Amongst the special sciences treated by Aristotle, the Physics is contained in a whole series of physical treatises, which form a tolerably complete system of what constitutes the Philosophy of Nature in its whole extent. We shall try to give their general plan. Aristotle’s first work is his Treatise, in eight books, on Physics, or on the Principles (φυσικὴ ἀκρόασις ἢ περὶ ἀρχῶν). In this he deals, as is fitting, with the doctrine of the Notion of nature generally, with movement, and with space and time. The first manifestation of absolute substance is movement, and its moments are space and time; this conception of its manifestation is the universal, which realizes itself first in the corporeal world, passing into the principle of separation. Aristotle’s Physics is what for present physicists would, properly speaking, be the Metaphysics of Nature; for our physicists only say what they have seen, what delicate and excellent instruments they have made, and not what they have thought. This first work by Aristotle is followed by his treatises concerning the Heavens, which deal with the nature of body and the first real bodies, the earth and heavenly bodies in general, as also with the general abstract relation of bodies to one another through mechanical weight and lightness, or what we should call attraction; and finally, with the determination of abstract real bodies or elements. Then follow the treatises on Production and Destruction, the physical process of change, while formerly the ideal process of movement was considered. Besides the physical elements, moments which are only posited in process, as such, now enter in: for instance, warmth, cold, &c. Those elements are the real existent facts, while these determinations are the moments of becoming or of passing away, which exist only in movement. Then comes the Meteorology; it represents the universal physical process in its most real forms. Here particular determinations appear, such as rain, the saltness of the sea, clouds, dew, hail, snow, hoar-frost, winds, rainbows, boiling, cooking, roasting, colours, &c. On certain matters, such as the colours, Aristotle wrote particular treatises. Nothing is forgotten, and yet the presentation is, on the whole, empiric. The book On the Universe, which forms the conclusion, is said not to be genuine; it is a separate dissertation, addressed to Alexander, which contains in part the doctrine of the universality of things, a doctrine found already in the other treatises; hence this book does not belong to this series.
From this point Aristotle proceeds to organic nature, and here his works not only contain a natural history, but also a physiology and anatomy. To the anatomy pertain his works on the Locomotion of Animals, and on the Parts of Animals. He deals with physiology in the works on the Generation of Animals, on the common Movement of Animals; and then he comes to the distinction between Youth and Age, Sleeping and Waking, and treats of Breathing, Dreaming, the Shortness and Length of Life, &c., all of which he deals with partly in an empiric, and partly in a more speculative manner. Finally, there comes the History of Animals, not merely as a history of Nature, but also as the history of the animal in its entirety—what we may call a kind of physiologico-anatomical anatomy. There is likewise a botanical work On Plants (περὶ φυτῶν) which is ascribed to him. Thus we here find natural philosophy in the whole extent of its outward content.
As regards this plan, there is no question that this is not the necessary order in which natural philosophy or physics must be treated. It is long since physics adopted in its conception the form and tendency derived from Aristotle, of deducing the parts of the science from the whole; and thus even what is not speculative still retains this connection as far as outward order goes. This is plainly to be preferred to the arrangement in our modern text-books, which is a wholly irrational succession of doctrines accidentally put together, and is undoubtedly more suitable to that method of contemplating nature, which grasps the sensuous manifestation of nature quite irrespective of sense or reason. Physics before this contained some metaphysics, but the experience which was met with in endeavouring unsuccessfully to work it out, determined the physicists, so far as possible, to keep it at a distance, and to devote their attention to what they call experience, for they think that here they come across genuine truth, unspoiled by thought, fresh from the hand of nature; it is in their hands and before their faces. They can certainly not dispense with the Notion, but through a kind of tacit agreement they allow certain conceptions, such as forces, subsistence in parts, &c., to be valid, and make use of these without in the least knowing whether they have truth and how they have truth. But in regard to the content they express no better the truth of things, but only the sensuous manifestation. Aristotle and the ancients understand by physics, on the other hand, the comprehension of nature—the universal; and for this reason Aristotle also calls it the doctrine of principles. For in the manifestation of nature this distinction between the principle and what follows it, manifestation, really commences, and it is abrogated only in genuine speculation. Yet if, on the one hand, what is physical in Aristotle is mainly philosophic and not experimental, he yet proceeded in his Physics in what may be called an empiric way. Thus, as it has been already remarked of the Aristotelian philosophy in general that the different parts fall into a series of independently determined conceptions, so we find that this is the case here also; hence an account can only be given of a part of them. One part is not universal enough to embrace the other part, for each is independent. But that which follows, and which has in great measure reference to what is individual, no longer comes under the dominion of the Notion, but becomes a superficial suggestion of reasons, and an explanation from the proximate causes, such as we find in our physics.
In regard to the general conception of nature, we must say that Aristotle represents it in the highest and truest manner. For in the Idea of nature Aristotle (Phys. II. 8) really relies on two determinations: the conception of end and the conception of necessity. Aristotle at once grasps the whole matter in its principles, and this constitutes the old contradiction and divergence of view existing between necessity (causæ efficientes) and end (causæ finales), which we have inherited. The first mode of consideration is that in accordance with external necessity, which is the same as chance—the conception that all that pertains to nature is determined from without by means of natural causes. The other mode of consideration is the teleological, but conformity to end is either inward or outward, and in the more recent culture the latter has long retained the supremacy. Thus men vibrate in their opinion between these two points of view, seek external causes, and war against the form of an external teleology which places the end outside of nature. These determinations were known to Aristotle, and he thoroughly investigates them and considers what they are and mean. Aristotle’s conception of nature is, however, nobler than that of to-day, for with him the principal point is the determination of end as the inward determinateness of natural things. Thus he comprehended nature as life, i.e. as that which has its end within itself, is unity with itself, which does not pass into another, but, through this principle of activity, determines changes in conformity with its own content, and in this way maintains itself therein. In this doctrine Aristotle has before his eyes the inward immanent end, to which he considers necessity an external condition. Thus, on the one hand, Aristotle determines nature as the final cause, which is to be distinguished from what is luck or chance; it is thus opposed by him to what is necessary, which it also contains within itself; and then he considers how necessity is present in natural things. In nature we usually think of necessity first, and understand as the essentially natural that which is not determined through end. For long men thought that they determined nature both philosophically and truly in limiting it to necessity. But the aspect of nature has had a stigma removed from it, because, by means of its conformity to the end in view, it is elevated above the commonplace. The two moments which we have considered in substance, the active form and matter, correspond with these two determinations.
