COMMENTARY ON ARISTOTLE’S
DE ANIMA

ST. THOMAS’S COMMENTARY

LECTIO ONE

§ 1. in studying any class of things, it is first of all necessary, as the Philosopher says in the De Animalibus [I, 5], to consider separately what is common to the class as a whole, and afterwards what is proper to particular members of the class. Such is Aristotle’s method in First Philosophy; for at the beginning of the Metaphysics he investigates the common properties of being as such, and only then does he go on to the particular kinds of being. The reason for this procedure is that it saves frequent repetition.

Now living beings taken all together form a certain class of being; hence in studying them the first thing to do is to consider what living things have in common, and afterwards what each has peculiar to itself. What they have in common is a life-principle or soul; in this they are all alike. In conveying knowledge, therefore, about living things one must first convey it about the soul as that which is common to them all. Thus when Aristotle sets out to treat of living things, he begins with the soul; after which, in subsequent books, he defines the properties of particular living beings.

§ 2. In the present treatise on the soul we find, first, an Introduction: in which the author does the three things that should be done in any Introduction. For in writing an Introduction one has three objects in view: first, to gain the reader’s good will; secondly, to dispose him to learn; thirdly, to win his attention. The first object one achieves by showing the reader the value of the knowledge in question; the second by explaining the plan and divisions of the treatise; the third by warning him of its difficulties. And all this Aristotle does here. First, he points out the high value of the science he is introducing. Secondly, at ‘We seek then,’ he explains the plan of the treatise. Thirdly, at ‘To ascertain anything reliable’ he warns of its difficulty. Under the first point he explains, first the dignity of this science, and then, at ‘Indeed, an acquaintance,’ its utility.

§ 3. As regards, then, the said dignity we should note that, while all knowledge is good and even honourable, one science can surpass another in this respect. All knowledge is obviously good because the good of anything is that which belongs to the fulness of being which all things seek after and desire; and man as man reaches fulness of being through knowledge. Now of good things some are just valuable, namely, those which are useful in view of some end—as we value a good horse because it runs well; whilst other good things are also honourable: namely, those that exist for their own sake; for we give honour to ends, not means. Of the sciences some are practical, others speculative; the difference being that the former are for the sake of some work to be done, while the latter arc for their own sake. The speculative sciences are therefore honourable as well as good, but the practical are only valuable. Every speculative science is both good and honourable.

§ 4. Yet even among the speculative sciences there are degrees of goodness and honourableness. Every science is valued first of all as a kind of activity, and the worth of any activity is reckoned in two ways: from its object and from its mode or quality. Thus building is a better activity than bed-making because its object is better. But where the activities are the same in kind, and result in the same thing, the quality ‘alone makes a difference; if a building is better built it will be a better building. Considering then science, or its activity, from the point of view of the object, that science is nobler which is concerned with better and nobler things; but from the point of view of mode or quality, the nobler science is that which is more certain. One science, then, is reckoned nobler than another, either because it concerns better and nobler objects or because it is more certain.

§ 5. Now there is this difference between sciences, that some excel in certainty and yet are concerned with inferior objects, while others with higher and better objects are nevertheless less certain. All the same, that science is the better which is about things; because, as the Philosopher observes in Book XI of the De Animalibus, we have a greater desire for even a little knowledge of noble and exalted things—even for a conjectural and probable sort of knowledge—than for a great and certain knowledge of inferior things. For the former is noble in itself and essential, but the latter only through its quality or mode.

§ 6. Now this science of the soul has both merits. It has certainty; for everyone knows by experience that he has a soul which is his life-principle. Also it has a high degree of nobility; for among lower things the soul has a special nobility. This is what Aristotle means here when he says, ‘Holding as we do that knowledge’, i.e. speculative science, ‘is good and honourable.’ And one science is better and nobler than another in two ways: either, as we have seen, because it is more certain—hence he says ‘more certain’,—or because it is about ‘more excellent’ things, i.e. things that are good in themselves, and ‘more wonderful things’, i.e. things whose cause is unknown. ‘For both these reasons’, he goes on to say, ‘we give a primary place to an enquiry about the soul’. He uses the term ‘enquiry’ because he is going to discuss the soul in a general way, without attempting, in this treatise, a thorough examination of all its properties. As to the words ‘a primary place’, if they are taken as applying to the whole of Natural Science, then they refer to superiority in dignity and not to priority in order; but if they refer to the science of living things only, they mean priority of order.

§ 7. Then, with ‘Indeed an acquaintance etc.,’ he gains the reader’s good will by showing the utility of this science. Some knowledge of the soul he says, would seem to be very useful in all the other sciences. it can be of considerable service to philosophy in general. In First Philosophy it is impossible to attain knowledge of the divine and highest causes except through what we can acquire by actualising our intellectual power; and if we knew nothing about the nature of this power we should know nothing about the immaterial substances, as the Commentator remarks à propos of Book XI of the Metaphysics. Again, as regards Moral Philosophy. We cannot master the science of morals unless we know the powers of the soul; thus in the Ethics the Philosopher assigns the virtues to the different powers. So, too, it is useful for the Natural Scientist, because many of the things he studies are animate things, all of whose movements originate in the soul: ‘for it is,’ says Aristotle, ‘as it were, the principle of living things’: the phrase ‘as it were’ does not express a comparison; it is descriptive.

§ 8. Next, at ‘We seek then’, he states the plan of his treatise, saying that we are ‘to consider’, i.e. by way of outward symptoms, and ‘to understand’, i.e. by way of demonstration, what the soul really is in its nature and essence; and then whatever qualities belong to it or affect it. But in the latter a diversity appears: for while some of the soul’s modifications, such as understanding and speculative knowledge, seem to belong to the soul of and in itself, others, such as pleasure and pain, the senses and imagination, though they depend on some soul or other, seem to be common to all animals.

§ 9. Then at ‘To ascertain’, he introduces the difficulty of this study; and this from two points of view. It is hard, first, to know the essence of the soul, and secondly to know its accidents or characteristic qualities. As to the essence, there is a double difficulty: first, as to how it ought to be defined, and then as to the elements of the definition (this point comes at ‘Perhaps the first thing needed’).

He remarks, therefore, that while knowledge of the soul would be valuable, it is not easy to know just what the soul is. Now this is a difficulty in studying anything; for the question about substance and essence is common to the study of soul and of many other things; the first difficulty being that we do not know what method to use; for some say we should use deductive demonstration, others the method of elimination, others one of comparison. Aristotle himself preferred the method of comparison.

§ 10. The second difficulty concerns the elements of the definition. A definition manifests a thing’s essence; and this cannot be grasped apart from the principles on which it depends. But different things have different principles, and it is hard to see which principle is involved in any particular thing. Hence, in formulating or seeking for a definition of soul we encounter three main difficulties: (a) concerning its essence; (b) concerning its parts; (c) concerning that necessary contribution to a definition which comes from knowing the soul’s accidental qualities.

