, that it is with it as with a combustible material, which alone, without something on fire, does not burn; for otherwise it might set fire to itself, and would stand in no need of fire, in reality, for the purpose. Since we speak of sentient perception in a two-fold  sense, (for we speak of one who hears and sees, in potentiality, as “one hearing and seeing,” although he may happen to be asleep, and we say the same of one who is actually employing those senses,) so may sensation be spoken of in two ways, as subsisting in potentiality and subsisting in activity. Let us, however, before proceeding further, observe that impression, motion, and action are for us equivalent terms—for motion is a kind of action, although an action which is incomplete, as has been elsewhere explained. Now, all things which are impressed and set in motion are so affected by something capable of making impression and existing in activity; so that impression is in one sense by like, and in another sense by unlike, as we have said—for the unlike is subject to impression, but, having been impressed, it is converted into like. A distinction, however, must be drawn between the terms potentiality and reality, for we are now going to employ them in an absolute sense—any individual whatever, then, may be learned, as we might speak of any man as learned, because man is among beings capable of learning and being learned; and so we speak of a man as learned, from his actually professing, at the time, grammatical or other knowledge.

Thus, each of these individuals is learned in potentiality, although in a different manner—the one is so because he is of a certain genus and peculiar  matter; and the other, because he can when he will reflect upon his knowledge, provided there is no external impediment to his doing so. It is this one only, however, when actually reflecting upon his knowledge, being in activity, and fully acquainted with some one subject, as A. for instance, who is to be accounted learned in reality. Both those first men, in fact, are learned in potentiality; but the one is so from having been modified by learning, and undergone frequent changes from one habit to an opposite one; and the other is so from possessing sensibility or rudimentary learning, and being able, although in a different manner, to pass from inertia to activity.

But the term impression is not absolute in signification, as sometimes it implies a kind of destruction by a contrary, and sometimes it signifies rather preservation of something being in potentiality by something which is in reality and like, in the relation that potentiality bears to reality. Thus, the possession of knowledge implies the power of reflecting upon it, and this either is not change, being but an increase of knowledge and a step towards its completion, or it is change of a different kind. It is not correct, therefore, to say that an individual, when thinking, is undergoing change, any more than that a builder, when employed in building, is undergoing change;so that the process by which an individual passes, as to his thinking and reflecting faculties, from potentiality to  reality, ought to have some other appellation than that of instruction. We may not then, as has been observed, say of the individual who, from being in potentiality, learns and receives knowledge from one who is in realityand able to teach, that he suffers impression, or else it must be admitted that there are two modes of change, one in privative dispositions, and another over habits and nature. The first change, however, of this kind in the sentient being comes from the parent at the moment of conception; as from that moment the being has, as it were, learning and sensibility. There is an analogy between the state of activity and reflexion just alluded to, but with this difference, that the impressions productive of activity, as the audible, the visible, and others, are all derived from without; and the cause of this is that sensation, in activity, is employed upon particulars, knowledge upon universals; and universals are, in some way, in the Vital Principle itself. The act of thinking, therefore, is dependant[1] only upon the will of the individual, which is not the case with sentient perception, as for it there must of necessity be objects to be perceived; and this holds good, and for the same reason, with respect to the sciences which are engaged upon external objects, because all such objects are among particulars, and are external to the percipient. But an opportunity may hereafter present itself for the further elucidation of the subject.  Let it, for the present, suffice to say, that the expression being in potentiality has not an absolute signification, for it may be understood of a boy as being qualified potentially to be a General, and also of an individual of suitable age for the office; and the term sensibility is subject to like modifications of meaning. But as the distinction between these two states of sensibility is without any special appellation, although it has been shewn that there is a distinction between them and what the distinction is, it has been found necessary to employ the terms impression and change, as if their signification were unequivocal; but, as has been said, the sentient principle is, when in potentiality, analogous to the external object when in reality.

The sentient principle, in fact, suffers impression when unlike; but, having been impressed, it is converted into like, and becomes the same as that by which the impression is made.


Let us, before proceeding further, speak upon the objects of perception in relation to each of the senses. The object of perception is spoken of in a three-fold manner, as there are two ways in which we speak of perceiving objects distinctly, and one in which we speak of perceiving them accidentally; and of those two ways one signifies the property which is peculiar to each sense, and the other the property which is common to all the senses. I mean by peculiar property that which cannot be perceived by any other than its own sense, and concerning which that sense cannot be deceived—as colour for sight, sound for hearing, and savour for taste. The touch, indeed, discriminates several differences of quality, but every other sense distinguishes only its own subjects; and thus sight or hearing is never deceived as to whether it is colour or sound which is seen or heard, although it may be deceived as to what or where the coloured, what or where the sonorous body may be.

Such then the properties which are said to be peculiar and to belong to particular senses; but there  are properties, such as motion, rest, number, form and magnitude, which are termed common, as they belong not to any one sense, but to all in common. Thus, there is a movement which is perceptible both by Touch and Sight. An object is said to be perceived accidentally when, for example, something white may be the Son of Diares—for the percipient is sensible of the individual accidentally, because of his being an accident of that which is perceived; and, therefore, no impression is made by that which is perceived, as a special object, upon the percipient.

The properties of bodies, which are in themselves perceptible, are, strictly speaking, peculiar properties; and to such each particular sense is naturally and essentially related.


The visible is that for which vision is the sense, and the visible is both colour and something which is describable by words, although it happens to be without a name; but our meaning will become clear to those who accompany us in the inquiry. The visible is colour, and colour is that which is upon something visible in itself; and this something is visible, not only after its appellation but, because it has in itself the cause of being visible. All colour is motive of the diaphanous, in activity, and to be so motive is the nature of colour. On which account nothing is visible without light, but the colour of each object is visible in the light; and we must, therefore, first say what light is. There is a something diaphanous, and I call diaphanous what is visible, and yet not visible,  strictly speaking, in itself, but made visible by colour, which is foreign to it. Such is air, and water, and many solid bodies; yet neither air nor water, as air or water, is diaphanous, but the same nature is present in both those elements, which is in the eternal supernal body. Light is the active state of that same diaphanous, in so far as it is diaphanous, and darkness is the same in its state of potentiality. But light is the colour, as it were, of the diaphanous, when made diaphanous in reality by fire, or other such element as the supernal body; for to it belongs a something which is identical with fire. We have thus said what is the diaphanous and what light, and have shewn that neither of them is fire, nor a body, strictly speaking, nor an emanation from a body, (as, in that case, they would be corporeal), but that they are the presence in the diaphanous of fire or something analogous to fire, since two bodies cannot possibly coexist in one and the same body.

Light seems to be the opposite to darkness; and as darkness is the absence of a particular state of the diaphanous, it is evident that the presence of that state must be light.

Thus Empedocles, or whoever else may have held the same opinion, was wrong in supposing that light was transported and manifested, without our consciousness, between the Earth and surrounding space; for the opinion is opposed as well to sound conclusion  as to observation of the phenomenon. If the interval were small, the fact might, indeed, escape us; but, extended as it is from the East to the West, the postulate is too extravagant to be admitted.

Now that which is without colour is receptive of colour, as that which is without sound is receptive of sound; and that which is without colour is the diaphanous and the invisible or scarcely visible, such as darkness seems to be. Such too is the diaphanous; but then it is the diaphanous, not in potentiality but, in reality; for the same nature is sometimes darkness and sometimes light. But all objects are not visible in light, as there are some of which the peculiar colour only of each is visible; for some, not visible in light, produce sensation in the dark, as certain fiery brilliant appearances (which have no special appellation,) which emanate from fungi, horn, scales and eyes of fishes, but the peculiar colour is not seen of any one of those objects. It is foreign to our present purpose to explain how such objects become visible; but this much is manifest, that it is colour which is visible in light. Therefore, without light colour is not visible; for it is an essential property of colour to be motive of the diaphanous in activity, and the reality of the diaphanous is light. As proof of this, if any coloured object be placed over the sight, the object will not be seen, and yet there is colour, which is motive of the diaphanous, the air, that is, and, by  its being continuous between the object and the sense, it is able to give motion to the visual organ. Thus, Democritus was wrong in thinking that if the medium were a void, vision would be so accurate as to render an ant visible in the sky. The opinion, in fact, involves an impossibility; for vision is produced by some kind of impression upon the visual organ, and as this cannot possibly be effected by the colour which is visible, there remains only that it must be by the medium, and thus a medium there must be; so that if there were a void, vision would be, not to say inaccurate but, altogether precluded.

It has thus then been said why colour must be visible in the light; but fire is visible both in darkness and in light, and necessarily so, since it is by fire that the diaphanous becomes diaphanous. The same reasoning holds good for sound and for odour, as nothing sonorous or odorous can produce sensation when in immediate contact with the sentient organ; but by odour or sound the medium is set in motion, and by it the organ is moved. Thus, when any thing sonorous or odorous is placed immediately upon the sentient organ, no sensation is given out; and this is the case with the sense of Touch, although less evidently so; but the cause of this shall be explained hereafter. The air is the medium for sounds, while that for odour has no special appellation, for there is a particular impression common to air and water; and  what the diaphanous is to colour that which is in those elements is to odorous bodies, as aquatic animals appear to be sensible of odours. But neither man nor animals which breathe can smell without inspiring; and the cause of this shall be spoken of hereafter.