We must first consider the conception of adaptation to end as the ideal moment in substance. Aristotle begins (Phys. II. 8) with the fact that the natural is the self-maintaining, all that is difficult is its comprehension. “The first cause of perplexity is, what hinders nature from not operating for the sake of an end, and because it is better so to operate, but” being, for example, “like Jupiter, who rains, not that the corn may grow, but from necessity. The vapour driven upwards cools, and the water resulting from this cooling falls as rain, and it happens that the corn is thereby made to grow. In like manner, if the corn of any one is destroyed, it does not rain for the sake of this destruction, but this is an accidental circumstance.” That is to say, there is a necessary connection which, however, is an external relation, and this is the contingency of the cause as well as of the effect. “But if this be so,” Aristotle asks, “what hinders us from assuming that what appears as parts” (the parts of an animal, for instance) “may thus subsist in nature, too, as contingent? That, for example, the front teeth are sharp and adapted for dividing, and that the back teeth, on the contrary, are broad and adapted for grinding the food in pieces, may be an accidental circumstance, not necessarily brought about for these particular ends. And the same is true with respect to the other parts of the body which appear to be adapted for some end; therefore those living things in which all was accidentally constituted as if for some end, are now, having once been so existent, preserved, although originally they had arisen by chance, in accordance with external necessity.” Aristotle adds that Empedocles especially had these reflections, and represented the first beginnings of things as a world composed of all sorts of monstrosities, such as bulls with human heads; such, however, could not continue to subsist, but disappeared because they were not originally constituted so that they should endure; and this went on until what was in conformity with purpose came together. Without going back to the fabulous monstrosities of the ancients, we likewise know of a number of animal tribes which have died out, just because they could not preserve the race. Thus we also require to use the expression development (an unthinking evolution), in our present-day natural philosophy. The conception that the first productions were, so to speak, attempts, of which those which did not show themselves to be suitable could not endure, is easily arrived at by natural philosophy. But nature, as entelecheia or realization, is what brings forth itself. Aristotle hence replies: “It is impossible to believe this. For what is produced in accordance with nature is always, or at least for the most part, produced” (external universality as the constant recurrence of what has passed away), “but this is not so with what happens through fortune or through chance. That in which there is an end (τέλος), equally in its character as something which precedes and as something which follows, is made into end; as therefore a thing is made, so is its nature, and as is its nature, so is it made; it exists therefore for the sake of this.” The meaning of nature is that as something is, it was in the beginning; it means this inward universality and adaptation to end that realizes itself; and thus cause and effect are identical, since all individual parts are related to this unity of end. “He who assumes contingent and accidental forms, subverts, on the other hand, both nature itself and that which subsists from nature, for that subsists from nature which has a principle within itself, by whose means, and being continually moved, it attains its end.” In this expression of Aristotle’s we now find the whole of the true profound Notion of life, which must be considered as an end in itself—a self-identity that independently impels itself on, and in its manifestation remains identical with its Notion: thus it is the self-effectuating Idea. Leaves, blossoms, roots thus bring the plant into evidence and go back into it; and that which they bring to pass is already present in the seed from which they took their origin. The chemical product, on the contrary, does not appear to have itself similarly present, for from acid and base a third appears to come forth; but here, likewise, the essence of both these sides, their relationship, is already present, though it is there mere potentiality, as it is in the product merely a thing. But the self-maintaining activity of life really brings forth this unity in all relationships. What has here been said is already contained in that which was asserted by those who do not represent nature in this way, but say, “that which is constituted as though it were constituted for an end, will endure.” For this is the self-productive action of nature. In the modern way of looking at life this conception becomes lost in two different ways; either through a mechanical philosophy, in which we always find as principle pressure, impulse, chemical relationships and forces, or external relations generally—which certainly seem to be inherent in nature, but not to proceed from the nature of the body, seeing that they are an added, foreign appendage, such as colour in a fluid; or else theological physics maintain the thoughts of an understanding outside of the world to be the causes. In the Kantian philosophy we for the first time have that conception once more awakened in us, for organic nature at least; life has there been made an end to itself. In Kant this indeed had only the subjective form which constitutes the essence of the Kantian philosophy, in which it seems as though life were only so determined by reason of our subjective reasoning; but still the whole truth is there contained that the organic creation is the self-maintaining. The fact that most recent times have brought back the rational view of the matter into our remembrance, is thus none else than a justification of the Aristotelian Idea.
Aristotle also speaks of the end which is represented by organic nature in itself, in relation to the means, of which he says (Phys. II. 8): “If the swallow builds her nest, and the spider spreads her web, and trees root themselves in the earth, for the sake of nutriment, there is present in them a self-maintaining cause of this kind, or an end.” For this instinctive action exhibits an operation of self-preservation, as a means whereby natural existence becomes shut up and reflected into itself. Aristotle then brings what is here said into relation with general conceptions which he had earlier maintained (p. 138): “Since nature is twofold as matter and form, but since the latter is end, and the rest are on account of the end, this is final cause.” For the active form has a content, which, as content of potentiality, contains the means which make their appearance as adapted for an end, i.e. as moments established through the determinate Notion. However much we may, in the modern way of regarding things, struggle against the idea of an immanent end, from reluctance to accept it, we must, in the case of animals and plants, acknowledge such a conception, always re-establishing itself in another. For example, because the animal lives in water or in air, it is so constructed that it can maintain its existence in air or water; thus it requires water to explain the gills of fishes; and, on the other hand, because the animal is so constructed, it lives in water. This activity in transformation thus does not depend in a contingent way on life; it is aroused through the outward powers, but only in as far as conformity with the soul of the animal permits.
In passing, Aristotle here (Phys. II. 8) makes a comparison between nature and art, which also connects what results with what goes before, in accordance with ends. “Nature may commit an error as well as art; for as a grammarian sometimes makes a mistake in writing, and a physician in mixing a medicinal draught, nature, too, sometimes does not attain its ends. Its errors are monstrosities and deformities, which, however, are only the errors of that which operates for an end. In the production of animals and plants, an animal is not at first produced, but the seed, and even in it corruption is possible.” For the seed is the mean, as being the not as yet established, independent, indifferent, free actuality. In this comparison of nature with art we ordinarily have before us the external adaptation to end, the teleological point of view, the making for definite ends. And Aristotle declaims against this, while he remarks that if nature is activity for a certain end, or if it is the implicitly universal, “it is absurd to deny that action is in conformity with end, because that which moves cannot be seen to have deliberated and considered.” The understanding comes forward with the determination of this end, and with its instruments and tools, to operate on matter, and we carry this conception of an external teleology over into nature. “But art also,” says Aristotle, “does not deliberate. If the form of a ship were the particular inward principle of the timber, it would act as nature prompted. The action of nature is very similar to the exercise of the art whereby anyone heals himself.” Through an inward instinct the animal avoids what is evil, and does what is good for him; health is thus essentially present to him, not as a conscious end, but as an understanding which accomplishes its ends without conscious thought.
As Aristotle has hitherto combated an external teleology, he directs another equally applicable remark (Phys. II. 9) against merely external necessity, and thus we come to the other side, or to how necessity exists in nature. He says in this regard: “Men fancy that necessity exists in this way in generation, just as if it were thought that a house existed from necessity, because heavy things were naturally carried downwards, and light things upwards, and that, therefore, the stones and foundation, on account of their weight, were under the earth, and the earth, because it was lighter, was further up, and the wood in the highest place because it is the lightest.” But Aristotle thus explains the facts of the case. “The house is certainly not made without these materials, but not on account of, or through them (unless the material so demands), but it is made for the sake of concealing and preserving certain things. The same takes place in everything which has an end in itself; for it is not without that which is necessary to its nature, and yet it is not on account of this, unless the matter so demands, but on account of an end. Hence the necessary is from hypothesis only, and not as end, for necessity is in matter, but end is in reason (λόγῳ). Thus it is clear that matter and its movement are necessity in natural things; both have to be set forth as principle, but end is the higher principle.” It undoubtedly requires necessity, but it retains it in its own power, does not allow it to give vent to itself, but controls external necessity. The principle of matter is thus turned into the truly active ground of end, which means the overthrow of necessity, so that that which is natural shall maintain itself in the end. Necessity is the objective manifestation of the action of its moments as separated, just as in chemistry the essential reality of both the extremes—the base and the acid—is the necessity of their relation.