§ 11. As regards the essence of soul, there is a doubt about that which is the first thing to be looked for in defining anything, i.e. the genus to which it belongs. What is the genus of soul? Is it a substance or a quantity or a quality? And not only must we decide upon the ultimate genus, but also on the proximate one; thus we do not define man as a substance, but as an animal. And if soul is found to belong to the genus of substance we shall still have to decide whether it is actual or potential substance, since every genus can be regarded both as potential and as actual. Also, since substances are either composite or simple, we shall have to ask which is one or the other and whether it is divisible or indivisible. There is also the question whether all souls are of the same species or not; and if they are not, whether they are generically different or not. Again there is uncertainty as to what is to be included in the definition, some things being defined in terms of genus, some as species; hence the question whether we should define soul in terms of genus or as the specification of a species.,

§ 12. For some enquirers seem to have in view only the human soul. Among the earlier philosophers there were two opinions about soul. The Platonists, holding that universals existed separately as the Forms or Ideas that caused knowledge and being in individual things, maintained that there was a Soul-in-Itself which was the cause aud ‘idea’ of particular souls and from which all that we find in these drew its origin. On the other hand were the Natural Philosophers who maintained that no universal substances existed in the real world, that the only real things were individuals. And this raises the question for us, whether we, like the Platonists, ought to look for one common idea of Soul; or rather, as the Natural Philosophers said, study this or that particular soul, e.g. of horse or man, or god. He says ‘or god’ because at that time men believed that the heavenly bodies were gods, and that they were alive.

§ 13. However, Aristotle chose to seek a definition of both—of Soul in general and of each kind of soul. But when he says, on this point, that ‘animal as universal is nothing real, or is secondary’, we must understand that one can speak of a ‘universal animal’ in two ways: either as universal, i.e. as one nature existing in, or predicated of, many individuals; or as animal. And both these aspects can be regarded either in relation to existence in the real world or as existing in the mind. As regards existence in the real, world, Plato held that the universal animal did so exist and existed prior to particular animals; because, as has been said, he thought that there were universals and ideas with an independent existence. Aristotle, however, said that the universal as such had no real existence, and that if it was anything at all it came after the individual thing. But if we regard the nature of animals from a different point of view, i.e. not as a universal, then it is indeed something real, and it precedes the individual animal as the potential precedes the actual.

§ 14. Then, at ‘Further, if there are not many’, Aristotle touches on the difficulties that arise concerning the soul’s potentialities. For, in, the soul are ‘parts’ that exist as potencies: the intellectual and sensitive and vegetative ‘parts’. The question is whether these are different souls, as the Platonists liked to think (and even maintained), or are only potencies in the soul. And if they are potencies, we must further decide whether to enquire first into the potencies themselves, and then into their acts, or into the acts first and then the potencies—e.g. into the act of understanding before the intellect. And if we take the acts first, there is still the question whether the objects of these acts should be studied before the faculties, e.g. the sense-object before the sense-faculty or the thing understood before the understanding.

§ 15. Next, at ‘Now it seems’, he states the difficulties that arise with regard to those accidental qualities which contribute to a definition of the soul. These are relevant here because a definition ought to reveal a thing’s accidental qualities, as well as its essential principles. If indeed the latter could be known and correctly defined there would be no need, to define the former; but since the essential principles of things are hidden from us we are compelled to make use of accidental differences as indications of what is essential. Thus to be two-footed is not of the essence of anything, yet it helps to indicate an essence. By such accidental differences we are led towards knowledge of the essential ones. It would indeed be easier to grasp even What is accidental to the soul if we could only first understand its essence, just, as in mathematics, it is a great help towards understanding that the angles of a triangle are equal to (two) right angles to know first what is meant by straight, curved and plane. Hence the difficulty of our present position. On the other hand a prior examination of the accidental factors is a considerable help towards knowing the essence, as has been said. if, therefore, one were to propose a definition from which no knowledge of the accidental attributes of the defined thing could be derived, such a definition would not be real, but abstract and hypothetical. But one from which a knowledge of the accidents flows is a real definition, based on what is proper and essential to the thing.

TEXT

403a 2-403 b 23

BOOK I, CHAPTER, I, CONTINUED

INTRODUCTION CONTINUED

QUESTIONS OF METHOD

The modifications of the soul present a problem: are they all shared by what has soul, or are some proper to the soul alone? § 16

It is necessary indeed, but not easy, to deal with this problem. For in most cases there is, apparently, no action or being acted on without the body; as in anger, desire, confidence, and sensation in general. Understanding however would seem especially proper to the soul. Yet if this too is a sort of imagination, or never occurs without it, not even this exists, in fact, apart from the body. § 17-20

But if the soul has some operation or affection exclusive to itself, then it could exist as a separate entity. If, however, there is nothing thus proper to it, then it is not separable, but is like a straight line, which has, as such, many properties—such as being able to touch a bronze sphere at a given point; but straightness separated does not touch it; not being in fact separable, since it is always with a bodily subject. § 21

Now all the soul’s modifications do seem to involve the body—anger, meekness, fear, compassion, and joy and love and hate. For along with these the body also is to some degree affected. An indication of this is that sometimes violent and unmistakable occurrences arouse no excitement or alarm; while at other times one is moved by slight and trifling matters, when the physical system is stimulated to the condition appropriate to anger. This is still more evident fearful being present, feelings occur as in one when, nothing who is frightened. If this is the case, it is evident that the passions are material principles; hence such terms as ‘becoming angry’ mean a motion of such and such a body, or of a part or power proceeding from and existing for the body. § 22

For this reason, therefore, the natural scientist ought to examine the soul, either all kinds, or this kind. § 23

The natural scientist and the dialectician will define each of those modifications differently. Take the question, what is anger? The latter will say, a desire for retaliation, or something similar; the former, an effervescence of blood or heat about the heart. Of these, the natural scientist designates the matter, the dialectician, the form or idea. For this ‘idea’ is the thing’s form. This however must have existence in material of the sort in question; if it is a house, one formula will be, ‘a covering to prevent destruction from wind and rain and excessive heat’; the other, ‘stones and beams and timber’; another, ‘the form; in these materials; for those reasons. Which is the physical definition? That which states the matter ans ignores the idea? Or that which states. the idea only?

Or rather, the compound of both? What then of the other two? Now there is no one who deals with inseparable qualities of matter, precisely as inseparable from it; but he who is concerned with the affections and activities of the special matter of this or that body is the natural scientist; whereas whatever things are not specifically such, another considers; in certain matters it may perchance be a technical expert, a carpenter or physician. Concerning however what is inseparable from matter, and yet as not involved in the specific qualities of this or that body, but abstracted from any, the mathematician; and concerning what is separable, the ‘first philosopher’. § 24-9

To return from our digression. We were saying that the passions, of the soul are not separable from the physical material of animals (anger and fear having this kind of existence), and yet also that they differ, in this, from the line and the surface.

CHAPTER II

Investigating the soul, it is necessary, while suspending judgment on matters which should be held uncertain, that we study the opinions of certain thinkers who have dealt with the subject, so as to take note of anything they said pertinently, whilst avoiding their mistakes. § 30

ST. THOMAS’S COMMENTARY

LECTIO TWO

§ 16. Having stated the difficulty of this science in respect of the problem of the soul’s substance and essence, the Philosopher proceeds to the problem of its modifications and accidental qualities. And here he does two things: he states, first, and solves a difficulty concerning the soul’s modifications; and then, using this solution, ‘he shows that knowledge of the soul pertains to natural science or ‘physics’, where he says, ‘For this reason, therefore, the natural scientist’. As to the first point, he says it is a problem whether the soul’s modifications and activities belong to it independently of the body, as Plato thought, or are none of them peculiar to the soul, being all shared by soul and body together.