LET us now proceed to determine the nature of sound and hearing. Sound is double—one actual and another potential; for we say that some substances, such as sponge and wool, are without sound; and that others, as brass, and bodies which are hard and smooth, have sound, because such objects are able to sound; are able, that is, to create actual sound by the action of the medium between the object and the hearing. Sound of the actual kind is the invariable result of something in relation to something and in something; for its producing cause is percussion. It is impossible, therefore, that sound should be produced when there is only one substance, as that which percusses must be distinct from that which is percussed; so that the sonorous object sounds by its relation to another object. But there can be no percussion without movement, and sound is not produced by the percussion of any kind of substance, as we have said, (since wool, however percussed, does not, while brass and smooth and hollow bodies—brass because it is smooth—do give out sound,) and hollow bodies create, by reflexion, many percussions after the  first, owing to the medium within them having been set in motion and being unable to make its escape. Sound is audible in air, and so it is in water, although less distinctly; but neither air nor water is the efficient cause of sound, as for it there must be percussion of solid bodies against each other and against the air, and this is effected whenever the air, having been percussed, remains, is not, that is, dispersed. Thus, if the air be struck sharply and forcibly it gives out sound; for the motion of that which percusses should anticipate the dispersion of the air, as if any one were striking a rapidly moving heap or cloud of sand.

An echo is produced whenever the external air has been more than once repelled by the air contained within a vessel, by the sides of which that air is precluded from being dispersed, just as a ball rebounds. It seems as though an echo ought to be a constant occurrence, although it may not be audible, since that happens to sound which happens to light, and light is continually undergoing reflexion (for, otherwise, as light could not be everywhere, darkness would prevail beyond the spot illumined by the sun), but yet it is not everywhere reflected, as it is from water or brass or any other smooth body, so as to form a shadow whereby we are able to distinguish the light itself.

A Void is rightly said to be the sovereign cause of hearing;—for the air seems to be a void, and the  air, when moving continuously and as one body, is creative of hearing. But, owing to its being very diffluent, it gives out no sound, unless that which is percussed be smooth; when this, however, is the case, the air becomes simultaneously one over the surface, as the surface of every smooth body is one. Every sonorous body is so constituted as to set in motion the air which, by continuity, is one up to the hearing, and the hearing is naturally connected with the air; and owing to sound being in the air, the air which is without sets in motion that which is within. An animal, therefore, does not hear everywhere, neither does the air penetrate everywhere; for the part to be set in motion is a living part, and does not everywhere contain air. The air itself, owing to its ready diffusibility, is without sound; but, when precluded from being dispersed, its motion is productive of sound. The air which is within the ears has been so immured as to be immovable; and this in order that the sense may perceive accurately all variations of its movement. It is for these reasons that we are able to hear when in the water, as the water cannot gain access to the congenital air, or pass into the ear through the convolutions; when, however, this does happen, there is no hearing, any more than there is when the membrane of the ear, which is to it what the skin over the pupil is to the eye, is diseased. But proof is afforded whether the hearing is perfect or not, in that the ear  is constantly giving out sound, just as a horn does; for the air within the ears is continually moving in some peculiar manner, and yet sound is foreign to that air and forms no part of its properties. It is on this account, however, that we speak of hearing by a void and something resonant, because we hear by the part which contains the air confined within it.

But is it that which percusses, or that which is percussed, which gives out sound ? Or do both contribute to its production, each in its own way? Now, sound is the motion of something which admits of being moved after the manner of bodies rebounding from smooth surfaces, whereon they may have been impelled. But every kind of body, whether percussing or percussed, does not, as has been said, give out sound ; as when a sharp point, for example, strikes a sharp point, there is no sound; but in order to produce sound, that which is percussed must be so smooth, that the mass of air upon its surface may rebound from, and be agitated over it. The distinctions among sonorous bodies are revealed in the actual sounds which they give forth; for as without light colours are not visible, so without sound the acute and grave are not audible. These terms (acute and grave) are derived from tangible properties, and employed, in a metaphorical sense, for sounds; for the acute moves the hearing quickly and sharply, the grave moves it slowly and dully; not, however, that  the acute is quick or the grave slow; but that such is the motion of the one from the celerity, and such the motion of the other from the tardiness of its operation upon the sense. And there does seem to be an analogy between those sounds and the sharp and blunt, as perceived by the Touch; for the sharp pricks, and the blunt pushes, as it were, because the motion exerted by the one is rapid, by the other tardy; and it is in this manner that the terms in question have originated. Let us here, however, close our observations upon the nature of sound.

The voice is a sound produced by a living creature; for nothing inanimate speaks, although there are objects, such as the flute, lyre, and others, which, having range of note, harmony, and expression, are said, from a resemblance between their tones and the voice, to do so; and the voice does seem to have all the variations of note possessed by those instruments. Many creatures have no voice (as all the insanguineous, for instance, and some of the sanguineous, as fishes), which is very understandable, seeing that sound is a certain motion of the air; and with respect to those fishes which are found in the Achelous and said to speak, they produce sound by their gills, or other such part. But although the voice is a sound emanating from a living creature, it does not imply any kind of sound, or a sound produced by any kind of part; and as all sound is produced by the  conditions of something which percusses, something percussed, and a something, that is the air, in which percussion can be made, it might reasonably be assumed, that such creatures only as take in air can have a voice. Now, nature employs simultaneously the air respired for two functions, just as she employs the tongue for taste and for speech; and of these the former is necessary (and therefore imparted to most creatures), and the latter, as an organ for interpretation, is for their higher good; so too does she employ the breath both as necessary for tempering the heat within (as shall be explained elsewhere), and for the production of voice, which is for the welfare of the individual. The pharynx is the organ of respiration, for the sake of which is another part, the lung, and it is owing to this part that quadrupeds have more heat than other creatures.

It is the place about the heart which first needs respiration; and, therefore, it is necessary that the air, during inspiration, should pass inwards; and thus the percussion of the air respired by the living principle in those parts, against the so-called trachea, constitutes the voice. But every sound produced by an animal is not voice, as we have said (for it is possible to produce sound by the tongue, as in coughing), but in order to constitute the voice, there must be a percussing living force, and the sound produced must be expressive of something. The voice is, in fact, a  sound expressive of something—it is not, that is, as in coughing, a mere sound of the air inspired; and speech is the percussion, by the living principle, of the air in the trachea, against the trachea itself. As proof of which, we are unable to speak when holding the breath, that is, when we neither inspire nor expire; for the act of holding the breath sets in motion the air which is inspired. It is now manifest why fishes, having no pharynx, are without a voice; and they have no pharynx, because they neither admit the air nor breathe. It is foreign to our present purpose, however, to inquire into the cause of their having been thus constituted.


It is less easy to define smell and the odorous object, than the subjects which have just been treated of, as the nature of odour is not so clear to us as is that of either sound or colour; and the reason of this is, that our sense of smell is inaccurate, is less delicate, in fact, than it is in many animals. Thus, man has but a coarse smell, and is never sensible of any thing odorous without associating therewith an impression of something painful or grateful; and this seems to indicate an organ imperfectly constituted. It is probable that colours are perceived by creatures which have hard eyes in this same manner, and that shades of colour invariably make upon them an impression of something to be afraid of or otherwise. The human race is circumstanced in a like manner with respect to odours; and there seems to be an analogy between taste and kinds of savours, and smell and kinds of odours, but as taste is a kind of touch, and touch of all man's senses the most perfect, his taste is more delicate than his smell. With respect to other senses, man is far behind many animals, but he is especially  distinguished from them all by the accuracy of his Touch; and to this he is indebted for being of all the most intelligent. As proof of which, individuals of the human race are according to the constitution of this sense and nothing else, clever or dull for those with hard flesh are slow, and those, on the contrary, with soft flesh are quick of understanding.

As one savour is sweet and another bitter, so it is with odours; but some bodies impart an analogous savour and odour, impart, I mean, a sweet odour and a sweet savour, while other bodies give out their contraries. Some odours equally with savours are termed pungent, sour, and oily, but, as we have already explained, owing to their not being so distinguishable by us as savours, odours have derived their appellations from these, on account of the similarity of the objects from which they both proceed. Thus, the odour from saffron and honey is called sweet, that from thyme and other herbs of the kind pungent, and so for other bodies and odours.