This is the main conception of Aristotelian Physics. Its further development concerns the conceptions of the different objects of nature, a material for speculative philosophy which we have spoken of above (pp. 153-155), and regarding which Aristotle puts before us reflections both difficult and profound. Thus he at first (Phys. III. 1-3) proceeds from this point to movement (κίνησις), and says that it is essential that a philosophy of nature should speak of it, but that it is difficult to grasp; in fact, it is one of the most difficult conceptions. Aristotle thus sets to work to understand movement in general, not merely in space and time, but also in its reality; and in this sense he calls it “the activity of an existent thing which is in capacity, so far as it is in capacity.” He explains this thus: “Brass is in capacity a statue; yet the motion to become a statue is not a motion of the brass so far as it is brass, but a motion of itself, as the capacity to become a statue. Hence this activity is an imperfect one (ἀτελής),” i.e. it has not its end within itself, “for mere capacity, whose activity is movement, is imperfect.” The absolute substance, the moving immovable, the existent ground of heaven which we saw as end, is, on the contrary, both activity itself and the content and object of activity. But Aristotle distinguishes from this what falls under the form of this opposition, “That moving is also moved which has movement as a capacity, and whose immobility is rest. That in which movement is present has immobility as rest; for activity in rest, as such, is movement.” That is to say, rest is capacity for motion. “Hence movement is the activity of that which is movable (κινητοῦ),[93] so far as it is movable; but this happens from the contact of that which is motive (κινητικοῦ), so that at the same time it is posited as passive likewise. But that which moves always introduces a certain form or end (εἶδος), either this particular thing (τόδε), or a quality or a quantity, which is the principle and cause of the motion when it moves; thus man, as he is in energy, makes man from man as he is in capacity. Thus, too, it is evident that movement is in the movable thing: for it is the activity of this, and is derived from that which is motive. The activity of that which is motive is likewise not different, for both are necessarily activity. It is motive because it has the capacity for being so; but it causes motion because it energizes. But it is the energetic of the moveable (ἔστιν ἐνεργητικὸν τοῦ κινετοῦ), so that there is one energy of both; just as the relation between one and two is the same as that between two and one, and there also is the same relation between acclivity and declivity, so the way from Thebes to Athens is the same as from Athens to Thebes. Activity and passivity are not originally (κυρίως) the same, but in what they are inherent, in motion, they are the same. In Being (τῷ εἶναι) they are identical, but activity, in so far as it is activity of this in this” (what is moved), “and the activity of this from this” (what moves), “is different as regards its conception (τῷ λόγῳ).” Aristotle subsequently deals with the infinite (Phys. III. 4-8).
“In like manner it is necessary,” says Aristotle (Phys. IV. 1-5), “that the natural philosopher should consider the subject of place (τόπος).” Here come various definitions and determinations under which space generally and particular space or place appear. “Is place a body? It cannot be a body, for then there would be in one and the same, two bodies. Again, if it is the place and receptacle (χώρα) of this body, it is evident that it is so also of the superficies and the remaining boundaries; but the same reasoning applies to these, for where the superficies of water were before, there will now be the superficies of air,” and thus the places of both superficies would be in one. “But in truth there is no difference between the point and the place of the point, so that if place is not different from the other forms of limitation, neither is it something outside of them. It is not an element, and neither consists of corporeal nor of incorporeal elements, for it possesses magnitude, but not body. The elements of bodies are, however, themselves bodies, and no magnitude is produced from intelligible elements. Place is not the material of things, for nothing consists of it—neither the form, nor the Notion, nor the end, nor the moving cause; and yet it is something.” Aristotle now determines place as the first unmoved limit of that which is the comprehending: it comprehends the body whose place it is, and has nothing of the thing in itself; yet it co-exists with the thing, because the limits and the limited co-exist. The uttermost ends of what comprehends and of what is comprehended are identical, for both are bounds; but they are not bounds of the same, for form is the boundary of the thing, place is that of the embracing body. Place, as the comprehending, remains unchangeably passive while the thing which is moved is moved away; from which we see that place must be separable from the thing. Or place, according to Aristotle, is the boundary, the negation of a body, the assertion of difference, of discretion; but it likewise does not merely belong to this body, but also to that which comprehends. There is thus no difference at all, but unchangeable continuity. “Place is neither the universal (κοινός) in which all bodies are” (heaven), “nor the particular (ἴδιος), in which they are as the first (πρώτῳ).” Aristotle also speaks of above and below in space, in relation to heaven as that which contains, and earth as what is beneath. “That body, outside of which is a comprehending body, is in space. But the whole heavens are not anywhere, since no body comprehends them. Outside the universe nothing is, and hence everything is in the heavens, for the heavens are the whole. Place, however, is not the heavens, but its external quiescent boundary which touches the body moved. Hence the earth is in water, water in air, air in ether, but ether in the heavens.”
From this point Aristotle goes on (Phys. IV. 6, 7) to empty space, in which an old question is involved which physicists even now cannot explain: they could do so if they studied Aristotle, but as far as they are concerned there might have been no thought nor Aristotle in the world. “Vacuum, according to ordinary ideas, is a space in which there is no body, and, fancying that all Being is body, they say that vacuum is that in which there is nothing at all. The conception of a vacuum has its justification for one thing in the fact that a vacuum,” the negative to an existent form, “is essential to motion; for a body could not move in a plenum,” and in the place to which it does move there must be nothing. “The other argument in favour of a vacuum is found in the compression of bodies, in which the parts press into the empty spaces.” This is the conception of varying density and the alteration of the same, in accordance with which an equal weight might consist of an equal number of parts, but these, as being separated by vacuum, might present a greater volume. Aristotle confutes these reasonings most adroitly, and first of all in this way; “The plenum could be changed, and bodies could yield to one another even if no interval of vacuum separated them. Liquids as well as solids are not condensed into a vacuum; something that they contained is expelled, just as air is expelled if water is compressed.”