§ 17. Going on at ‘It is necessary,’ he again does two things. First he shows the difficulty of the question, and then, at ‘But if the Soul,’ the necessity of putting it. He begins then by observing that we cannot avoid the question whether the soul’s modes and activities ire proper to it or shared by the body, and that this is not an easy question but a very difficult one. The difficulty, as he explains, arises from the fact that many activities seem to be common to soul and body and to require the body, for instance, getting angry and having sensations and so on; which all involve body as well as soul. If there is anything peculiar to the soul it would appear to be the intellectual activity or understanding; this seems to belong to the soul in a special way.

§ 18. And yet, on closer consideration, even understanding would not seem to pertain to the soul alone. For either it is the same as imagination, as the Platonists thought, or it does not occur without the use of imagination (for there used to be men, such as the early natural philosophers, who said that intellect in no way differed from the senses, which would imply that it does not differ from the imagination; as indeed the Platonists were led to say). As, then, imagination presupposes the body and depends on it, they said that understanding was common to soul and body together, rather than the work of the soul alone. And even granted that intellect and imagination are not identical, still the one cannot function without the other. It would follow that understanding is not of the soul alone, since imagining presupposes the body. Understanding then, it seems, does not occur where there is no body.

§ 19. Now although Aristotle clears up this problem in Book III, we shall say something about it here. Understanding, then, is in one sense, proper to the soul alone, and in another sense common to both soul and body. For it should be realised that certain activities or modifications of the soul depend on the body both as an instrument and as an object. Sight, for instance, needs a body as object—because its object is colour, which is only found in bodies;—and also as an instrument—because, while the act of seeing involves the soul, it cannot occur except through the instrumentality of a visual organ, the pupil of the eye. Sight then is the act of the organ as well as of the soul. But there is one activity which only depends on the body to provide its object, not its instrument; for understanding is not accomplished with a bodily organ, though it does bear on a bodily object; because, as will be shown later, in Book III, the phantasms in the imagination are to the intellect as colours to sight: as colours provide sight with its object, so do the phantasms serve the intellect. Since then there cannot be phantasms without a body, it seems that understanding presupposes a body-not, however, as its instrument, but simply as its object.

§ 20. Two things follow from this. (1) Understanding is an act proper to the soul alone, needing the body, as was said above, only to provide its object; whereas seeing and various other functions involve the compound of soul and body together. (2) Whatever operates of itself independently, has also an independent being and subsistence of its own; which is not the case where the operation is not independent. Intellect then is a self-subsistent actuality, whereas the other faculties are actualities existing in matter. And the difficulty in dealing with this type of question arises simply from the fact that all functions of the soul seem at first sight to be also functions of the body.

§ 21. After this, when Aristotle says ‘But if the soul’, he states a reason for putting this question, namely, that on its answer depends the answer to a question that everyone asks very eagerly about the soul: whether it can be separated from the body. So he says that if the soul has any function proper to itself it can certainly be separated, because, as was pointed out above, whatever can operate on ,its own can exist on its own. Conversely, if the soul had no such proper function it would not be separable from the body; it would be in the same case as a straight line—for though many things can happen to a straight line qua straight line, such as touching a brass sphere at a certain point, still they can only come about in a material way: a straight line cannot touch a brass sphere at any point except materially. So also with the soul; if it has no activity proper to itself, then, however many things affect it, they win do so only in a material way.

§ 22. Next, when he says ‘Now all the soul’s,’ he draws out what had been presupposed above, namely that certain modifications affect soul and body together, not the soul alone. And this he shows by one argument in two parts; which runs as follows. Whenever the physical constitution of the body contributes to a vital activity, the latter pertains to the body as well as the soul; but this happens in the case of all the ‘modifications’ of the soul, such as anger, meekness, fear, confidence, pity and so forth, hence all these ‘modifications’ would seem to belong partly to the body. And to show that the physical constitution plays a part in them he uses two arguments. (1) We sometimes see a man beset by obvious and severe afflictions without being provoked or frightened, whereas when he is already excited by violent passions arising from his bodily disposition, he is disturbed by mere trifles and behaves as though he were really angry. (2) At ‘This is still more evident:’ what makes this point even clearer is that we see in some people, even when there is no danger present, passions arising that resemble one such ‘modification’ of the soul; for instance melancholy people, simply as a result of their physical state, are often timid when there is no real cause to be. Obviously then, if the bodily constitution has this effect on the passions, the latter must be ‘material principles’, i.e. must exist in matter. This is why ‘such terms,’ i.e. the definitions of these passions, are not to be predicated without reference to matter; so that if anger is being defined, let it be called a movement ‘of some body’ such as the heart, or ‘of some part or power’ of the body. Saying this he refers to the subject or material cause of the passion; whereas ‘proceeding from’ refers to the efficient cause; and ‘existing for’ to the final cause.

§ 23. Then at ‘For this reason,’ he concludes from the foregoing that the study of the soul pertains to natural science—a conclusion following from the way the soul is defined. So he does two things here: (1) he proves his statement; (2) he pursues his discussion of definitions, where he says ‘the natural scientist and the dialectician’. The proof of his statement runs thus. Activities and dispositions of the soul are also activities and dispositions of the body, as has been shown. But the definition of any disposition must include that which is disposed; for its subject always falls within the definition of a disposition. If, then, dispositions of this kind are in the body as well as in the soul, the former must be included in their definition. And since everything bodily or material falls within the scope of natural science, so also must the dispositions of which we speak. Moreover, since the subject of any dispositions enters into the study of them, it must be the task of the natural scientist to study the soul—either absolutely ‘all’ souls, or ‘of this kind’, i.e. the soul that is joined to a body. He adds this because he has left it uncertain whether intellect is joined to the body.

§ 24. Where he says ‘The natural scientist and the dialectician,’ he continues his discussion of definitions. Explaining that, while some definitions of the dispositions of the soul include matter and the body, others exclude matter and refer only to the form, he shows that the latter kind of definition is inadequate. This leads him to go into the difference between these types of definition. Sometimes the body is omitted, as when anger is defined as a desire of revenge; and sometimes the bodily or material factor is included, as when anger is called a heating of blood round the heart. The former is a logical definition, but the latter is physical, since it includes a material factor, and so pertains to the natural scientist. The natural scientist points to the material factor when he says that anger is a heating of blood round the heart; whereas the dialectician points to the species or formal principle; since to call anger a desire of revenge is to state its formal principle.

§ 25. Now the first type of definition is obviously inadequate. The definition of any form existing in a particular matter must take account of the matter. This form, ‘the desire for retaliation’, exists in a definite matter, and if the matter is not included, the definition is clearly inadequate. The definition, then, must state that this thing, i.e. the form, has being in this particular sort of matter.

§ 26. Thus we have three kinds of definition. The first states the species and specific principle of a thing, and is purely formal—as if one were to define a house as a shelter from wind, rain and heat. The second kind indicates the matter, as when a house is called a shelter made of stones and beams and wood. But the third kind includes in the definition ‘both’, namely matter and form, calling a house a particular kind of shelter, built of particular materials, for a particular purpose—to keep out the wind, etc. So he says that ‘another’ definition has three elements: the material, ‘in these’, i.e. beams and stones; the formal,”the form’; and the final, ‘for those reasons’, i.e. to keep out the wind. So matter is included when he says ‘in these’. form when he says ‘form’. and the final cause when he says ‘for those reasons’. All three are needed for a perfect definition.