There is a close analogy between the other senses and the hearing: for as it is sensible of the audible and the inaudible, so is vision of the visible and invisible, and smell of the odorous and the inodorous, and by inodorous is meant whatever is either altogether without odour, or has but a very faint odour; and a sense analogous to this is attached to the term insapid.  The smell is perceptive through a medium, such as air or water, for aquatic animals seem to be sensible of odour; and so, likewise, are sanguineous and insanguineous creatures, as well as those which wing the air. Thus, some of these are to be seen proceeding from a distance towards food, of which they have been made sensible by the odour emanating from it. And hence the difficulty of determining why, if other creatures are sensible of odours in a like manner, man alone can smell neither when expiring nor when holding his breath but, only when inspiring; and this whether the odorous object be at a distance from or close to him, or placed immediately within the nostrils. It is common, it is true, to all the sentient organs to be insensible to impressions when objects are placed immediately upon them; but it is peculiar to man (as may be proved experimentally), to be unable to perceive odours without inspiring. So that as insanguineous creatures do not breathe, they ought to have some other sense besides those spoken of, but yet this cannot be, since they do perceive odour; for the perception of odour, whether agreeable or disagreeable, is smell; and as these appear to be destroyed by the same powerful odours as those which destroy man (odours, for instance, from pitch, sulphur, and other like substances), we must conclude that they have smell, although they do not breathe.  The olfactory organ in man appears to differ from that in other animals as his eyes differ from those of creatures in which they are hard; for man's eyes are furnished with a rampart, and a kind of sheath in lids, without the elevation and drawing asunder of which he cannot see, while hard eyes, having no such provision, are instantly sensible of whatever may be present in the diaphanous medium. In accordance with this, the olfactory organ is, in such creatures, like the eye, uncovered; but, in such as breathe, it is furnished with a cover, which during inspiration is lifted up, as the veins and pores are then dilated. On which account, creatures which breathe cannot smell while in the water, as in order to smell they must inspire, and while in the water they cannot possibly inspire.

In fine, odour is derived from what is dry, as savour is from what is moist; and the olfactory organ, when in potentiality, is analogous to that from which odour is derived.


The sapid object is a kind of tangible object, and this is the reason why it does not require, in order to be perceived, any other medium than the body, for the Touch requires no other. The body in which is savour, is the gustable body, and the matter of savour is in fluid, and fluid is something tangible. Thus, were we in the water, and were any thing sweet cast into the water, we should be sensible of the sweetness, not through the water as a medium but, from its having been mixed with the water as with a potable fluid. Colour, however, is not thus made visible from having been mixed with anything, nor is it made visible by emanations; and as the medium, in the case of colours, plays no part and colour is the visible, so is savour the gustable. No object, however, without humidity can impart the sense of savour; and, therefore, every sapid object contains humidity, in an active or a potential state, as does salt; for salt is readily moistened and liquefied by contact with the tongue.

Now, vision is perceptive of the visible and the invisible (for darkness, although invisible, is still  judged of by vision), and a very bright light (which is also invisible, although in a manner different from darkness), and so hearing is equally perceptive of sound and silence, of which that is audible and this inaudible, as well as a very loud sound, just as vision is of a very bright light; for as a very low sound is, in a certain sense, inaudible, so is a very loud and crashing sound. On the other hand, the term invisible, used absolutely, is analogous to the term impossible upon other subjects, and which may be significant of something generated without parts or with parts ill formed for their office, as an animal without feet, or a fruit without a kernel. So, too, the taste in its turn is perceptive both of what is sapid and insapid; and the insapid implies whatever has a faint or nauseous savour, or a savour altogether perversive of taste. The potable and the impotable seem alike to be the origin of taste, for they both are sapid; but then the first has a nauseous savour, and is perversive of taste, while the last is genial to the sense; the potable is common, besides, to the touch and taste. Since whatever is sapid is humid, it follows that the organ of taste may neither be humid really, nor yet be incapable of becoming humid; for the taste suffers impression by the sapid body, in so far as it is sapid. It is, therefore, necessary that the sentient organ, if not moist, should, for its function, be capable of becoming so: and, as proof of this, the tongue, when  very dry or very moist, is not sensible of sapid impressions—as in the former instance, it is a tangible rather than a sapid impression which is made by a fluid when first tasted; and when very moist, it is sensible only of the fluid already present, just as it happens when, after tasting something pungent, we proceed to taste a different fluid. It is thus that all savours appear to the sick to be bitter, because the tongue, with which they taste, is charged with a moisture having that savour.

Kinds of savour are, like shades of colour, simple when in broad contrast—as the sweet and bitter with their sequences, of the former the oily and of the latter the brackish; and intermediate to these are the pungent, rough, astringent, and sour, which seem to include almost all the varieties of savour.

In fine, the sapid sense, when in potentiality, is such as is the sapid object; and the sapid object, when in reality, is productive, in the sense, of its own savour.


The same reasoning holds good for the tangible quality as for the Touch; for if the Touch be not a single but a manifold sense, it follows that tangible qualities must be manifold also. Now, it is difficult to determine whether the Touch is a manifold or a single sense, and difficult also to say what the organ may be which is percipient of tangible qualities; that is, whether or not it is the flesh, and that which, in other creatures, is analogous to flesh; but yet the flesh is only the medium, and the essential organ, therefore, must be something different from flesh, and situated internally.

Each sense seems to be perceptive of only one contrary, as Sight of white and black, Hearing of  acute and grave, and Taste of bitter and sweet; but several contraries belong to the sense of Touch, as hot and cold, wet and dry, hard and soft, with others. There is, it is true, a kind of solution for this difficulty, in that the other senses also admit of several contraries; as in the voice there are not only the acute and grave but also the strong and weak, the rough and smooth, with yet other contrasts; and there are many and varied shades of colour. Still it is not clear what that subjacent something is, which is to the tangible impression what the Hearing is to Sound.

Is then the sentient organ placed or not within the flesh, or is it the flesh itself which is immediately perceptive? It does not appear that any indication can be obtained upon this point from sensation being simultaneous with the tangible impression; for, situated as we are, were any one to extend a membranelike substance over his flesh, the party would be equally sensible when touched, and sensible at the moment of contact; and yet, clearly, the sentient organ cannot be in that membrane. It may be, however, that if the membrane were a congenital part of the body, sensation would pass through it more rapidly. Thus, this part of the body appears to be disposed towards us as air would be, had air been diffused around us; for it would seem to us as though by some one sense we perceive sound, colour, and  odour, and as though sight, hearing, and smell, are one and the same sense. But now, as the motions emanating from external objects are distinguishable by the medium through which they are conveyed, the sentient organs alluded to must manifestly be different also. With respect to the Touch, however, this is still obscure, for it is impossible that a living body should be constituted out of air or water, as it must have some solidity; and there remains only this conclusion, that it must be a mixture of earth, and such other particles as have affinity with flesh, and the analogue of flesh. Thus, the body has, of necessity, been adapted for being the medium for the tangible sense, through which the several tangible impressions are to be conveyed; and that the impressions are manifold is shewn in the tongue being perceptive of tangible as well as sapid qualities. We are sensible, in fact, by this organ of all tangible as well as sapid qualities; and were the rest of the flesh, like the tongue, sensible of savour, then "Taste" and "Touch" would seem to be one and the same sense; but now we perceive, since they are not convertible, that they must be distinct senses.

It may be a question whether, as all bodies have depth, that is the third magnitude, any two bodies, which have between them another body, can be in contact; for neither the humid nor the liquid is incorporeal, as each must, of necessity, be water or hold  water; and thus, it follows that, as the extreme parts of bodies in the water are not dry, the water, with which their extremities are covered, must be interposed between them. If this be true, then it is impossible that one body, when in the water, should be in immediate contact with another; and this holds good for bodies in the air; for the air is in the same relation to bodies in air which water is to bodies in water; but owing to our being in the air, the fact as readily escapes us, as it does aquatic animals, from their being in water, that water is in immediate contact with water. It may then be asked whether there is but one mode of impression for all the senses, or whether it is different for different senses, seeing that taste and touch are acted upon by contact, and the other senses from a distance? But yet this is a seeming difference only, for we perceive the hard and the soft, as we do the odorous, the sonorous, and the visible, through media; with this difference, that the former impressions are made by objects close to, and the latter by objects at a distance from us. On which account, as we perceive all things through a medium, the medium, in the case of bodies close to us, escapes our attention; but if, as we have already said, we could be sensible of all tangible impressions through a membraneous substance, without our being conscious of their having been so transmitted, we should then be situated as we now are, when in water or air;  for so situated, we seem to touch bodies directly, and to have no impression from them through a medium.

But tangible differ from visible and sonorous impressions, in that the latter are perceived by the medium acting in some way upon us, while the former are perceived, not by, but together with, the medium, like a man who is struck through his shield; —for it is not the shield which, having been struck, strikes him, but the shield and he are simultaneously struck together. To use a general expression, the flesh and the tongue seem to be in the same relation to the touch which air and water are to sight, hearing, and smell; —are disposed towards that organ, that is, as each of those elements is to each of those senses. When the sentient organ itself is touched, no sensation can there or then be produced, any more than a white object can be seen when placed immediately over the surface of the eye; and thus it is evident that the part perceptive of tangible impressions must be within. Thus, it should be with the touch, as with the other senses; and if objects, when placed upon an organ, are not perceived, but, when placed upon the flesh, they are perceived, we must conclude that the flesh is only the medium for tangible impressions.