Aristotle deals more thoroughly, in the first place (Phys. IV. 8), with the erroneous conception that the vacuum is the cause of movement. For, on the one hand, he shows that the vacuum really abolishes motion, and consequently in vacuum a universal rest would reign. He calls it perfect indifference as to the greater or less distance to which a thing is moved; in vacuum there are no distinctions. It is pure negation without object or difference; there is no reason for standing still or going on. But body is in movement, and that, indeed, as distinguished; it has a positive relation, and not one merely to nothing. On the other hand, Aristotle refutes the idea that movement is in vacuum because compression is possible. But this does not happen in a vacuum; there would be established in it not one movement, but a movement towards all sides, a general annihilation, an absolute yielding, where no cohesion would remain in the body. “Again, a weight or a body is borne along more swiftly or more slowly from two causes; either because there is a difference in that through which it is borne along, as when it moves through air or water or earth, or because that which is borne along differs through excess of weight or lightness.” As regards difference of movement on account of the first difference—that in the density of the medium—Aristotle says: “The medium through which the body is borne along is the cause of the resistance encountered, which is greater if the medium is moving in a contrary direction (and less if it is at rest); resistance is increased also if the medium is not easily divided. The difference in velocity is in inverse ratio to the specific gravity of the medium, air and water, so that if the medium has only half the density, the rate of progress will be double as quick. But vacuum has to body no such relation of differences of specific gravity. Body can no more contain a vacuum within its dimensions than a line can contain a point, unless the line were composed of points. The vacuum has no ratio to the plenum.” But as to the other case, the difference in weight and lightness, which has to be considered as being in bodies themselves, whereby one moves more quickly than another through the same space: “this distinction exists only in the plenum, for the heavy body, by reason of its power, divides the plenum more quickly.” This point of view is quite correct, and it is mainly directed against a number of conceptions that prevail in our physics. The conception of equal movement of the heavy and the light, as that of pure weight, pure matter, is an abstraction, being taken as though they were inherently like, only differing through the accidental resistance of the air.
Aristotle (Phys. IV. 9) now comes to the second point, to the proof of the vacuum because of the difference in specific gravity. “Many believe that the vacuum exists because of the rare and the dense;” the former is said to be a rare body, and the latter a perfect continuity; or they at least differ quantitatively from one another through greater or less density. “For if air should be generated from a quantity of water, a given quantity of water must produce a quantity of air the same in bulk, or there must necessarily be a vacuum; for it is only on the hypothesis of a vacuum that compression and rarefaction are explicable. Now if, as they say, the less dense were that which has many separate void spaces, it is evident that since a vacuum cannot be separated any more than a space can have intervals, neither can the rare subsist in this manner. But if it is not separable, and yet a vacuum is said to exist in the body, in the first place movement could thus only be upwards; for the rare is the light, and hence they say that fire is rare,” because it always moves upwards. “In the next place the vacuum cannot be the cause of motion as that in which something moves, but must resemble bladders that carry up that which adheres to them. But how is it possible that a vacuum can move, or that there can be a place where there is a vacuum? For that into which it is carried would be the vacuum of a vacuum. In short, as there can be no movement in vacuum, so also a vacuum cannot move.” Aristotle set against these ideas the true state of matters, and states generally the ideal conception of nature: “that the opposites, hot and cold, and the other physical contraries, have one and the same matter, and that from what is in capacity that which is in energy is produced; that matter is not separable though it is different in essence[94] (τῷ εἶναι), and that it remains one and the same in number (ἀριθμῷ) even if it possesses colour, or is hot and cold. And again, the matter of a small body and a large is the same, because at one time a greater proceeds from a smaller, and at another time a smaller from a greater. If air is generated from water it is expanded, but the matter remains the same and without taking to itself anything else; for that which it was in capacity it becomes in actuality. In a similar way if air is compressed from a greater into a less volume, the process will be reversed, and air will similarly pass into water, because the matter which is in capacity both air and water, also becomes both.” Aristotle likewise asserts that increase and decrease of warmth, and its transition into cold, is no addition or otherwise of warm matter, and also one and the same is both dense and rare. This is very different from the physical conceptions which assert more or less matter to correspond with more or less density, thus comprehending the difference in specific weight as the external addition of matter. Aristotle, on the contrary, takes this dynamically, though certainly not in the sense in which dynamics are to-day understood, viz. as an increase of intensity or as a degree, for he accepts intensity in its truth as universal capacity. Undoubtedly the difference must also be taken as a difference in amount, but not as an increase and decrease, or as an alteration in the absolute quantity of the matter. For here intensity means force, but again not as being a thing of thought separated from matter, but as indicating that if anything has become more intensive, it has had its actuality diminished, having, however, according to Aristotle, attained to a greater capacity. If the intensity is again directed outwards, and compared with other things, it undoubtedly becomes degree, and therefore magnitude immediately enters in. It then is indifferent whether greater intension or greater extension is posited; more air is capable of being warmed to the same degree as less, through the greater intensity of the warmth; or the same air can thereby become intensively warmer.
As regards the investigation of time, Aristotle remarks (Phys. IV. 10, 11, 13) that if time is externally (exoterically, ἐξωτερικῶς) regarded, we are inevitably led to doubt (διαπορῆσαι) whether it has any being whatever, or whether it has bare existence, as feeble (μόλις καὶ ἀμυδρῶς) as if it were only a potentiality. “For one part of it was and is not: another part will be and is not as yet; but of these parts infinite and everlasting (ἀεὶ λαμβανόμενος), time is composed. But it now appears that time, if composed of things that are not, may be incapable of existence. And also as regards everything divisible, if it exists, either some or all of its parts must be. Time is certainly divisible; but some of the parts are past, others are future, and no part is present. For the now is no part, since a part has a measure, and the whole must consist of the parts; but time does not appear to consist of the Now.” That is to say, because the Now is indivisible, it has no quantitative determination which could be measured. “Besides it is not easy to decide whether the Now remains, or always becomes another and another. Again, time is not a movement and change, for movement and change occur in that which is moved and changed, or accompany time in its course; but time is everywhere alike. Besides change is swifter and slower, but time is not. But it is not without change and motion” (which is just the moment of pure negativity in the same) “for when we perceive no change, it appears as if no time had elapsed, as in sleep. Time is hence in motion but not motion itself.” Aristotle defines it thus: “We say that time is, when we perceive the before and after in movement; but these are so distinguished that we apprehend them to be another and another, and conceive that there is something between, as a middle. Now when we understand that the extremes of the conclusion are different from the middle, and the soul says that the Now has two instants, the one prior and the other posterior, then we say that this is time. What is determined through the Now, we call time, and this is the fundamental principle. But when we are sensible of the Now as one, and not as a prior and posterior in motion, nor as the identity of an earlier or later, then there does not appear to us to have been any time, because neither was there any motion.” Tedium is thus ever the same. “Time is hence the number of motion, according to priority and posteriority; it is not motion itself, unless so far as motion has number. We judge of the more or less through number, but of a greater or less motion by time. But we call number that which can be numbered, as well as that with which we number; but time is not the number with which we number, but that which is numbered, and, like motion, always is changing. The Now is, which is the unity of number, and it measures time. The whole of time is the same, for the Now which was is the same” (universality as the Now destroyed) “but in Being it is another. Time thus is through the Now both continuous (συνεχής) and discrete (διῇρηται). It thereby resembles the point, for that also is the continuity of the line and its division, its principle and limit; but the Now is not an enduring point. As continuity of time the Now connects the past and the future, but it likewise divides time in capacity,” the Now is only divisibility and the moments only ideal. “And in as far as it is such, it is always another; but, in as far as it unites, it is ever one and the same. Similarly, in as far as we divide the line, other and yet other points always arise for thought; but in as far as it is one, there is only one point. Thus the Now is both the division of time in capacity, and the limit and union of both” i.e. of the prior and posterior. The universally dividing point is only one as actual; but this actual is not permanently one, but ever and again another, so that individuality has universality, as its negativity, within it. “But division and union are the same, and similarly related; however their Notion (τὸ εἶναι)[95] is different.” In one and the same respect the absolute opposite of what was posited is immediately set forth as existent; in space, on the other hand, the moments are not set forth as existent, but in it first appears this being and its motion and contradiction. Thus the identity of the understanding is not a principle with Aristotle, for identity and non-identity to him are one and the same. Because the Now is only now, past and future are different from it, but they are likewise necessarily connected in the Now, which is not without before and after; thus they are in one, and the Now, as their limit, is both their union and their division.