§ 27. To the question which of these types of definition pertains to the natural scientist, I answer that the purely formal one is not physical but logical. That which includes matter but omits the form pertains to no one but the natural scientist, because only he is concerned with matter. Yet that which includes both factors is also in a special way the natural scientist’s. Thus two of these definitions pertain to natural science, but of the two the merely material one is imperfect, while the other, that includes the form also, is perfect. For only the natural scientist studies the inseparable dispositions of matter.

§ 28. But there are various ways of studying the dispositions of matter, as Aristotle now proceeds to show. He divides the students of these dispositions into three classes. One class consists of those who, while they study material dispositions, differ from the natural scientist in their point of view; thus the craftsman differs from the scientist in that he starts from the point of view of art, but the natural scientist from that of real nature. Another class consists of those who, though they consider forms that exist in sense-perceptible matter, do not include such matter in their definitions. The forms referred to are such as curved, straight, and so on, which, though they exist in matter and are, in fact, inseparable from it, are not, by the mathematician, regarded under their sense-perceptible aspect. The reason is that if it is through its quality that a thing is sense-perceptible, quality presupposes quantity; hence the mathematician abstracts from this or that particular material factor in order to attend exclusively to the purely quantitative. Finally, the third class studies things whose existence is either completely independent of matter or can be found without matter. This is First Philosophy.

§ 29. Note that this division of Philosophy is entirely based on definition and the method of defining. The reason is that definition is the principle of demonstration. Since things are defined by their essential principles, diverse definitions reveal a diversity of essential principles; and this implies a diversity of sciences.

§ 30. Then at ‘To return,” he comes back to the matter in hand after the apparent digression about definitions. The point under discussion was that such modifications of the soul as love, fear and so forth are inseparable from physical animal matter inasmuch as they have this sort of existence, i.e. as passions in the body; in which they differ from lines, plane-surfaces and so on, which can be considered by the mind apart from the matter that they naturally imply. If this is the case then the study of such dispositions, and even of the soul itself, becomes, as has been said, the affair of the natural scientist.

And ‘concerning this’ i.e. the soul, we must, at our present stage, take account of the opinions of the ancients no matter who they were, provided they had anything to say about it. This win be useful in two ways. First, we shall profit by what is sound in their views. Secondly, we shall be put on our guard against their errors.

TEXT

403b24–404b7

BOOK I, CHAPTER II, CONTINUED

PREVIOUS THEORIES

DEMOCRITUS, THE PYTHAGOREANS, ANAXAGORAS

Our enquiry must begin with a statement of what seems most to belong by nature to the soul. The animated being would appear to differ from the inanimate in two primary respects: by motion and by sense-perception. And these two notions are roughly what our predecessors have handed down to us concerning the soul. § 31-2

For some say that the soul is principally and primarily what moves. Holding that what does not itself move moves no other moving thing, they thought that the soul too was thus. § 33

Hence Democritus, said it was a kind of fire or heat. There exist an infinite number of shapes and atoms, and those of the spherical kind are, he said, fire and soul: like the dust-motes in the air called ‘atomies’ seen in the rays of the sun in doorways; and of all the seeds of these, he said, are the elements of all Nature. Leucippus had a similar opinion. Those round in shape make the soul, because they are most able to penetrate everywhere, and since they move of themselves, they have also the power to move everything else. The soul, they maintained, is what causes movement in living things: and accordingly breathing is coterminous with living. That which envelops all bodies expels by compression the atoms [within], thus causing movement in animals, for these [atoms] are never at rest. A reinforcement must come therefore [he said] from without; in that other atoms enter by respiration, preventing from dispersal those that are within the animate body, and which simultaneously resist the constraining and compressing environment; and that animals live so long as they can do this. § 34-5

The teaching of the Pythagoreans seems to have had much the same purport. Some of these said the soul consisted of atoms in the air; others, that it was what sets these in motion. And these atoms are mentioned. because they seem to be always moving, even if the soul be quite tranquil. § 36

All who say that the soul is a thing that moves itself tend in the same direction; all seem to hold that movement is what is most proper to the soul, and accordingly that all things are in motion on account of the soul, but the soul itself on its own account; because one sees nothing moving other things that is not itself moving. § 37

Anaxagoras likewise said that the soul is a mover, as also did anyone else who held that a Mind moves all things. But his view is not exactly Democritus’. § 38

He [Democritus], asserts that intellect and soul are absolutely identical; and that what appears is the truth. And therefore that Homer aptly says of Hector that he lay ‘other-minded’. He does not use the term intellect to denote a definite faculty concerned with truth, but identifies soul and intellect. § 39

Anaxagoras is less definite about these matters. He often says that the cause of being right or good is intellect, and that this is the soul. For it is, he says, in all animals, great and small, noble and base. § 40

It does not seem, however, that there exists mind, in the sense of prudence, alike in all animals: nor even in all men. § 41

All those therefore who have regarded life from the point of view of movement have held soul to be pre-eminently a moving force. § 42

ST. THOMAS’S COMMENTARY

LECTIO THREE

§ 31. So much by way of Introduction. The Philosopher has stated his aim in general and the difficulty of the undertaking; which he now proceeds to carry out in the order already indicated. The whole treatise divides into two parts. In the first the soul’s nature is discussed as other philosophers have regarded it; but in the second as it is in reality. The latter section begins at Book II. The first part itself has two parts. The former simply relates the opinions of other philosophers; the second, beginning at ‘The first thing to be considered,’examines them. The former part itself divides into two parts, in the first of which Aristotle distinguishes

between the starting points of the other philosophers, while in the second, starting at ‘For some say’, he shows how they severally came to hold their different opinions.

§ 32. First of all then he says that one ought to start by gathering together everything that would seem to belong to the soul by nature. As to this, we should note that when we find things differing both by clear and understandable differences and by differences that are still obscure, we must assuredly take the former as a means to arrive at knowledge of the latter. This was the method used by the philosophers in their study of the soul. Living things differ from non-living in having ‘souls’; but because the nature of the soul was not evident and could not be investigated except by way of certain more obvious notes which differentiate animate from inanimate things, the philosophers first took these more evident characteristics and tried, through them, to come to knowledge of the soul’s nature. These evident notes are two: sensation and movement. Animate things seem to be characterised chiefly by movement, in that they move themselves, and by having sense awareness or perception. So the ancients thought that if they could discover the principle of these two factors they would know the soul; hence their efforts to discern the cause of movement and sensation. They all agreed in identifying the soul with the cause of movement and sense-perception. But just at this point also their differences began; for some tried to arrive at the soul by way of movement, and others by way of sense-perception.

§ 33. Hence at ‘For some say’ he states these differences: taking those of his predecessors first who started their enquiry from movement; and then, at ‘All who have considered’, those who started from knowledge; and thirdly, at ‘But since the soul’, those who started from both. With regard to the first group we should note that it had one principle in common, namely, that if living things are moving things, the soul must be both moving and moved. They assumed this because they, thought that one thing could only move another if it were itself already moved; that is, only what is moved moves. So if living things are moved, by the soul, then clearly the soul itself, and preeminently, must be moved. It was this that led the early students of Nature to class the soul among things that are moved. But about this also different opinions arose.