The distinctions of the body, as body, are tangible distinctions, and by these I mean distinctions such as distinguish the elements, as hot, cold, dry and moist, upon which we have heretofore spoken in our treatise  upon the Elements. The organ which perceives those distinctions is that of Touch; and the part in which resides, primarily, the so-called sense of Touch is, in potentiality, what tangible impressions are in reality; for all sensation is a kind of impression. So that whatever, by its agency, makes something else to be as itself, can do so only from that something being already, as itself, in potentiality. Hence, we are not sensible of hot and cold, hard and soft, when manifested in the same degree as in ourselves, but perceive them only when in excess, as if the sensibility were some kind of mean between the contraries of sentient impressions, and able, as such, to judge of sentient perceptions. The mean, in fact, is critical—for it is either of the extremes in its relation to the other; and as that which is to perceive white and black may be neither one nor the other actually, and yet both potentially, so it is with the other senses, and with touch, which may be neither hot nor cold.

As vision was said to be, in some sense, perceptive of the visible and the invisible, and the other senses equally of their opposites, so Touch may be said to be perceptive of the tangible and the intangible; and by intangible is meant as well what differs but slightly from what is tangible, as air for instance, as what is in such excess as to be destructive of all sensation.

We have thus then spoken, although but superficially, upon each of the senses.


It must be admitted, for the senses in general, that each one is receptive of the perceptible forms of things without the matter, as wax takes the impress from a seal-ring, without the iron or gold of which the ring is made; —takes the device, that is, without the metal on which the device is inscribed. In like manner, the sense is impressed by each object having colour, or savour, or sound; not, however, after the appellation of the object but, according as it is of a certain quality, and in a given relation to the sense. It is the primal organ in which this faculty exists; and it is identical with the object perceived, although different from it in mode of being; for, otherwise, the percipient would be some kind of magnitude. But it cannot belong either to that percipient or to sensation to be magnitude, as they are rather a relation to, and a faculty for the perception of the qualities of each object. Thus, it is, from these reasons, made manifest why sentient impressions in excess destroy the sentient organs; for if the motion of the impression be stronger than that of the organ, then the relation  which constitutes sensation is dissolved, as harmony and tone become discordant, when the chords are struck too forcibly.

But why do not plants feel, seeing that they also possess a living part, and are impressionable by tangible qualities? And that they are so impressionable is shewn in their being both cooled and heated; but the cause is that they have not that mediate faculty, nor any such principle as admits of their receiving only the forms of things; that along with forms they are affected by the matter also.

It may be questioned whether impressions can be made by odour upon what may be without smell, or by colour upon what may be without vision, and so for other qualities and senses. But if that which is smelt be odour, then odour, if it produce anything, must produce smell, and thus nothing without smell can be affected by odour, and the same holds good for the other senses; neither can beings which are sentient be affected, save in so far as they are sentient. All which is made evident in that neither light nor darkness, sound nor odour, can act upon bodies, although that which is present with them may, as air with thunder splits wood. But yet tangible and sapid qualities do act upon bodies; for, otherwise, by what could inanimate things be acted upon and changed? Shall it then be said that those other qualities also act upon bodies? But all bodies  are not impressionable by odour and sound, and those which are so are indefinite and mobile, such as is the air; for the air gives out odour, as if it had been subject to impression. What then is smell but impression of some kind? But smelling is a sentient perception; and the air having been impressed by odour, becomes quickly sensible to us.


We may be satisfied, from the observations which follow, that there is no sense besides the five—besides, that is, Sight, Hearing, Smell, Taste, and Touch; for if Touch be the sense for every impression of which we are sensible, and if we have this sense, then, as all the conditions of whatever is tangible, in so far as tangible, are made perceptible to us by the Touch, it follows that, if any sensation be wanting, some sentient organ must be wanting to us also. Now, all the bodies which are perceived by touching are made sensible to us by the Touch which has been allotted to us; and all those which are perceived, not by touching but, through media, are made sensible to us by simple bodies—that is, by air and water. We are so constituted, in fact, that, if several objects, differing generically from one another, could be perceived through one medium, an individual, having a sentient organ such as that medium, would,  necessarily, be sensible of impressions through both media—as if the sentient organ should be of air, then, as air is the medium for sound and colour, the individual would be sensible of both impressions through the same organ. Should there, however, be more than one medium for the transmission of the same impression, as air as well as water (since both are diaphanous,) serves for the transmission of colour, then an individual, having an organ constituted of either of those elements, would perceive impressions transmitted through them both. The sentient organs, however, are constituted of those two simple bodies, air and water, exclusively—for the pupil is of water, the hearing of air, and the smell either of one or other; but fire forms no part of any organ, or rather it is an element common to all, as there is nothing sentient without heat; and earth either does not enter at all into any sentient part, or it has been in some especial and peculiar manner combined with the Touch. Thus, there can remain only this conclusion, that, were there no air or water, there could be no sentient organ; and organs so constituted are actually possessed by animals now living. All the senses, in fact, are possessed by animals which are neither imperfect nor mutilated; for the mole appears to have eyes beneath its skin. So that, unless there is some kind of body hitherto unknown and some kind of impression unsuited to bodies here on earth, it may be affirmed  that no sense can be wanting to us. But neither is it possible that there should be any special organ for the perception of common properties, (such as motion, rest, magnitude, form, number and unity), of which we are made sensible, by each special sense, accidentally; for we perceive all such by motion as we do magnitude, and as we do form, as form is a kind of magnitude; the state of rest we are sensible of by the absence of motion, and number we perceive by the want of continuity and by particular senses, for each sense is perceptive of unity. So that, evidently, there cannot be a peculiar sense for the perception of any one of those properties, as motion, for instance; with respect to which we shall be ever situated as we now are, when, by sight, we judge of something sweet. And this we are able to do from our happening to possess a sense which is perceptive of double impressions, and by the way in which those impressions coincide, we recognise what the thing is; were this not the case, then, in no wise, except by chance, could we perceive that the thing was sweet, any more than we could tell that an individual is the son of Cleon, not because he is really so, but because he is fair; and fairness is an accident pertaining to the son of Cleon. And yet we have a common sense for the perception of common properties and that not casually, although it is not a peculiar sense; for, were it so, then in no otherwise could we perceive those  properties than, as has just been said, we see that an individual is the son of Cleon. The senses, however, do perceive, casually, the special qualities of each other; but then they do so, not as distinct senses but, as becoming one sense, as when double impressions may be made simultaneously upon the same organ, as by bile, which is bitter and yellow. But as it belongs not to either sense to say that both qualities belong to one substance, we are exposed to error, and led to think that if a fluid be yellow it must be bile.

Should any one inquire why we have been furnished with several senses in place of having only one, it might be answered, " that we have so been constituted in order that the sequences and common properties of bodies, as motion, magnitude, and number, may the less readily escape our notice." If vision, in fact, were our only sense and it perceptive only of whiteness, then all other qualities would more readily escape our notice and seem to be identical, on account of colour and magnitude being in an invariable sequence to one another. But as here common properties are manifested in different bodies, it is evident that each of those properties (colour and magnitude) must also be different.


Since we are sensible that we see and hear, we cannot but be sensible that we see by sight or by some other sense; but, if we see by some other sense, then it will be perceptive of sight and colour, the subject of sight; and thus there will be either two senses for the same office, or the sight itself will be the percipient. If, besides, there is some other than the visual sense for sight, we shall have to admit an infinite series of perceptions, or else this other sense, whatever it may be, will be the visual percipient; and this might as well have been conceded to the first sense. But here there is a difficulty—if to perceive by sight is seeing, and if that which is seen is colour or something having colour, then, if any sense is to see that which sees, that sense must first have colour. It is then manifest that perception by sight is not a single perception; for even when we may not see, it is still by sight that we judge both of darkness and light, although not in the same manner. That, moreover, which sees, must have been already imbued with colour, since each sentient organ must be receptive of the object of  perception without its matter ; and this accounts for impressions and images being still present in the sentient organs, after objects have been withdrawn.

The action of the object of perception is one and the same with that of the sense, although they differ in mode of being—I mean, for example, sound in action and hearing in action ; for it may be that an individual, endowed with hearing, does not hear, as that a sonorous body does not give out sound. But when an individual, capable of hearing, listens, and when that which is sonorous gives out sound, then hearing in action coincides with sound in action, and the one may strictly be termed hearing, the other sound. If motion, production, and impression, are in the product, it follows that sound and hearing, in an active state, must pre-exist in hearing in a potential state; for the action of the creative and the motive exists, naturally, in that which is to be acted upon. It is, therefore, no way necessary that the motor should be itself in motion. The action, then, of the sonorous body is sound or sounding, that of the auditory sense is hearing or audition; for hearing is double as sound is double, and the same applies to other senses and perceptions. Since production and impression are, not in that which acts but, in that which is impressed, so the action of the object of perception and the sensibility is in the sentient being. But, while for some senses these two states have  been specially distinguished by names, as sound and hearing, there are others for which one or other state is without appellation—the action of vision, for instance, is called sight, but the action of colour is unnamed; the action of the sapid sense is called taste, while that of savour is without appellation.

Since the action of the object of perception and that of the sentient being is one and the same, although different in mode of acting, it follows that hearing and sound, in this sense, must together be lost, or together be preserved; and this is true of taste and savour, and other senses and functions; but yet it does not hold good of those relations in potentiality.