Aristotle (Phys. V. 1) then goes on to movement as realized in a thing, to change (μεταβολή) or to the physical processes—while before we had pure movement. “In movement there is first something which moves, also something which is moved, and the time in which it is moved; besides these, that from which, and that into which it is moved.” (Cf. supra, p. 141.) “For all motion is from something and into something; but there is a difference between that which is first moved and that into which and from which it is moved, as, for instance, wood, warmth and cold. The motion is in the wood and not in the form; for neither form nor place, nor quantity moves or is moved, but” (in the order in which they follow) “there is that which is moved and that which moves, and that into which it is moved. That to which movement is made, more than that out of which movement is made, is named change. Hence to pass into non-being is also change, although what passes away is changed from Being: and generation is a mutation into Being, even though it is from non-being.” The remark is to be interpreted as meaning that for the first time in real becoming motion, i.e. in change, the relation whereto enters, while the relation wherefrom is that in which change is still the mere ideal motion. Besides this first form of difference between motion and change, Aristotle further gives another, since he divides change into three: “into change from a subject (ἐξ ὑποκειμένον) into a subject; or from a subject into a non-subject; or from a non-subject into a subject.” The fourth, “from a non-subject into a non-subject,” which may also appear in the general division, “is no mutation, for it contains no opposition.” It may certainly be merely thought or ideal, but Aristotle indicates the actual phenomenon. “The mutation from a non-subject into a subject is generation (γένεσις); that from a subject into a non-subject is corruption (φθορά); that from a subject into a subject, is motion as such;” because that which is transformed remains the same, there is no becoming-another of the actual, but a merely formal becoming-another. This opposition of the materialized motion as mutation, and of merely formal motion, is noteworthy.
In the sixth book Aristotle comes to the consideration of the dialectic of this motion and change as advanced by Zeno, that is, to the endless divisibility which we have already (Vol. I. pp. 266-277) considered. Aristotle solves it through the universal. He says that they are the contradiction of the universal turned against itself; the unity in which its moments dissolve is not a nothing, so that motion and change are nothing, but a negative universal, where the negative is itself again posited as positive, and that is the essence of divisibility.
Of the further details into which Aristotle enters, I shall only give the following. As against atoms and their motion, he remarks (Phys. VI. 10) that the indivisible has no motion and mutation, which is the direct opposite of the proposition of Zeno that only simple indivisible Being and no motion exists. For as Zeno argues from the indivisibility of atoms against motion, Aristotle argues from motion against atoms. “Everything which moves or changes is in the first division of this time partly here and partly there. The atom, as simple indivisible Being, can, however, not have any part of it in both points in space, because it then would be divisible. The indivisible could thus only move if time consisted of the Now; this is, however, impossible, as we proved before.” Because atoms thus neither have change in themselves, nor can this come to them from without through impulse, &c., they are really without truth.
The determination of the pure ideality of change is important. Aristotle says of this (Phys. VII. 3), “That which is changed is alone the sensuous and perceptible (αἰσθητόν); and forms and figures, as also capacities, are not changed, they arise and disappear in a thing only, without being themselves changed.” In other words: the content of change is unchangeable; change as such belongs to mere form. “Virtues or vices belong, for example, to habits acquired. Virtue is the perfection (τελείωσις) in which something has reached the end of its nature. Vice, however, is the corruption and non-attainment of this. They are not changes, for they only arise and pass away while another alters.” Or the difference becomes a difference of Being and non-being, i.e. a merely sensuous difference.
From these conceptions Aristotle now comes nearer to the first real or physical motion (Phys. VIII. 6, 8, 9; De C\nlo, I. 4): The first principle of motion is itself unmoved. An endless motion in a straight line is an empty creation of thought; for motion is necessarily an effort after something. The absolute motion is the circular, because it is without opposition. For because movement has to be considered in regard to the starting-place and the end in view, in the straight movement the directions from A to B and from B to A are opposed, but in motion in a circle they are the same. The idea that heavenly bodies would of themselves have moved in a straight line, but that they accidentally came into the sphere of solar attraction, is an empty reflection which is far from occurring to Aristotle.
Aristotle then shows (De C\nlo, II. I; I. 3) that “the whole heavens neither arose nor can pass away, for they are one and eternal: they neither have beginning nor end in eternal time, for they contain infinite time shut up within them.” All the other ideas are sensuous which try to speak of essential reality, and in them there always is that present which they think they have excluded. For when they assert a vacuum before the beginning of generation, this is the quiescent, self-identical, i.e. the eternal matter, which is thus already established before origination; they will not allow that before origination nothing exists. But in fact a thing does not exist before its origination, i.e. in movement there is something to move, and where reality is, there is motion. They do not, however, bring together that vacuum, the self-identical, the un-originated matter and this nothing. “That which has this absolute circular movement is neither heavy nor light; for the heavy is what moves downwards, and the light what moves upwards.” In modern physics the heavenly bodies, on the other hand, are endowed with weight, and seek to rush into the sun, but cannot do so on account of another force. “It is indestructible and ungenerated, without decrease or increase, without any change. It is different from earth, fire, air and water; it is what the ancients called ether, as the highest place, from its continuous course (ἀεὶ θεῖν) in infinite time.” This ether thus appears to be eternal matter which does not, however, take such a definite form, but which remains as it is, just as the heavens do in our conception, although here the juxtaposition begins ever to strike us more forcibly.
Aristotle (De C\nlo, III. 6) shows further that the elements do not proceed from one body, but from one another; for in generation they neither proceed from what is incorporeal, nor from what is corporeal. In the first case they would have sprung from the vacuum, for the vacuum is the immediate incorporeal; but in that case the vacuum must have existed independently as that in which determinate corporeality arose. But neither do the elements arise from a corporeal, for else this body itself would be a corporeal element before the elements. Thus it only remains that the elements must spring from one another. Regarding this we must remark that Aristotle understands by origination, actual origination—not the transition from the universal to the individual, but the origination of one determinate corporeal, not from its principle, but from the opposite as such. Aristotle does not consider the universal as it contains the negative within it; else the universal would be the absolute matter whose universality, as negativity, is set forth, or is real.