§ 34. When therefore he says, ‘Hence Democritus’, Aristotle states first of all the view of Democritus, one of the early philosophers, who, thinking that the soul by nature was in a state of maximum movement, which state seems natural to fire, maintained that the soul ‘was a kind of fire or heat’. Such was his view. For he did not admit the existence of anything in Nature except what is sense-perceptible and corporeal; and the first principles, he said, of all things are indivisible bodies, infinite in number, which he called atoms. These atoms, he said, are all the same by nature, differing from each other only in shape, position and arrangement (though here only the difference of shape is alluded to, as being the only necessary one. This consists in some being round, some square, some pyramids, and so on). He also maintained that the atoms were mobile and never ceased moving, and that the world had come into being through their fortuitous coming together. And to illustrate the mobility of these bodies he took the example of the particles that move in the air even when no wind blows, as we can see when a sunbeam shines through a doorway. Since the atoms, being indivisible, are much smaller than such particles, they must obviously be extremely mobile. And because the spherical is, of all shapes, the one best suited for movement—having no angles to impede it,—and since the soul, as the cause of movement in living was thought to have maximum mobility, Democritus concluded that among these infinitely numerous bodies the spherical ones were the soul.

135. Leucippus, a companion of Democritus, held the same opinion. And Democritus thought the following was a sign of its truth. He maintained that ‘coterminous with’, or essential to, life is respiration (a short-sighted view since not all living things breathe), and that respiration is necessary because the body is full of small ever-moving spherical particles (the cause, as he thought, of all movement in animal bodies) and that the surrounding air compresses what it ‘envelops’, i.e. our bodies, and ‘expels’, i.e. thrusts out of them, those particles which are so shaped as to impart movement to animals, being never at rest themselves. Lest, therefore, our bodies should decay with the loss of all these particles, he said that respiration is necessary whereby fresh particles may be brought in, and those already within prevented from leaving by those that inhaling brings in. And he said that animals can live as long as they can do this, i.e. as long as they can breathe. The point of the argument is that if breathing is called the cause of life because it keeps the spherical particles inside the animal body, and also introduces fresh ones lest the body should decay through loss of particles by movement, then it is clearly implied that the particles ate the soul itself. They are indeed the same particles that Democritus said were fiery by nature and the cause of heat.

§ 36. Next, at ‘The teaching of the Pythagoreans,’ Aristotle mentions a view of certain Pythagoreans which resembles that of Democritus; for their statement and his seem to mean the same’ although the Pythagoreans themselves do not all agree. Some of them, agreeing with Democritus, said that motes in the air, i.e. indivisible, infinitely numerous particles, were the soul. Others, however, of the same school, said that the soul was rather the force that moved those particles. Of this opinion was a certain Archelaus, the master of Socrates, as Augustine remarks in the De Civitate Dei [VIII, 2]. The reason why the soul has been thus identified with these particles has been already given—namely, that as the soul was regarded as being especially mobile, and as those particles seem to be always moving (even when the air is calm) they identified the one with the other.

§ 37. Then, at ‘All who say,’ he summarises the views of a number of philosophers, saying that all who have defined the soul in terms of movement and called it that which moves itself, ‘tend in the same direction’, i.e. the same as those mentioned already. All these, it seems, agreed -in thinking that the soul’s first and chief characteristic was movement; all things being moved by soul, and soul by itself. The reason for this was, as has been noted, that they all thought that only what was itself in motion could move other things. Since the soul moves other things, they thought the soul especially and principally was in motion.

§ 38. In the third place, at ‘Anaxagoras likewise’, he states the view of Anaxagoras. He first shows how this philosopher agrees with those already mentioned, saying that he, and anyone else who held that Intellect moved all things, really agreed with them that the source of all movement was a soul. Anaxagoras, however, differed in this that he denied that every mover was itself in motion, and maintained the existence of a pure and transcendent Intellect which, motionless itself, moved all other things; and that the soul was of this nature too. (This view led some into the error of divinising the soul.) Thus Anaxagoras agreed with the other philosophers in calling the soul a principle of movement, but disagreed with them in saying that it was not itself moved (for they said the contrary). And he also differed from Democritus in what he understood by intellect.

§ 39. When Aristotle therefore says ‘He (i.e. Democritus) asserts’, he states this last difference, first stating Democritus’ opinion that intellect and soul were ‘absolutely’, i.e. everywhere and in all respects, the same. Democritus said this because he held that only sense-perceptible things existed in the real world, and that no cognitive faculty existed in the soul except sensitivity. From this he inferred that no definite truth about things was attainable, that nothing could be definitely known with certainty: truth being simply what appears to be true; and what one man thought about anything being never any nearer the truth than what another man thought about the same thing at the same time. in consequence he maintained that contradictories were both true at the same time; and this because, as we have said, he took intellect to be, not the faculty for knowing truth and understanding intelligible objects, but a mere sense-faculty. Only the sensible, he thought, could be known, since only the sensible existed. And because the latter is continually changing there could be no certain truth about anything. Never attaining to an understanding of the intellect as the supreme faculty ‘concerned with truth’, i.e. which bears on true being, and admitting only the faculties of sense, he completely ‘identifies soul and intellect’. The intellect changed, he said, as the whole man changed. Hence his approval of Homer’s Phrase ‘Hector lies other-minded’, i.e. Hector’s mind was altered by Hector’s condition; for he thought one thing as conqueror, another as conquered.

§ 40. Next, at ‘Anaxagoras is less definite’, he shows how Anaxagoras differed from Democritus, first stating the former’s opinion and then, at ‘it does not seem’, criticising it. First then he observes that Anaxagoras spoke with less certainty and less conclusively about the soul. He often said that intelligence was the cause of right actions, whilst elsewhere he also identifies intelligence with the soul; for it is agreed that a soul is found in all animals, the lower as well as the higher, the smaller as well as the larger; and Anaxagoras said that intelligence was in all of them. Clearly then he identifies soul and intelligence.

§ 41. Secondly, at ‘It does not seem’, he shows the inconsistency of Anaxagoras’ use of the term intellect. For sometimes Anaxagoras distinguishes between soul and intellect, but sometimes also he identifies them. These are contradictory statements which cannot both be true; as Aristotle proceeds to show. Right action, he says, admittedly derives from intellect perfected by prudence. If then the intellect that causes right action is the same thing as the soul, it follows that intellect perfected by prudence is the same as the soul. But this is false; because, while all animals have souls, not all—not even all men—are prudent. Therefore the soul is something else.

§ 42. Lastly, at ‘All those therefore,’ he states that all who have regarded animate beings from the standpoint of movement, i.e. as self-movers, thought that the chief mover in them was the soul, as the above-mentioned opinions show.

TEXT

404 b 8-404 b 29

BOOK 1, CHAPTER II, CONTINUED

PREVIOUS THEORIES. EMPEDOCLES, PLATO, SOUL AS SELF-MOVING NUMBER

All who have considered it as knowing and perceiving realities identify the soul with the [elemental] principles,—some making several principles, others one. § 43-4

Empedocles, for instance, says that it is composed of all elements, and that each of these is a soul, saying,

As by earth we know earth, by ether divine ether,

By water water, by fire, it is clear, fire mysterious and hidden;

Love by love, hate by sad hate. §45

In the same way Plato in the Timaeus constitutes the soul from the elements. For like [he says] is known by like; and things are made up of elements. §§46-7

In the lectures ‘On Philosophy’ he likewise lays it down that the animate itself is compounded of the idea of the One, together with the primary Length and Depth and Breadth; other things existing in the same manner. § 48-50

Again, rather differently, that intellect is the One, knowledge the Two (for [this proceeds] as one to one), and the number of the Plane belongs to opinion, and that of the Solid to sensation. For he said that numbers are the specific forms and principles of beings, and are themselves constituted from elements. Some things are discerned by understanding, some by science, some by opinion, some by sensation. But these same numbers are the specific forms of things. § 51

But since the soul seems to be both a moving and a knowing principle, some have made it out to bea combination of these two, stating that it is a self-moving number. § 52

ST. THOMAS’S COMMENTARY

LECTIO FOUR

§ 43. Having shown how some have approached a knowledge of soul through movement, the Philosopher now turns to those who came to it by way of sensation or knowledge. He does this in. two stages. First he shows where the latter were in agreement; and secondly, at ‘Empedocles, for instance,’ where they disagreed.