The earlier physiologists have expressed themselves ill upon the subject, as they thought that there can be neither black nor white without sight, nor savour without Taste. And yet what they said was in part right and in part wrong; for as senses and sentient impressions have a twofold acceptation, according to their state of potentiality or activity, so what was advanced by them may be applicable to the one state, and inapplicable to the other. The fact is, those writers reasoned absolutely upon conditions, which do not admit of being so dealt with. If a voice of any kind is harmony, and if voice and hearing are, in one sense, the same, and, in another sense, not the same, then, as harmony is proportion, it follows that hearing must be proportion also. And hence it comes  that every sound in excess, whether acute or grave, perverts the hearing, as every savour in excess does the taste; and every colour over-bright or dark dulls the sight, as every odour excessively pungent, whether grateful or offensive, does the smell, as if shewing that sensibility is a kind of proportion. Thus, qualities, as acid or sweet or saline, are agreeable whenever they are reduced, pure and unmixed, to a due proportion; for it is this only which renders them grateful. To speak generally, harmony is a combination of tones rather than the acute or the grave singly, as for the Touch, the warmed or cooled is genial, rather than the hot or cold, simply; for, as sensibility is proportion, so qualities, in excess, pain or pervert the senses.

Each sense is perceptive of its own appointed subjects, is innate in its own organ, as a special organ, and judges of the distinctions of qualities, as sight judges of white and black; taste of bitter and sweet, and so as to other senses and qualities. But since we judge of white, sweet, and each other quality by its relation to each sense, by what do we perceive that qualities differ? Now, it is evident that it must be by some sense, as the impressions are all sentient; and equally so that the flesh cannot be that final organism, as in order to judge of qualities it must, of necessity, first touch bodies. Neither is it admissible that, by different senses, we judge sweet  to be different from white, as both qualities must be apparent to some single faculty; for, otherwise, it would be as if I should perceive one quality and you perceive another, and thus make it evident that they are different from one another. But it is here required that the same individual should perceive that they are different, for the sweet is different from the white, and what he perceives that he says; and thus, what he says that he thinks and perceives. It is then evident that we cannot, by different senses, judge of different qualities, as also, from what follows, that we cannot judge of them in a separate portion of time. Neither can an opinion be in a separate portion of time; for just as it is the same individual who says that good is other than bad, so when he says that the one is different from the other, he implies that the other is equally so, and does not employ the term when loosely—he does not use it, I mean, in the sense of now, in the phrase, "now I say that the object is different," without implying that it is different now. But, here, it is the same individual who employs the term now, and says that objects are different now and because now; for the impressions are coincident, as they are inseparable, and as the time is indivisible. It cannot, however, be, that the same individual, in so far as indivisible, should be subject to contrary impulses in time which is indivisible; yet if sweetness move sensation or thought in one way, bitterness  must move them in an opposite, and whiteness in some other direction. Can, then, that which judges be, numerically, indivisible and inseparable, yet separable in its mode of being? If so, then, in some way, as divisible, it may perceive divisible, and, in some way, as indivisible, it may perceive indivisible qualities; for in its mode of being it is separable, but, locally and numerically, it is inseparable. But is not this impossible? The same may, in potentiality, be indivisible and divisible and be the contraries; but not so in mode of being, as it is divisible in action, and cannot possibly be at once white and black, nor be simultaneously impressed by the forms of those colours, provided sensation and thought are such as we have said they are. But it is with this, as with that which some call a point, and which, in so far as it is one or dual, is indivisible or divisible. Thus, in so far as that which judges is one, it is indivisible, and its perceptions are simultaneous; and in so far as it is divisible, it employs the same point twice, simultaneously. In so far, then, as it employs the boundary as two, it judges of two things by it and perceives that they are distinct, as the boundaries of the line are distinct; but in so far as it is one, it judges by one act, and judges simultaneously.

Let what has been said then suffice for the definition of that principle, by which we maintain that an animal is made a sentient being.


As writers, for the most part, define Vital Principle by two different faculties, by locomotion and thought, judgment and sensibility, it would seem as though thought and reflexion are by them considered to be some kind of sensation; for, in both cases, the Vital Principle both discerns and recognises something. Thus, the ancients affirm that reflexion is identical with feeling; and Empedocles has said, "man's intelligence is enlarged by what is present," and, elsewhere, "hence, man derives his power of reflecting upon different subjects;" so Homer's words, "such is the mind" do but express the same idea. All these writers assume, in fact, that thinking, like feeling, is corporeal, and that Like is perceived and comprehended by Like, as was explained in our opening chapters. But yet it was incumbent upon them to have spoken, at the same time, upon the liability to error through the senses; for this belongs, more peculiarly, to animals, and Vital Principle remains subject to it during the greater portion of existence. On which account, either all appearances are, as some of  those writers maintain, necessarily, true, or else error is caused by contact of the unlike, which is the opposite of the opinion, that like is recognised by like; and the error from contraries seems to be identical with the knowledge of contraries. It is manifest that feeling is not identical with reflexion; for, while the former belongs to all creatures, the latter has been imparted only to a few. Neither is thinking, that faculty to which belongs the sense of right and wrong, (the right comprehending judgment, knowledge, and sound opinion, the wrong comprehending their contraries,) to be confounded with feeling—for sensation, being derived from particulars, is ever true, and belongs to all animals; but the judgment may be wrong, and is imparted only to such as have reason. Imagination, in fact, is neither sensation nor judgment, and yet it is not called up without sensation, just as, without sensation, there can be no conception; but it is manifest that imagination is not conception. Imagination depends, in fact, but upon ourselves, as we can, at will, call it up (since it is in our own power to place images before the eyes, as do they who, for mnemonic aids, by laying down objects, form symbols); but to form an opinion does not depend upon ourselves, and then every opinion is, of necessity, either true or false. Whenever, besides, we may have an opinion upon any terrible and fearful incident, we are straightway affected as if it were a reality, just as  We are when we think upon any desperate deed; but, under imagination, we become simple spectators, as it were, of a pictorial representation of terrible or daring achievements. There are, in conception itself, the distinctions of knowledge, opinion, reflexion, and their contraries, of which we shall speak elsewhere. With respect to thinking, since it is different from feeling, and feeling seems, in part, to be imagination and, in part, conception, let us here define imagination, and then proceed to the consideration of the other faculty.

If imagination be a faculty by which we say that an image of some kind, and that not merely in the sense of a metaphor, is called up within us, then it is to be ranged among those faculties or powers, such as feeling, opinion, knowledge, mind, by which we form judgments and determine what may be true or false.

It is clear from what follows, that imagination is not sensation ; for sensation is either a faculty or an act, such as sight, and seeing, but an image is sometimes apparent to us without either faculty or act, as phantoms in dreams for instance; and then sensation is ever present, which is not the case with the imagination. If, moreover, imagination were in act identical with sensation, we should have to admit that it must belong to all irrational creatures, but this does not seem to be the case with the antbee, or worm; and then sensations are always true, but imaginings are for the most part false. Hence, we do not say, when accurately  examining any object, that we imagine to be so or so, a man for instance, but we so express ourselves rather when we do not clearly perceive what the object is, and when the perception may be true or false; when, to use a former expression, the object appears to us as landscapes do to the purblind.

Neither can imagination be regarded as one of those faculties, such as knowledge and mind, which are always true, for it admits of being false as well; and it remains for us to consider whether it is opinion, since opinion may be both true and false. But belief follows upon opinion, (as it is not admissible that an individual should not believe in that upon which he has an opinion,) and belief belongs to no irrational creature although imagination is imparted to many. Belief, besides, is an attendant upon every opinion, as persuasion is upon belief, and reason alone can persuade ; but although imagination belongs to some irrational creatures, reason has been given to none. It is manifest, then, that imagination can neither be opinion with or through sensation, nor a combination of opinion with sensation; and for the same reasons evident, that opinion is from nothing else but that from which sensation is derived. By which I mean, if imagination be the combination of an opinion of whiteness and a sensation of whiteness, and not of an opinion of goodness with a sensation of whiteness, then to imagine is to think upon what has been sensually  perceived, and that not accidentally. But there are appearances which are fallacious, although our conception of them at the time may be true, as the sun, for instance, appears to be a foot in diameter, and yet we are satisfied that it is larger than the earth; and in such a case it happens either that the true opinion of the sun's dimension must have been cast aside, or else, while the sun remains as it was and the true opinion has neither been forgotten nor changed, that the opinion is at once both true and false. But the opinion is simply false when it escapes us that the thing seen is altered. It is evident, then, that imagination can neither be any one, nor be derived from any one of those faculties.