From this point Aristotle comes (De C\nlo, IV. I-5) to a kind of deduction of the elements, which is noteworthy. He shows that there must be four of them, in the following way—because he starts from the fundamental conceptions of weight and of lightness, or what we should call attraction and centrifugal force. The corporeal, he says, in its motion is neither light nor heavy, and, indeed, it is not only relative but also absolute. The relatively light and heavy is what, while equal in volume, descends more slowly or quickly. Absolute lightness goes up to the extremity of the heavens, absolute weight down into the middle. These extremes are fire and earth. Between these there are mediums, other than they, which relate to one another like them; and these are air and water, the one of which has weight, and the other lightness, but only relatively. For water is suspended under everything except earth, and air over everything except fire. “Hence,” Aristotle concludes, “there now are these four matters, but they are four in such a way that they have one in common; more particularly, because they arise out of one another, but exist as different.” Yet it is not the ether that Aristotle designates as this common matter. We must in this regard remark that however little these first determinations may be exhaustive, Aristotle is still far further on than the moderns, since he had not the conception of elements which prevails at the present time, according to which the element is made to subsist as simple. But any such simple determination of Being is an abstraction and has no reality, because such existence would be capable of no motion and change; the element must itself have reality, and it thus is, as the union of opposites, resolvable. Aristotle hence makes the elements, as we have already seen with those who went before (Vol. I., pp. 181, 182; 290-293; 336), arise out of one another and pass into one another; and this is entirely opposed to our Physics, which understands by elements an indelible, self-identical simplicity only. Hence men are wonderfully discerning in reproaching us for calling water, air, &c., elements! Nor yet in the expression “neutrality” have the modern physicists been able to grasp a universality conceived of as a unity, such as Aristotle ascribes to the elements; in fact, however, the acid which unites with a base is no longer, as is asserted, present within it as such. But however removed Aristotle may be from understanding simplicity as an abstraction, just as little does he recognize here the arid conception of consisting of parts. Quite the contrary. He strives enough against this, as, for instance, in relation to Anaxagoras (De C\nl. III. 4).
I shall further mention the moments of the real process in relation to motion, in which Aristotle finally passes on (De gen. et corr. II. 2-4) to the “principles of perceptible body”; we here see the elements in process, as formerly in their restful determinateness. Aristotle excludes the relations which concern sight, smell, &c., and brings forward the others as being those which are of sensible weight or lightness. He gives as these fundamental principles—warmth and cold, dryness and moisture; they are the sensible differences for others, while weight and lightness are different for themselves. Now in order to prepare for the transition of the elements into sensible relations, Aristotle says: “Because there are those four principles, and four things have properly six relations to one another, but the opposite cannot here be connected (the moist cannot be connected with the dry, or the warm with the cold), there are four connections of these principles, warm and dry, warm and moist, cold and moist, cold and dry. And these connections follow those first elements, so that thus fire is warm and dry, air warm and moist (vapour), water cold and moist, earth cold and dry.” From this Aristotle now makes the reciprocal transformation of the elements into one another comprehensible thus: Origination and decay proceed from the opposite and into the opposite. All elements have a mutual opposite; each is as non-being to the Being of the other, and one is thus distinguished from the other as actuality and capacity. Now amongst these some have an equal part in common; fire and water, for example, have warmth; thus if in fire dryness were overcome by moisture, out of fire air would arise. On the contrary, as regards those which have nothing in common with one another, like earth, which is cold and dry, and air, which is warm and moist, the transition goes more slowly forward. The transition of all elements into one another, the whole process of nature, is thus to Aristotle the constant rotation of their changes. This is unsatisfactory, because neither are the individual elements comprehended nor is the remainder rounded into a whole.
As a matter of fact, Aristotle now goes on, in meteorology, to the consideration of the universal process of nature. But here we have reached his limits. Here, in the natural process, the simple determination as such—this system of progressive determination—ceases to hold good, and its whole interest is lost. For it is in the real process that these determinate conceptions always lose their signification again and become their opposite, and in it also this contingent succession is forced together and united. In determining time and motion, we certainly saw Aristotle himself uniting opposite determinations; but movement, in its true determination, must take space and time back into itself; it must represent itself as being the unity of these its real moments and in them; that is, as the realization of this ideal. But still more must the following moments, moisture, warmth, &c., themselves come back under the conception of process. But the sensuous manifestation here begins to obtain the upper hand; for the empirical has the nature of the isolated form, which is to fall out of relation. The empirical manifestation thus outstrips thought, which merely continues everywhere to stamp it as its own, but which has no longer power to permeate the manifestation, since it withdraws out of the sphere of the ideal, while it is still in the region of time, space and movement.
As regards the other side from the Philosophy of Nature, the Philosophy of Mind, we find that Aristotle has constituted in it also a separation into special sciences, in a series of works which I shall name. In the first place, his three books “On the Soul” deal partly with the abstract universal nature of the soul, though mainly in an antagonistic spirit; and even more, and in a fashion both profound and speculative, they deal with the soul’s essential nature—not with its Being, but with the determinate manner and potentiality of its energy; for this is to Aristotle the Being and essence of the soul. Thus there are several different treatises, viz.: On Sense-perception and the Sensible, On Memory and Recollection, On Sleeping and Waking, On Dreams, On Divination (μαντική) through Dreams, besides a treatise on Physiognomy; there is no empirical point of view or phenomenon, either in the natural or the spiritual world, that Aristotle has considered beneath his notice. With respect to the practical side, he in like manner devotes his attention to man in his capacity of householder, in a work on economics (οἰκονομικά); then he takes into his consideration the individual human being, in a moral treatise (ἠθικά), which is partly an inquiry into the highest good or the absolute end, and partly a dissertation on special virtues. The manner of treatment is almost invariably speculative, and sound understanding is displayed throughout. Finally, in his Politics, he gives a representation of the true constitution of a state and the different kinds of constitution, which he deals with from the empirical point of view; and in his Politics an account is given of the most important states, of which we are, however, told very little.
In Aristotle’s teaching on this subject we must not expect to find so-called metaphysics of the soul. For metaphysical handling such as this really pre-supposes the soul as a thing, and asks, for example, what sort of a thing it is, whether it is simple, and so on. Aristotle did not busy his concrete, speculative mind with abstract questions such as these, but, as already remarked, he deals rather with the manner of the soul’s activity; and though this appears in a general way as a series of progressive determinations which are not necessarily blended into a whole, each determination is yet apprehended in its own sphere with as much correctness as depth.
Aristotle (De Anima, I. 1) makes in the first place the general remark that it appears as if the soul must, on the one hand, be regarded in its freedom as independent and as separable from the body, since in thinking it is independent; and, on the other hand, since in the emotions it appears to be united with the body and not separate, it must also be looked on as being inseparable from it; for the emotions show themselves as materialized Notions (λόγοι ἔνυλοι), as material modes of what is spiritual. With this a twofold method of considering the soul, also known to Aristotle, comes into play, namely the purely rational or logical view, on the one hand, and, on the other hand, the physical or physiological; these we still see practised side by side. According to the one view, anger, for instance, is looked on as an eager desire for retaliation or the like; according to the other view it is the surging upward of the heart-blood and the warm element in man. The former is the rational, the latter the material view of anger; just as one man may define a house as a shelter against wind, rain, and other destructive agencies, while another defines it as consisting of wood and stone; that is to say, the former gives the determination and the form, or the purpose of the thing, while the latter specifies the material it is made of, and its necessary conditions.