He begins then by saying that all who studied the soul in or through its knowing and sensing agreed in holding that the soul was composed of the principles of things; but some ‘made’, i. e. posited, many such principles, while others posited only one. Even the earliest philosophers assumed these principles to be in the soul, as though compelled by the force of truth itself; they dreamed, as it were, of the truth. The truth, in fact, is that knowledge is caused by the knower containing a likeness of the thing known; for the latter must be in the knower somehow. The early philosophers, however, thought that it existed in the knower in its own natural being, i.e. with the being that it has in itself. Like, they said, must be known by like. If then the soul is to know all things it must contain a likeness of all things according to their natural mode of being. They could not distinguish between the mode of existence that a thing has in the mind or the eye or the imagination from that which it has in itself. Therefore, since whatever is of a thing’s essence is a constituent principle of the thing, and to know its constituent principles is to know the thing itself, these philosophers maintained that the reason why the soul can know all things is that it is made up of the principles of all things. This theory was common to them all.

§ 44. But they differed about these principles. They did not all admit the same; one admitted many, another only one, and one this and another that. Hence they disagreed also about the constituents of the soul.

§ 45. So, at ‘Empedocles, for instance,’ Aristotle states these differences. He gives first the opinion of Empedocles, saying that the early philosophers who studied the soul by way of its sense-perceptions thought it was composed of the elements. Those who admitted only one principle said that this precisely was the soul; and those who admitted many said that the soul was made up of many; thus Empedocles held that the soul was constituted by all the elements, and that each of these was itself a soul. Note that Empedocles admitted six principles: four material, namely earth, water, fire and air; and two active and passive principles, namely strife and friendship. And since he assumed that the soul knew all things, he said it, was composed of all these principles. Thus as earthy we know earth; as ethereal or airy we know air; as aequous we know water; and as fiery, of course, we know fire. Through love we know love, and through ‘sad hate’ we know hatred. ‘Sad’ comes in here because Empedocles wrote in verse.

§ 46. Next, when he says ‘In the same way Plato’ Aristotle states the opinion of Plato who also, he says, made the soul consist of elements, i.e. be constituted by the, principles of things. And as evidence for this statement he takes three passages from Plato. The first is from the Timaeus, where Plato says that there are two elements or first principles, Identity and Difference. For there is a certain kind of nature that is simple and unchanging, as are immaterial things; and this nature he calls Identity. And there is another kind which does not stay the same, but undergoes change and division, as do material things; and this nature he calls Difference. And it is of these two principles, of Identity and Difference, that the soul, he says, is composed; not that the two are in the soul as its parts; but rather as in the mean between extremes; for the rational soul is by nature lower and less noble than the higher and purely immaterial substances, but it is higher and nobler than inferior material things.

§ 47. Now this opinion rests on the principle already mentioned, that like is known by like. For it seemed to Plato that if the soul knew all things, and if Identity and Difference were fundamental principles, then the soul itself must be constituted of Identity and Difference; in so far as it participated in ‘Identity’ the soul, he thought, knew the ‘identical’, while so far as it participated in ‘Difference’ it knew the ‘different’, i.e. material things. Hence the actual process of the soul in knowing things. For when it gathers things together under genera and species, then, said Plato, it manifests Sameness or Identity, but when it attends to accidents and differentiations he finds in it Difference. That is how Plato in the Timaeus understood the soul as made up of principles.

§ 48. The second passage, showing that this was Plato’s theory, Aristotle refers to when he says ‘In the lectures “On Philosophy”.’ Here too the soul is represented as constituted from principles. Note, in this connection, that Plato took the objects known by the intellect to be things in themselves, existing apart from matter in perpetual actuality, and the causes of knowledge and of being in things of sense. For Aristotle this view involved so many difficulties that he was compelled to excogitate the theory of the ‘agent intellect’. But from Plato’s position it followed that to what could be thought of in the abstract corresponded subsistent and actual realities. We can, however, form abstractions in two ways: one is by proceeding from particulars to universals; and the other is that by which mathematical objects are abstracted from objects of sense. So Plato found himself obliged to posit three types of subsistent being: the objects of sense-perception; mathematical objects; and universal ideas-these last being the cause, by participation, of the other two types.

§ 49. Plato also held that numbers were causes of real things, being unaware of the distinction between unity as identical with being, and unity as the principle of the number that is a kind of quantity. Hence he inferred that universals were of the nature of number; for the universal existing separately is the cause of things whose substance is numerical. He said indeed that the constituent principles of all beings were ‘species’ and ‘specific number’, which he called specific in the sense of being constituted from ‘species’. And he reduced number itself to unity and duality as to its fundamental elements; for, as nothing can proceed from one alone, there must, he thought, be some nature, subordinate to unity, whence multiplicity might proceed; and this nature he called duality.

§ 50. Thus Plato envisaged three classes of beings, graded according to their connection with matter. As sensible objects are more material than the objects considered in mathematics, and the latter more so than the universal ideas, he placed sense-objects on the lowest level, and above them mathematical objects, and above these the separately existing universals and ideas. Universals differ from mathematical objects in this that the latter include numerical differences Within the same species, whereas ideas and separated substances exhibit no numerical differences in the one species; there is but ore idea for each species. These ideas, he said, are numerical in nature, and from them are derived such numerical qualities of sensible things as length, breadth and depth. Hence he said that the idea of length was the primary duality, for length is from unit to unit, from point to point; and that of breadth was the first trinity, for the triangle is the first of plane figures; and that of depth, which includes both length and breadth, was the first quaternity, for the first solid figure is the pyramid which is constructed of four angles. So too the sensitive soul, in Plato’s system, implied a Soul existing separately as its cause, and constituted, like the other ‘separate’ things and ideas, by number, that is, by the unity and duality which for him were fundamental in ,things.

§ 5 1. Then at ‘Again, rather differently,’ Aristotle alludes to the third text adduced to show that for Plato the soul was made up of elements or principles. As we have said, it was Plato’s view that the specific forms and, principles of things were numbers; so when he came to treat of the soul he based its knowledge of things on its fundamentally numerical composition; all of its activities, he maintained, sprang from this source. Take for instance the diverse apprehensive functionings of the soul: simple understanding, science, opinion and sensation. Simple understanding Plato connected with the idea of One; it has the nature of Unity; for in one act it apprehends a unity. Again, science for him relates to Duality since it proceeds from one to one, i.e. from principles to conclusions. And opinion relates to the first Trinity, proceeding from one to two, i.e. from principles to a conclusion which is accompanied by the fear that a different conclusion may be true; so forming a triad out of one principle and one admitted and one feared conclusion. Finally, sensation derives from the first Quaternity, i.e. from the notion of a solid body constructed (as we have said) from four angles; for bodies are the object of sensation. Since then all knowing is contained in these four, i.e. in simple understanding, science, opinion and sensation, all of which, said Plato, are in the soul in virtue of its participating in the nature of Unity, Duality, Trinity and Quaternity, it obviously follows that for Plato the separated Soul, the ‘idea’, as he called it, of particular souls, was constituted by numbers, which are the elements or principles of reality. So much to show that Plato regarded the soul as made up of principles.