Since one object having been set in motion can communicate motion to another, and since imagination seems to be a kind of motion, and never to be produced without sensation, or in other than sentient creatures, or without the objects of sentient perception, and since, on the other hand, motion can be produced by the act of sensation, and this motion must of necessity be equal to the impression, it may be admitted that the motion of imagination can neither be produced without sensation, nor in other than sentient beings; that beings endowed with it act and are acted upon in many ways, and that its manifestations are both true and false. This latter alternative happens thus: the sensation which is derived from the objects peculiar  to each sense is true, or it involves the smallest amount of error; but when, in the second place, such objects are perceived in their accidents, there is room for fallacy; when for instance, something is said to be white, there is no fallacy, but when that object is particularised and said to be this or that, the perception may be fallacious. There is, in the third place, liability to error in our perception of common properties, and sequences in the accidents referrible to particular bodies—accidents, I mean, such as motion and magnitude, which are referrible to all bodies, and from which there is peculiar liability to error through the senses. But the motion produced by the act of sensation will differ from the sensation derived from these three modes of sensation—the first, while sensation is yet present, must be true; but the others, whether sensation be present or not, may be fallacious, and more especially, when the objects causative of sensation may have been withdrawn. If, then, imagination alone fulfil all the conditions indicated, and if it be all that has been said, it may be defined as motion produced by sensation in action. And since vision is a sense above all others, imagination has derived its appellation from light, because without light there is no vision; and owing to its being an abiding faculty and like sensations, animals perform many of their actions through it. Some animals are so influenced from being irrational; and others, as man, from having  their understanding eclipsed, at times, by passion, disorder, or sleep.

Let this much, however, suffice for the inquiry into imagination, for shewing what it is, and for what purposes it has been imparted.


With respect to the part of Vital Principle by which it both knows and reflects, whether that part be separate, or separate, not substantively but, in an abstract sense only, let us now consider in what it is distinguished from other parts, and how thinking is at any time exercised. If thinking be such as is feeling, then it may be some kind of impression by the subject of thought, or other analogous agency. But then that which thinks must be impassive, receptive of the form of objects, and, in potentiality, the same as the object, without actually being so. The mind, in fine, must be related to subjects of thought as the sensibility is to objects of perception. It is, then, necessary since the mind thinks upon all subjects, that it should be homogeneous, in order, as Anaxagoras expresses himself, that it should domine, that is, recognise things; and as whatever is foreign to it precludes and eclipses its inward light, so it can have no other nature than that of potentiality. Thus, the so-called mind of Vital Principle (and by mind I mean that part by which Vital Principle judges and compares), is not actually any one of the subjects of thought before  thinking upon it. It is very improbable, therefore, that the mind should have been commingled with the body; for were this the case, it would be a quality of some kind, as hot or cold, or it would have some kind of organ as there is for the sensibility, but no such organ is to be found. It is well said by some that Vital Principle is the place of forms, only this is to be understood of Vital Principle, not as a whole but as a cogitative faculty, and of forms, not in reality but, in potentiality.

It is manifest, from the nature of the sentient organs and sensation, that the quiescent state of the sentient is not the same as that of the cogitative part. For the sensibility is unable to distinguish impressions in excess, as a sound amid loud sounds, or a colour or odour among brilliant colours or pungent odours, but the mind, on the contrary, when thinking intensely upon any subject, can still think and with increased rather than diminished intensity upon the subordinate details; the sensibility, besides, cannot be without a body, but the mind is separable. When thus situated, the mind can become each of the subjects of thought, as an individual is said to be learned actually (and this may be said when he is able at will to employ his learning,) because he is at the same time equally learned in potentiality, although not as he was before he had learned or invented something; for when so learned he is able to reflect upon his learning.

There is a distinction between positive magnitude and ideal magnitude, water and ideal water, and so between many but yet not all substances, as with some the two states are identical, but the mind judges of flesh and ideal flesh either by some different faculty or by being itself differently disposed; for flesh cannot be without matter, but, as is a snub nose, it is something in something. Now, it is by the sensibility that we judge of hot and cold and other properties of which flesh is the standard; but it is either by some distinct faculty or as a curved is to an extended line, that we judge of ideal flesh. Straightness, on the other hand, as well as the snub nose we place among abstractions, for each is associated with continuity; but the difference, if there be a difference, between positive straightness and ideal straightness, the mind judges of by some other, perhaps a dual faculty; by some other faculty, at least, or by being itself differently disposed. To use a general expression, as are things abstracted from matter so are subjects of thought with respect to the mind.

It is difficult to determine how the mind, if it be as Anaxagoras supposes, homogeneous, impassive and without any thing in common with aught else, is to think, if thinking be some kind of impression; for it is only in so far as there is something in common between two substances, that the one seems to act and the other to be acted upon. And there is  the same difficulty if the mind itself is intelligible; for it will be present in other things, unless it is itself, intelligible in some other way than they are, and unless the subject of thought is some one specific subject; or else the mind will be some kind of combination, and this reduces thought to the nature of other things. But to suffer impression according to some common relation implies, as has been just explained, that the mind, in potentiality, is as the subjects thought upon, and yet that, in reality, it is no one of them before thinking upon it; and thus the mind is to be regarded as a tablet on which nothing may have been actually inscribed. The mind is a subject of thought to itself as is any other topic, since that which thinks and the subject of thought are among immaterialities; for speculative knowledge is the same as the subject which is so known. But we have to consider why the mind is not always thinking, as each subject of thought, in potentiality, is among materialities; so that the mind will not be present in any one of them (for the mind is the immaterial faculty which judges of them), although each of them will be subject to the mind.


Since, throughout all nature, there is a matter for each genus of entities (that which all belonging to that genus are in potentiality), and a something which is causative and constitutive from its making things what they are, as art impresses its forms upon matter, so those same distinctions must, of necessity, co-exist in the vital principle. Such also is the mind, from its faculty, on the one hand, of becoming all things, and, on the other, of creating all things, as if it were a virtuality like light; for light, in a certain sense, makes colours, being in potentiality, to become colours in reality; and the mind here meant is separate, impassive and homogeneous, being essentially an energizing influence.

That which acts is ever, in fact, more influential than that which is acted upon, as the causative principle is than the matter. Now, knowledge in activity is identical with the subject; but knowledge in potentiality pre-exists in the individual; and yet, strictly  speaking, it does not pre-exist, as that cannot be said to pre-exist which sometimes is, and sometimes is not reflected on. But that alone, whatever it be, which thinks, is separate from all else, immortal and eternal; and, because it is impassive, we derive from it no memory. But the impressionable mind, on the contrary, is perishable; and without it there can be no cogitation.

Whenever cogitation is employed upon what may be indivisible it is not subject to error, but when engaged upon topics which involve both error and truth, there is a simultaneous combination of thoughts, whereby they are, so to say, individualized; in the way that Empedocles expressed himself, "Now the heads of many creatures budded forth without necks, and then, heads and necks were by affinity made one." It is thus that thoughts, however disconnected, as the incommensurable and the diameter, are by the intelligence joined together. If the question relate to things past or future, the mind, thinking upon time besides, adds it to the other conditions; for error lies ever in the combination, as when the white is said not to be white, the error is in the addition of the negative. Now, it is always in our power to speak of things individually; but then, it is not only true or false that Clem is fair, but equally so that he ever was or ever will be fair. It is the mind which individualizes each subject. But since the indivisible is in the twofold state either of potentiality or  actuality, there is nothing to preclude the mind when thinking upon extension, from thinking upon it as indivisible, for it is indivisible, actually, and in time which is indivisible; as time, like extension, is both divisible and indivisible. It may not then be said that the mind thinks upon any subject in each half; for extension exists only in potentiality, unless it have been divided. But the mind, when thinking upon each of the halves separately, divides the time simultaneously, and then time becomes such as the two extensions; and if the mind make a whole of the two halves, it does the same with time in its relation to them. The mind, however, thinks upon the indivisible as species and not as quantity, in an indivisible portion of time and by an indivisible part of Vital Principle; and this neither by accident, nor in so far as the subjects thought upon, or the part by which, or the time in which, it thinks, are divisible, but as they are indivisible. There is, in fact, in such cases a something indivisible, although it may not be separate, which makes time and extension to be one; and which holds good for all continuity, whether of time or extension. Now, the point and every analogous division, and whatever is as the point indivisible, are made known as being privation of something. The reasoning upon other subjects is like this, for were it asked how the mind is to recognise bad or black, it may be answered, that it recognises them in some way by their contraries;  but that which recognises them must, in potentiality, be the thing recognised, and be present also in it. If to any one of the senses there is no contrary, then that sense recognises itself, is in activity and separate from all else. An affirmation, like a negation, is something in relation to something, and is always either true or false; but not so with the mind, as it is true when it judges of any thing after its essence, and may not be true when it judges of something in its relation to something else. Thus, the visual perception of any particular object is true, but whether a something white which is seen be or be not a man is not invariably true; and this holds good for abstractions.