Aristotle characterizes the nature of the soul more closely (De Anima, II. 1) by referring to the three moments of existence: “First there is matter (ὕλη), which is in itself no individual thing; secondly, the form and the universal (μορφὴ καὶ εἶδος), which give a thing individuality; thirdly, the result produced by both, in which matter is potentiality and form is energy (ἐντελέχεια);” matter thus does not exist as matter, but only implicitly. “The soul is substance, as being the form of the physical organic body which is possessed potentially of life; but its substance is energy (ἐντελέχεια), the energy of a body such as has been described” (endowed with life). “This energy appears in twofold form: either as knowledge (ἐπιστήμη) or as active observation (τὸ θεωρεῖν). But it is evident that here it is to be regarded as the former of these. For the soul is present with us both when we sleep and when we wake; waking corresponds with active observation, and sleep with possession and passivity. But knowledge is in origination prior to all else. The soul is thus the first energy of a physical but organic body.” It is in respect of this that Aristotle gives to the soul the definition of being the entelechy (supra, pp. 143, 144).
In the same chapter Aristotle comes to the question of the mutual relation of body and soul. “For this reason” (because soul is form) “we must no more ask if soul and body are one than we ask if wax and its form are one, or, in general, if matter and its forms are one. For though unity and Being are used in various senses. Being is essentially energy.” Were we, namely, to pronounce body and soul one in the same way that a house, which consists of a number of parts, or as a thing and its properties, or the subject and predicate, and so on, are called one, where both are regarded as things, materialism results. An identity such as this is an altogether abstract, and therefore a superficial and empty determination, and a term which it is a mistake to employ, for form and material do not rank equally as regards Being; identity truly worthy of the name is to be apprehended as nothing else than energy such as has been described. The only question that now arises is whether activity and the organ it employs are one; and our idea is to answer in the affirmative. The more definite explanation of this relation is to be found in the following; “The soul is substance, but only according to the Notion (κατὰ τὸν λόγον); but that is the substantial form (τὸ τί ἦν εἶναι)[96] for such and such a body. For suppose that an instrument, such as an axe, were a natural body, this form, this axehood, would be its substance, and this its form would be its soul, for if this were to be taken away from it, it would no longer be an axe, the name only would remain. But soul is not the substantial form and Notion of such a body as an axe, but of a body which has within itself the principle of movement and of rest.” The axe has not the principle of its form in itself, it does not make itself an axe, nor does its form, its Notion, in itself constitute its substance, as its activity is not through itself. “If, for instance, the eye were in itself a living thing, vision would be its soul, for vision is the reality which expresses the Notion of the eye. But the eye, as such, is only the material instrument of vision, for if vision were lost, the eye would be an eye only in name, like an eye of stone or a painted eye.” Thus to the question, What is the substance of the eye? Aristotle answers: Are the nerves, humours, tissues, its substance? On the contrary, sight itself is its substance, these material substances are only an empty name. “As this is the case in the part, so it also holds good of the body as a whole. The potentiality of life is not in any such thing as has lost its soul, but in that which still possesses it. The seed or the fruit is such and such a body potentially. Like hewing and seeing,” in the axe and the eye, “waking” in general “is activity; but the corporeal is only potentiality. But as the” living “eye is both vision and the eyeball” (the two being connected as actuality and potentiality), “so also are soul and body the living animal, the two are not to be separated. But it is not yet clear whether the soul is the activity of the body in the same way as the steersman is of the ship.” That the active form is the true substance, while matter is so only potentially, is a true speculative Notion.
As settling the question asked in the above-mentioned metaphor, we may quote what Aristotle says later (De Anima, II. 4): “As the principle of motion and as end (οὗ ἕνεκα), and as substance of living bodies, the soul is the cause. For substance is to all objects the cause of their existence, but life is the existence of the living, and its cause and principle is the soul; and further, its energy is the existing Notion of what has potential existence. The soul is cause also as end,” that is, as self-determining universality, “for nature, like thought, acts for the sake of an object, which object is its end, but in living beings this is soul. All the parts of the body are thus the organs of the soul, and hence exist for its sake.” In like manner Aristotle shows that the soul is the cause of motion.
Aristotle (De Anima, II. 2, 3) further states that the soul is to be determined in three ways, namely as nutrient or vegetable, as sensitive, and as intelligent, corresponding with plant life, animal life and human life. The nutrient soul, when it is alone, belongs to plants; when it is at the same time capable of sense-perception, it is the animal soul; and when at once nutrient, sensitive and intelligent, it is the mind of man. Man has thus three natures united in himself; a thought which is also expressed in modern Natural Philosophy by saying that a man is also both an animal and a plant, and which is directed against the division and separation of the differences in these forms. That difference has also been revived in recent times in the observation of the organic, and it is highly important to keep these sides separate. The only question (and it is Aristotle who raises it) is how far these, as parts, are separable. As to what concerns more nearly the relation of the three souls, as they may be termed (though they are incorrectly thus distinguished), Aristotle says of them, with perfect truth, that we need look for no one soul in which all these are found, and which in a definite and simple form is conformable with any one of them. This is a profound observation, by means of which truly speculative thought marks itself out from the thought which is merely logical and formal. Similarly among figures only the triangle and the other definite figures, like the square, the parallelogram, &c., are truly anything; for what is common to them, the universal figure, is an empty thing of thought, a mere abstraction. On the other hand, the triangle is the first, the truly universal figure, which appears also in the square, &c., as the figure which can be led back to the simplest determination. Therefore, on the one hand, the triangle stands alongside of the square, pentagon, &c., as a particular figure, but—and this is Aristotle’s main contention—it is the truly universal figure. In the same way the soul must not be sought for as an abstraction, for in the animate being the nutritive and the sensitive soul are included in the intelligent, but only as its object or its potentiality; similarly, the nutritive soul, which constitutes the nature of plants, is also present in the sensitive soul, but likewise only as being implicit in it, or as the universal. Or the lower soul inheres only in the higher, as a predicate in a subject: and this mere ideal is not to be ranked very high, as is indeed the case in formal thought; that which is for itself is, on the contrary, the never-ceasing return into itself, to which actuality belongs. We can determine these expressions even more particularly. For if we speak of soul and body, we term the corporeal the objective and the soul the subjective; and the misfortune of nature is just this, that it is objective, that is, it is the Notion only implicitly, and not explicitly. In the natural there is, no doubt, a certain activity, but again this whole sphere is only the objective, the implicit element in one higher. As, moreover, the implicit in its sphere appears as a reality for the development of the Idea, it has two sides; the universal is already itself an actual, as, for example, the vegetative soul. Aristotle’s meaning is therefore this: an empty universal is that which does not itself exist, or is not itself species. All that is universal is in fact real, as particular, individual, existing for another. But that universal is real, in that by itself, without further change, it constitutes its first species, and when further developed it belongs, not to this, but to a higher stage. These are the general determinations which are of the greatest importance, and which, if developed, would lead to all true views of the organic, &c., since they give a correct general representation of the principle of realization.
α. The nutritive or vegetative soul is therefore, according to Aristotle (De Anima, II. 4), to be conceived as the first, which is energy, the general Notion of the soul itself, just as it is, without further determination; or, as we should say, plant life is the Notion of the organic. What Aristotle goes on to say of nourishment, for instance, whether the like is nourished by the like, or by the opposite, is of little importance. It may, however, be mentioned that Aristotle (De Anima, II. 12) says of the vegetative soul that it is related only to matter, and that only after a material manner, as when we eat and drink, but that it cannot take up into itself the forms of sensible things: we, too, ourselves in practical matters are related as particular individuals to a material existence here and now, in which our own material existence comes into activity.