§ 52. Next at ‘But since the soul seems,’ Aristotle observes that some philosophers defined the soul, and came to know something about it, through both movement and sensation or knowledge. He says that, as the soul seemed to them to be both self-moving and cognitive, they joined the two aspects in their definition and called it a ‘self-moving number’. ‘Number’ refers to the cognitive power because they thought, in accordance with what has been said already, that the soul was able to know in virtue of its participating in the nature of specific number (Plato’s opinion). ‘Self-moving’ refers to the soul’s motive power.

TEXT

404b30–405b30

BOOK I, CHAPTER, II, CONTINUED

PREVIOUS THEORIES

SOUL AS IDENTIFIED WITH THE ELEMENTS

Opinions differ however as to the elemental principles—what they are, how many they are; and the difference is greatest between those who make these corporeal and those who make them incorporeal. But some, making a mixture, have defined the principles in terms of both. They differ also as to the number, some positing one, others several. And they assign a soul to these [principles] accordingly. (For they not unreasonably assumed that what by nature causes movement was primary.) §§ 53-4

Hence some have held it to be fire; for this is the most subtle, and much the least corporeal of the elements; moreover, it moves itself, being the first cause of movement in other things. Democritus said something which rather neatly gives the reason for either fact. He said that soul is the same as mind, and that this originates in primary indivisible particles and that it causes motion by its fineness and shape. He says that the sphere is the most light and mobile of shapes, and that fire and mind must both be of such a nature. §§ 55-6

Anaxagoras, however (as we said above), seems to speak of soul and mind as diverse, yet he employs both terms as for a single essence. Nevertheless, he posits Intellect as the principle par excellence of the Universe, saying that this alone among beings is simple, unmixed and pure. He attributes, indeed, to the same principle both knowing and moving; saying that the Intellect moves all things. § 57

It seems that Thales, from what they recollect of him, was also of opinion that the soul was a cause of motion,—if it is a fact that he said that the magnet had a ‘soul’ because it attracts iron. §58

Now Diogenes, like certain others, held that air is the most subtle of all things and is their principle; and is the cause of the soul’s knowing and moving. As primary, it is cognitive of all else: and as the most subtle thing, it is the motive force. § 59

Heraclitus, however, says that soul, as a principle, is some vapour of which it is constituted, since this is the least corporeal of substances and is always flowing; and that any moving object is known by a moving object—he and many others holding that all realities are in movement. § 60

Alcmaeon seems to have held opinions on the soul similaR to these. For he said it was immortal because it. bore a resemblance to immortal beings. And this he attributed to it because it always moves; all heavenly things seem to be in motion continually—the sun, the moon, the stars, all heaven. § 61

Some cruder thinkers, like Hippo, thought it was water. They seem to have been persuaded of this because semen is liquid in all animals. For he confutes those who say the soul is the blood, on the ground that semen, which is the inchoate Soul, is not blood. § 62

Others, such as Critias, held it was blood; that sensation was most distinctive of the soul; and that it was due to the nature of blood that this power was in it.

For opinions have been given in favour of every element excepting earth: which no one has proposed, unless whosoever may have said it was derived from all the elements, or was identical with them, did so. § 64

All, taken together, define soul, we may say, by three things: by movement, by sensation, and by immateriality. And each of these is reduced to elemental principles. Hence, in defining it as cognitive, they make it either an element or consist of several elements, one saying much the same as another (with a single exception). For they say that anything is known by what resembles it, and as the soul knows all things, go they constitute it of all principles: some saying that there is one cause and one element, and that the soul is a single thing—fire or water, for example; others that there are several principles, and that the soul is multiple. § 65

But Anaxagoras, standing alone, says that mind is beyond the reach of influence and has nothing in common with other things. But, granted that this be true, he, did not explain how it acquires knowledge, in virtue of what cause; nor is this made clear by anything else he said. § 66

Those who posit contraries as first principles also maintain that the soul consists of such contraries, while those who favour some one among contraries (hot or cold, or some other like these) make the soul, accordingly, one of these. Whence also some follow names, as those who allege that it is heat, because life is due to heat and is named from it. But those who identify the soul with cold say that it is named from respiration and breathing.

Such then are the opinions that have been transmitted to us about the soul, together with the reasons given for them. § 67

ST. THOMAS’S COMMENTARY

LECTIO FIVE

§ 53. In the preceding chapters Aristotle has shown the old philosophers agreeing in their analysis of the soul, in that they all regarded it as the origin of movement and knowledge. in the section beginning now he shows how they variously interpreted that common presupposition. This section falls into three parts: in the first he shows the root of the divergence of these philosophers in their teaching on the soul; the second enumerates the various points of difference (beginning at ‘Hence some’); the third summarises all that we have to consider in these differences (at ‘All, taken together’). The root of the divergence of the philosophers in their teaching on the soul is to be looked for in the way they analysed it into its ultimate elements; as they disagreed about these elements so did they differ about the soul. They all agreed that the soul was made up of ultimate elements, but they could not agree that it was made up of the same elements; and, differing as to the elements, they differed in their theories of the soul.

§ 54. They differ in two ways about the ultimate elements: first, as to their essential nature, i.e. ‘what’ they are; secondly, as to their number, ‘how many’ they are. As regards their essential nature, some said these principles were corporeal (fire or water or air) while others said they were incorporeal and immaterial, such as those who spoke of numbers and ideas; and there were others, like the Platonists, who blended both views and allowed that there existed both sensibly perceptible and separate immaterial principles. As to their number or multiplication, there were some who admitted only one principle. Heraclitus, for instance, said it was air; and someone else, fire; while others said there were many principles—Empedocles for instance, who maintained the theory of the four elements. And their theories of the soul in respect of the elements followed these various hypotheses concerning ultimate elements. Those who held to a theory of material first principles, like Empedodes, said the soul was composed of such; and those, like Plato, who held to immaterial principles, said that the soul was composed of these. But one and all considered the soul to be the chief source of movement.

§ 55. Next, at ‘Hence some’, he proceeds to run through the more particular differences between the philosophers. it should be noted that of those who thought that a corporeal thing was the first principle, not one deigned to identify this with mere earth. Some said it was fire, others air, others water, but nobody said it was earth, except those who thought that all the four elements together were the first principle. (The reason being that, with its density, earth seemed always to presuppose some more ultimate principle). Aristotle, then, does three things here. He gives first the views of those who identified the first principle and the soul itself with fire; secondly, of those who held that they were air (at ‘Now Diogenes’); and thirdly, the opinion of those who held that water was both the first principle and the soul (beginning at: ‘Some cruder thinkers’).4

§ 56. As to the first of these groups, we should note that since movement and knowledge were ascribed to the soul, it appeared to some that the soul possessed these properties in the highest degree; and as movement and knowledge seemed to connote what is lightest and most rarified, they concluded that the soul was fire, which is the lightest and most rarified of bodies. And. while many were of this opinion and thought the soul was fire, Democritus more subtly and rationally explained ‘the reason for either fact’, that is, he expressed more clearly the nature of movement and of knowledge. He held, as we have seen,, that all things are made of atoms; and though for him these atoms were primary he maintained, nevertheless, that the round ones were of the nature of fire, so that the soul, he said, was composed of spherical atoms. Considered as first principles, these atoms were by nature cognitive, but considered as spherical they were mobile; hence he said that the soul knows and moves all things precisely because it is made up of these round, indivisible bodies. And in assuming that they were of the nature of fire, he agreed with those who thought that everything was fiery.