Knowledge is, when active, identical with that which is known; but knowledge, in potentiality, pre-exists in the individual, and yet, strictly speaking, it does not pre-exist, as all products are from a being in reality. Now, it is the object of perception, which appears, by its agency, to create sensation from the sensibility which is in potentiality; for it suffers neither impression nor change. So that this is a different kind of motion; for motion was said to be the act of something incomplete; but an act in an absolute sense is different, as it is the act of something complete. Thus, a simple sensation is like to a simple affirmation or a single idea; and as the impression may be grateful or painful, it is, as it were, affirmative or negative, and it bids  to flee from or pursue after something; and perceptions of pain and pleasure emanate from the sentient medium in its relation to good or evil, in so far as things may be one or other. So actual flight from something is identical with actual appetite, as the fugitive impulse does not differ from the appetitive stimulus, for they differ neither from one another nor from the sentient medium; and yet they do differ in mode of being. Images belong, naturally, to the thinking, as sensations do to the sentient principle; and as it may affirm or deny that anything is good or bad, it bids to flee from or pursue after it. The Vital Principle, therefore, never thinks without an image; as the air has made the pupil what it is, the pupil something else, and so with the hearing; but the last term is one, as the mean, to which belong several modes of being, is one.

It has already been said by what faculty the mind discerns that sweet differs from hot, but yet it may be spoken of again here. It is then an unit of some kind; and an unit in the sense of a limit, for it is as an unit and a limit in the relation, considered analogically and numerically, which the unit bears to the limit. What matters it, besides, whether our doubt is as to how the faculty judges of things, generically, the same, or opposite, as white and black ?

Let A = white be in relation to B = black, and let C be to D as A is to B, and so reciprocally; if CD be  properties of some one body they will be as the properties AB, and the body will be one and the same with the other, although not the same in the mode of being; and the same reasoning will hold good, of course, though A be = sweet and B = white. Thus, the cogitative faculty dwells upon ideas in images, and by images, independently of sensation, it in some way determines what ought to be pursued after or fled from; but, when acted upon by images, it is moved to think, and, perceiving the beacon to be on fire and moving, it comprehends, by that common property (motion), that an enemy is at hand. Sometimes, too, by images or thoughts present in Vital Principle, that faculty, as if seeing, calculates and orders things future in their relation to things present; and when it suggests that something is grateful or hurtful, it bids to pursue after or flee from it, as its biddings always tend to action. And with respect to all which pertains to inaction, the true and the false are in the same genus with the good and bad; but with this difference, that the former have an absolute, and the latter only a relative signification. The mind dwells upon abstractions, so termed, as it thinks upon a snub nose: in so far as it is a nose of that character it cannot be thought upon abstractedly, but in so far as it is concave the mind can, by thinking intensely upon the form, realise to itself the nose without the flesh in which the form is embodied. Thus, too, the mind  thinks upon mathematical questions as abstractions, although they are not really so, when they are thought upon.

In fine, the mind when thinking, is, in act, the thing thought upon. It shall hereafter be considered whether or not it can be admitted that the mind, without being itself apart from magnitude, can comprehend abstractions.

Having thus summarily recounted whatever has been said upon the Vital Principle, let us repeat that it is, in some sense, all things which are; for things are the subjects either of sentient perception or of thought, and knowledge is, in some sense, things known, as sensation is things sensually perceived. But let us inquire how this is to be understood—Knowledge, then, like sensation is divided, when in potentiality, into things in potentiality, when in reality, into things in reality; and the sentient and the cogitative faculties of Vital Principle are, when in potentiality, identical with thoughts and objects of perception, in potentiality. But the question here must necessarily refer either to things or the forms of things; but the things themselves they cannot be, as it is not a stone but the form of a stone which is in the Vital Principle. Thus, the Vital Principle is, as it were, a hand, for as a hand is the instrument of instruments, so the mind is the form of forms, and sensation the form of things sensually perceived. Since there is, seemingly, nothing  separate from perceptible magnitude, it must be admitted that all subjects of cogitation are in perceptible forms, as well those termed abstractions as those which relate to the conditions and changes of the objects of perception. And, therefore, if a being were without sentient perception, he could neither learn nor understand; as for reflexion the individual must be able to call up an image of some sort, and images are kinds of sensations, excepting that they are immaterial. Imagination, on the other hand, is something different from affirmation and negation, for the true or the false is but a complication of thoughts. But by what are primal thoughts to be distinguished from such as are derived from images? Other thoughts, however, are not images, and yet without images they could not be produced.  THIS and the two following chapters are upon the parts or powers rather, which give to animals locomotion; but, as the nervous even the muscular system had not then been made out, the text is encumbered, occasionally, as might be expected, with speculations which may now seem idle, and distinctions which are almost futile. Aristotle[1] makes “animals to move and be moved for the sake of something, which is the limit of all their movements; and the moving powers of an animal are, perceptibly, he adds, thought and imagination, election, will and desire, which are all referrible to mind and appetite, εἰς νοῦν καὶ ὄρεξιν. Thus, as imagination and perception are alike able to direct an animal, they are in one and the same relation to the mind. The argument, in fact, dwells upon the motive as well as the object for progression, without a word concerning the agency by which it is to be effected, as if the muscular power of the body were unknown, or

SINCE the Vital Principle of animals has been defined by the two faculties of judgment (which is the office of thought with sentient perception), and of locomotion, let us now, having dwelt sufficiently upon sensation and mind, proceed to consider, with respect to the motor power, what part of the Vital Principle it may be. Let us consider, that is, whether it is a part of Vital Principle and separate from it, substantively or abstractedly, or whether it is Vital Principle as a whole; and if it be a part, whether it is something peculiar and exclusive of those usually attributed to Vital Principle, and which have been alluded to, or whether it is to be considered as one of them.

But a difficulty at once presents itself, both in  determining the sense in which we are to speak of the parts of Vital Principle, and in settling how many of them there may be. In one point of view, in fact, the parts appear to be infinite in number and to comprise, not only those which some speak of as the reasoning, passionate and appetitive, and others as the rational and the irrational, but other parts also, which by the distinctions employed in those classifications, are brought into notice, and are more broadly distinguished from one another than are any of those to which we have alluded. Those other parts are the nutritive, which belongs to all plants and animals, and the sentient, which cannot readily be placed among either rational or irrational parts; there is the imaginative, besides, which differs in mode of being from all the others, and yet it would be difficult to determine, amid the several parts of Vital Principle, with which of them it is identical, or from which it differs. Besides these, there is the appetitive part, which, whether considered abstractedly or functionally, would seem to differ from all others, and yet it would be absurd to separate it from them; for volition is present in the rational, as decire and passion are in the irrational part, and if the Vital Principle be made up of these three, appetite must be present in each of them.

But, to resume the more especial topic of this chapter, what is that, let us ask, which confers upon  an animal locomotive power? Now, it may be supposed that the generative and the nutritive functions, which are innate in all living beings, originate the motion concerned in the processes of growth and decay, which equally belong to them all; and with respect to breathing and expiration, sleep and watching, which are subjects of much difficulty, we shall enter upon the consideration of them hereafter. Let us, however, consider what confers upon an animal the power of progression.

Now, it clearly is not the nutritive faculty—for the movement of progression is ever for some end, and is associated either with imagination or appetite; and then no being moves unless urged to it by desire or fear, excepting, indeed, there be impulse from without; plants, besides, were nutrition the cause, should be locomotive, and possess some organ to fit them for that kind of movement.

Neither can it be the sentient faculty—for there are many creatures which are sentient, and yet stationary throughout their existence; and if nature do nothing in vain, and never, except in the case of beings dwarfed or deformed, omits anything necessary to existence, the creatures alluded to are perfect creatures; and as proof of this they are reproductive, are capable of development and subject to decay, so that they also ought to have organs to fit them for progression.  Neither can the rational faculty or the so-called mind be the motor power, for the speculative intellect never thinks upon what is to be done, or suggests aught concerning what should be fled from or pursued after; but this motion is the act of one fleeing from or pursuing after something. Nor does that faculty, even when reflecting upon any such object, at once bid to flee from or to follow after it, as it often dwells upon something terrible, or agreeable, without suggesting alarm, although the heart may be set in motion or some other part of the impression be agreeable. Add to this, that although the mind may bid, and the reason suggest that something should be fled from or pursued after, the individual does not necessarily move, but acts as does an intemperate person, according to the dictates of passion. It is thus, occasionally, we see that a physician, although versed in medical science, does not cure, as if there were something other than the science which had the power of acting according to the precepts of the science.

It may be affirmed that the appetite cannot be the positive cause of this motion; for the temperate, even while desiring and yearning after something, do not act in order to secure that for which they feel appetite, but follow their understanding.


THOSE two faculties, the appetite and the mind, appear to be the motor principles in animals—the mind, if the imagination might be set down as being a kind of thought; for many against knowledge follow their imaginings, and other animals are moved neither by thought nor calculation, but by imagination. Thus, those two faculties, mind and appetite, are locomotive powers; but, then, it is mind in the sense of a calculating and a practical faculty, and which differs from the speculative mind by the object to which it tends.  Now, every appetite tends to some object, for the appetite, which is the beginning of the practical mind, has ever some object in view, and that object is the beginning of the action. So that these two, appetite and practical thought, may reasonably be regarded as motor powers—for the object longed for impels to move, and then, through it, the practical intelligence impels, because its origin is the object longed for; and when imagination may incite to move, it never does set in motion without appetite. Thus, it is the object longed for alone which produces motion; for if there were two motives, mind and appetite, they would produce motion according to some common formula. But as the case is, the mind does not appear to produce motion without appetite, for volition is appetite; and even when a creature may move by calculation, it still moves by volition; the appetite, on the contrary, impels to move against calculation, for desire is a kind of appetite.