β. There is more to interest us in Aristotle’s determination of sense-perception (De Anima, II. 5), as to which I shall make some further quotations. Sense-perception is in general a potentiality (we should say a receptivity), but this potentiality is also activity; it is therefore not to be conceived as mere passivity. Passivity and activity pertain to one and the same, or passivity has two senses. “On the one hand a passivity is the destruction of one state by its opposite; on the other hand, it is a preservation of what is merely potential by means of what is actual.” The one case occurs in the acquisition of knowledge, which is a passivity in so far as a change takes place from one condition (ἕξις) into an opposite condition; but there is another passivity, in which something only potentially posited is maintained, therefore knowledge is knowing in an active sense (supra, p. 182). From this Aristotle concludes: “There is one change which is privative; and another which acts on the nature and the permanent energy (ἕξις). The first change in the subject of perception (αἰσθητικοῦ) is caused by that which produces the perception; but, once produced, the perception is possessed as knowledge (επιστήμη).” Because that which produces the change is different from the result, perception is passivity; but it is just as much spontaneity, “and sense-perception, like knowledge (θεωρεῖν), has to do with this aspect of activity. But the difference is, that what causes the perception is external. The cause of this is that perceptive activity is directed on the particular, while knowledge has as its object the universal; but the universal is, to a certain extent, in the soul itself as its substance. Everyone can therefore think when he will,” and for this very reason thought is free, “but perception does not depend on him, having the necessary condition that the object perceived be present.” The influence from without, as a passivity, comes therefore first; but there follows the activity of making this passive content one’s own. This is doubtless the correct point from which to view perception, whatever be the manner of further development preferred, subjective idealism, or any other way. For it is a matter of perfect indifference whether we find ourselves subjectively or objectively determined; in both there is contained the moment of passivity, by which the perception comes to pass. The monad of Leibnitz appears, it is true, to be an idea opposed to this, since every monad, every point of my finger, as atom or individual, is an entire universe, the whole of which develops in itself without reference to other monads. Here seems to be asserted the highest idealistic freedom, but it is of no avail to imagine that all in me develops out of me; for we must always recollect that what is thus developed in me is passive, and not free. With this moment of passivity Aristotle does not fall short of idealism; sensation is always in one aspect passive. That is, however, a false idealism which thinks that the passivity and spontaneity of the mind depend on whether the determination given is from within or from without, as if there were freedom in sense-perception, whereas it is itself a sphere of limitation. It is one thing when the matter—whether it be sensation, light, colour, seeing or hearing—is apprehended from the Idea, for it is then shown that it comes to pass from the self-determination of the Idea. But it is different when, in so far as I exist as an individual subject, the Idea exists in me as this particular individual; there we have the standpoint of finitude established, and therefore of passivity. Thus there need be no standing on ceremony with sense-perception, nor can a system of idealism be based on the theory that nothing comes to us from without: as Fichte’s theory about himself was, that when he put on his coat, he constituted it in part by drawing it on, or even by looking at it. The individual element in sensation is the sphere of the individuality of consciousness; it is present therein in the form of one thing as much as of another, and its individuality consists in this fact, that other things exist for it. Aristotle continues: “Speaking generally, the difference is that potentiality is twofold; as we say a boy may become a general, and a grown man may also become so,” for the latter has the effective power. “This is the nature of the faculty of sense-perception (αἰσθητικόν); it is in potentiality what the object of sense (αἰσθητόν) is in actuality. Sense-perception is therefore passive, in so far as it does not resemble its object, but after the impression has been made it becomes similar to its object, and is identified with it.” The reaction of sense-perception consists therefore in this active receiving into itself of that which is perceived; but this is simply activity in passivity, the spontaneity which abrogates the receptivity in sense-perception. Sense-perception, as made like to itself, has, while appearing to be brought to pass by means of an influence working on it, brought to pass the identity of itself and its object. If then subjective idealism declares that there are no external things, that they are but a determination of our self, this must be admitted in respect to pure sense-perception, since sense-perception is a subjective existence or state in me, which yet, however, is not for that reason freedom.
In speaking of sense-perception, Aristotle (De Anima, II. 12) makes use of his celebrated simile, which has so often occasioned misapprehension, because it has been understood quite incorrectly. His words are: “Sense-perception is the receiving of sensible forms without matter, as wax receives only the impress of the golden signet ring, not the gold itself, but merely its form.” For the form is the object as universal; and theoretically we are in the position, not of the individual and sensuous, but of the universal. The case is different with us in our practical relations, where the influence working upon us pre-supposes in return the contact of the material, for which reason, as Aristotle asserts, plants do not perceive (supra, p. 186). On the other hand, in receiving form, the material is lost sight of; for the receiving of form indicates no positive relation to the matter, which is no longer something offering resistance. If, therefore, sense-perceptions are termed in general sensuous impressions, we, in matter-of-fact fashion, do not get beyond this crude way of putting it; and in making the transition to soul, we take refuge behind popular conceptions, which are partly ill-defined Notions, and partly not Notions at all. Thus it is said that all sense-perceptions are impressed on the soul by external things, just as the matter of the signet ring works on the matter of the wax; and then we hear it alleged that this is Aristotle’s philosophy. It is the same with most other philosophers; if they give any sort of illustration that appeals to the senses, everyone can understand it, and everyone takes the content of the comparison in its full extent: as if all that is contained in this sensuous relationship should also hold good of the spiritual. No great importance is therefore to be attached to this conception, as it is only an illustration, professing to show by a side comparison that the passive element in sense-perception is in its passivity for pure form only; this form alone is taken up into the percipient subject, and finds a place in the soul. It does not, however, remain in the same relation to it as that in which the form stands to the wax, nor is it as in chemistry where one element is permeated by another as regards its matter. The chief circumstance, therefore, and that which constitutes the difference between this illustration and the condition of the soul is altogether overlooked. That is to say, the wax does not, indeed, take in the form, for the impression remains on it as external figure and contour, without being a form of its real Being; if it were to become such, it would cease to be wax; therefore, because in the illustration there is lacking this reception of form into the Being, no thought is given to it. The soul, on the contrary, assimilates this form into its own substance, and for the very reason, that the soul is in itself, to a certain extent, the sum of all that is perceived by the senses (infra, p. 198): as it was said above (p. 183), if the axe had its form in the determination of substance, this form would be the soul of the axe. The illustration of the wax has reference to nothing but the fact that only the form comes to the soul; and has nothing to do with the form being external to the wax and remaining so, or with the soul having, like wax, no independent form. The soul is by no means said to be passive wax and to receive its determinations from without; but Aristotle, as we shall soon see (p. 194), really says that the spirit repels matter from itself, and maintains itself against it, having relation only to form. In sense-perception the soul is certainly passive, but the manner in which it receives is not like that of the wax, being just as truly activity of the soul; for after the perceptive faculty has received the impression, it abrogates the passivity, and remains thenceforth free from it (supra, p. 187). The soul therefore changes the form of the external body into its own, and is identical with an abstract quality such as this, for the sole reason that it itself is this universal form.