The mind then is always right; but appetite as well as imagination may be right and may be wrong. It is, therefore, the object desired which always excites to move, but then that object is a good or an apparent good; not however, a good in every sense, but a practical good, and a practical good admits of being otherwise than good.

It is manifest then, that it is that faculty of Vital Principle, the so-called appetite which excites to  move. But when Vital Principle is divided into parts, and parts are distinguished by their faculties, very many are made apparent, as the nutritive, the sentient, the cogitative, the deliberative, and the appetitive, and these differ from one another more than do the desiring and the passionate.

The appetites admit of being opposed to one another, and this occurs when reason may be opposed to desire, but the opposition can be manifested only in beings with a sense of time; for the mind commands to resist on account of the future, while desire urges to immediate compliance, as that which is good appears, as the future is unseen, to be absolutely good and absolutely grateful. Thus, the appetitive faculty, in so far as appetitive, may, in a specific sense, be the motor, but it is the object desired by appetite which is the first to set in motion ; for without having been itself moved, it incites to move from having been thought upon or imagined; and there are several such motors. There are three terms here : the motor; then that by which it moves; and thirdly, that which is moved. But the motor is in the two-fold sense of unmoved, and both motor, and moved—the unmoved is the practical good ; the motor and moved is the appetitive stimulus or appetition (for that which is moved moves only in so far as it desires, and appetite is a motion or an act of some kind) ; and the moved is the animal. As the organism by which appetite  effects motion is obviously corporeal, its nature must be studied together with those functions which are common to the body and the Vital Principle. But to speak summarily, the organism whereby motion is effected, is as a hinge in which coexist the beginning and the end of motion—for herein are the convex and the concave, of which that is the beginning, and this the end of motion; and therefore the one is at rest while the other is in motion, as although, rationally considered, the two pieces are distinct, yet, substantively, they are inseperable.

In fine, then, as has been said, an animal is endowed with self-motion to the extent of its appetition; but it cannot be susceptible of appetite without imagination, and all imagination is either rational or sentient, and of this latter kind other animals partake also.


LET us now consider the motor power in such imperfect creatures as have only the sense of Touch; and learn whether or not it is admissible that imagination and desire can be present with them. Now, they do appear to be sensible of pain and pleasure, and if so far sensible, they must of necessity have desire. But how can imagination be present in them? It may, perhaps, be answered that, as their movements are indeterminate, so those sensations are present, but present in some indeterminate manner.

The sentient imagination belongs, as has been said, to other animals, but that which is voluntary is found only in such as are rational; for it is matter of calculation whether this or that shall be done, and as the individual is to pursue what is larger and better, he must be guided by a rule of some kind, and thereby be enabled to individualize several different images. The reason why these creatures do not seem to be capable of forming opinions is, that they are without the faculty for drawing inferences, and this includes opinion. But the appetite has no  deliberative will, as appetite sometimes overcomes and impels the will, and sometimes the will overcomes and impels the appetite, as a ball is bandied to and fro; or appetite rules and impels appetite, when intemperance has the ascendancy. But that which is superior is ever naturally more dominant, and productive of motion in three different directions; but the intelligent faculty has no motion—it remains at rest. Although the conception of the universal is to be distinguished from the conception of the particular, (for while the former says that such an one ought to perform such an act, the latter says that such an one, and that I am he, ought now to perform this particular act,) yet it is this latter opinion rather than the former which impels to move; and although both may be motive, the one, at least, is rather at rest, and the other is rather in motion.


It is necessary to every living creature that it should have a nutritive principle in order that it may live and continue to live, from birth to death; for it is necessary to every thing generated that it should be capable of growth, development and decay, and as these cannot be carried on without nourishment, it is necessary to all reproductive and perishing beings that they should have a congenital nutritive function. But it is not necessary to all living beings that they should be sentient, nor can it be admitted that such as have simple or homogeneous bodies can have Touch, or that there can be an animal without Touch; neither can any beings be sentient but such as are receptive of form without the matter. It is necessary to an animal, however, that it should be sentient, if nature do nothing in vain—for all things in nature are for some end, or else they are accidents of things for some end; so that if there were any animal body fitted for progression without being sentient, it would perish, and could not attain to the end which is nature's design. How, in fact, is such a body to be nourished?  As to creatures which are fixed, they obtain their nourishment on the spot where they have been produced. It is not possible then, that a body which is not fixed to one spot and which has been generated, should have living principle and judging faculties without being sentient. Nor can a creature spontaneously generated be sentient; Why, let us ask, should it be so? The sensibility is for the greater good either of the Vital Principle or the body; but neither of these can, in the case supposed, be effected by it, as the one will not through it think the better, nor the other be better fitted for its offices. Thus, there is no living body free to move which is not sentient. But if a body be sentient, it must necessarily be either homogeneous or compound—Now, homogeneous it cannot be, as in that case it would be without Touch, and Touch it must of necessity have. All which is proved thus—Since an animal is a living body, and all bodies are tangible, and tangible implies whatever is perceptible to Touch, it follows that the body of an animal must be sensible to Touch, if the animal is to preserve its existence. The other senses, as the sight, smell, hearing, perceive through other media; but if an animal when touching were without sensation, it could have no guide for avoiding some things or seizing others, and so circumstanced, it would not be possible for it to preserve its existence. The taste, therefore, is a kind of Touch, for taste is the  sense for food and food is a tangible body; but sound, colour and odour neither nourish nor contribute to growth or decay. Thus, taste must of necessity be a kind of Touch from its being the sense which is perceptive both of what is tangible and nutritive; and, as these two senses are necessary to animals, it is manifest that there can be no animal without Touch.

The other senses, being for the higher good of animals, are allotted, not to all but, only to particular genera, as they are necessary to none but such as have the power of progression. If, indeed, such a creature is to preserve its existence, it must not only be sensible of objects when touching them, but be able also to perceive them when at a distance; and this can be effected if it be sensible through a medium, which, having been impressed and set in motion by the objects of perception reacts upon the percipient. And it is thus that the locomotive impulse acts until it cease in rest—that which impels something else communicates along with impulsion impelling power, and the motion is in a midspace; and as the first motor impels without having been impelled, so the last is impelled without impelling, and the intermediate links, of which there are several, both impel and are impelled. So is it too with respect to changes wrought in bodies, excepting that they are effected without change of locality—as if any one were to tinge a portion of wax, it would be in motion until  it should be saturated; nothing like this, however, can happen to a stone, but it can to water, and that to a distance. The air is mobile in the highest degree, and, provided it be still and in one mass, it both acts and is acted upon. It is better, therefore, in the case of refraction, to assume that the air, in so far as it is one mass, (and it is so over every smooth surface,) is impressed by form and colour, rather than that visual rays issuing from the eye are refracted. Thus, the air, in the case of vision, gives motion to the sense, as if the impress upon wax had been transmitted to its extremity.

It is manifest that an animal body cannot be simple, cannot, I mean, be only fire or air; for an animal cannot have any other sense without having Touch, and every living body is sensible to Touch, as has been said. But all the elements, except earth, may constitute sentient organs, as these all receive impressions through something foreign to themselves and through media; but the Touch is made sensible by touching bodies, and hence its name. And yet the other sentient organs do perceive by Touch, but then it is through something foreign to themselves; while Touch alone seems to perceive directly, through itself. So that an animal body cannot be constituted of any one of the other elements exclusively, nor can it be formed only of earth; for the Touch is the medium, as it were, for tangible impressions, and the organ is perceptive not only of the distinctions which pertain to earth, but of hotcold, and all other tangible qualities. Hence it is that we have no feeling in bones, hair, or other analogous parts because they are of earth; and plants for the same reason, being of  earth have no feeling. It is impossible then that there should be any other sense without that of Touch; and its organ is neither of earth nor any other element exclusively. Thus, it is manifest that the Touch is the only sense of which animals cannot be deprived without dying; that animals only can possess it; and that it alone of the senses is necessary to animal existence. On which account, other sentient impressions in excess (as those of colour, sound and odour) may injure the organs but do not destroy the animal, excepting it be by chance, as when with sound there is an impulse and a blow, or as when, by visual or odorous impressions, other influences are set in motion, which destroy the animal through the Touch and when savour destroys life it does so by communicating simultaneously a tangible impression. But the excess of tangible impression, whether hot, cold or hard, destroys the animal, because as every impression in excess destroys the sentient organ, so the tangible destroys that of Touch, and it is by the Touch that animal life has been defined; and it has been shewn that an animal cannot possibly exist without the Touch. Thus, the excess of tangible impressions destroys not the organ only but the animal, as that sense alone is necessary to its existence. Animals, in fact, possess, as has been said, the other senses, not merely for existence but, for higher enjoyment: they have sight, in order that, as they live  in air and water, in a transparent medium in short, they may see; taste, that by discerning what is grateful or nauseous in food they may have desire for and move to obtain it; hearing, that others may signify something to them, and a tongue that they may signify something to others.