§ 57. Then at ‘Anaxagoras, however’, Aristotle gives the view of Anaxagoras who agreed with the others already mentioned in ascribing knowledge and motion to the soul. Anaxagoras, as we saw, sometimes appears to distinguish between soul and intellect, but sometimes he uses both terms as though they meant the same thing. He ascribes to the soul motive power and knowledge, but he also says that intellect knows and moves all things, thus identifying the soul and the intellect. But he differed from the others in this, that whereas Democritus held that the soul was corporeal by nature, being composed of material elements, Anaxagoras said that intellect was ‘simple’, excluding intrinsic division from its essence, and ‘unmixed’, excluding composition with anything else, and ‘pure’, excluding any addition to it from outside. But he ascribed movement and knowledge to one and the same principle, i.e. the intellect; for intellect of its nature knows; and movement pertains to it, so he said, because it moves everything else.

§ 58. Next, at ‘It seems that Thales’, he states the opinion of a philosopher called Thales who had only this in common with the others mentioned above, that he identified soul with a motive force. This Thales was one of the Seven Wise Men; but while the others studied moral questions, Thales devoted himself to the world of nature and was the first natural philosopher. Hence Aristotle remarks ‘from what they recollect etc.’, referring to those who said that water was the basic principle of things. For Thales thought that the way to find the principle of all things was by searching into the principle of living things, and since all the principles or seeds of living things are moist, he thought that the absolutely first principle must be the most moist of things; and this being water, he said water was that principle. Yet he did not follow his theory to the point of saying that soul was water; rather, he defined it as that which has motive force. Hence he asserted that a certain stone, the magnet, had a soul because it moved iron. Anaxagoras and Thales, then, are included in the present list; not for identifying the soul with fire, but because the former said that the soul was the source of knowledge and sensation, and the latter that it was at the ,origin of movement.

§ 59. Where he says, ‘Now Diogenes’, Aristotle alludes to those who thought that air was the first principle and the soul. There were three of these. First there was Diogenes who held that air was the first principle and also the finest-grained of all bodies, and that the soul therefore was air,—hence its power to know and move. The knowing power was due to the fact that air was (as he said) the first principle; for as knowledge is through likeness, as we have seen, the soul could not know all things unless it included the principles of all. And the moving power was due, he said, to the fact that air was the finest-grained of bodies and therefore the most mobile.

§ 60. Then at ‘Heraclitus, however’ he states the second opinion, that of Heraclitus who thought that not mere air but vapour, the blend of air and water, was the first principle. He could not allow that this was either water by itself, or fire, or air; it had to be something betwixt and between, because, being a materialist, he was concerned to find a principle midway between the opposite extremes of material quality. Thinking that vapour answered this requirement most precisely, he said that the soul was vapour; which explained its extraordinary capacity to know and to move. His view was, indeed, that everything was in continual flux, that nothing stayed the same even for one hour, and that no definite statement could be made about anything. And it was just because vapour is so unstable that he identified it with the first principle of all things; which, he said, was a soul. As the first principle, soul has the power to know, whilst as the least material and most fluid of things it has movement.

61. Thirdly, at ‘Alcmaeon seems,’ he gives the third opinion, Alcmaeon’s, which agrees with the others only as regards movement. This man said that the soul was pre-eminently a thing in motion, resembling in this the immortal heavenly bodies with their heavenly and divine nature. For he thought that the perpetual movement of the sun and moon and the rest, was the cause of their being immortal; and that the same inference was valid in the case of the soul.

§ 62. Then at ‘Some cruder thinkers’, Aristotle states an opinion of some who made water the first principle. For there were certain rather crude followers of Thales who tried to make the principle of one particular thing an analogy of the first principle of Nature as a whole. Observing that moisture was fundamental to living things they concluded that it must be the first principle of an things; in short, that the latter was water. So far indeed they followed their master, Thales; but whereas he, though admitting water to be the first principle, would not, as we have seen, allow that the soul was water, but rather a motive force, his cruder disciples (such as Hippo) asserted that it was water. Hippo tried to refute those who said the soul was blood with the argument that blood is not the generating seed (which they called ‘the inchoate soul’) of animate things. He identified this with water on account of its humidity.

§ 63. Next, at ‘Others, such as Critias’ he alludes to a philosopher who was more interested in the soul’s knowledge. He was still cruder in his expressions, saying that the soul itself was blood. His reason was that sense-perception only takes place in animals through the medium of blood: for the bloodless organs, such as bones, nails and teeth are without sensation (he forgot the nerves which are extremely sensitive and yet bloodless). If then, he said, the soul is the root of knowledge, the soul must be blood. it was Critias who said this.

§ 64. In case anyone should wonder why he has not mentioned earth along with the other elements, Aristotle, at, ‘Opinions have etc.,’ explains that his predecessors’ views on the soul followed on what they thought about the first principles; and as nobody judged earth to be a first principle, nobody said it was the soul; unless we count those—such as Democritus and Empedocles—who said that soul was, or was composed of, all the principles.

§ 65. Then, at ‘All, taken together,’ he summarises, concluding this part of the enquiry; and first with reference to the elements or principles themselves, and then with regard to the contrarieties that are found in them.

First, then, he notes that the soul has been described by all-in terms of these three notes: fineness of grain or texture (incorporeality); knowledge; movement; and that each of these notes has been also traced back to a first principle. For that is called a principle which is simple. Also a principle, it is said, is essentially cognitive (for, to recall what, was said above, I since like is known by like, they said that the soul was composed of, or even was, the elements of all things. Anaxagoras, to be sure, is an exception with his pure unmixed Intellect). Again, they identified the chief motive-force in things with a ‘principle’ since a principle is what is least corporeal. And the soul’s knowledge of all things proves, they said, that it was composed of all the principles or elements. All their theories turn on this correspondence between the soul and the first principles. Whoever posited some one cause or principle or element, such as fire, air or water, identified just that one with the soul. So, too, whoever upheld many principles either identified them with the soul. or with its component elements.

§ 66. Having excepted Anaxagoras, touching the theory of the soul’s composition, he goes on, at ‘But Anaxagoras’ to show how this man differed from the others. He alone, says Aristotle, denied the passivity of the intellect, its share in the nature of the things that it knows. But how intellect knows, Anaxagoras does not say; nor can one infer anything certain from what he does say.

§ 67. To end this section, Aristotle summarises what he has to say touching the contrariety of the above-mentioned principles to one another. Some, he says, arrange the first principles of things in pairs of opposites; and the soul also they regard as a synthesis of contraries. Thus Empedocles thought that the heat and cold, the moisture and dryness which he found ‘in the elements were intrinsic to the soul also. As earthy, he said, we know earth, as watery water, and so on. Others found their first principle in only one element, whose particular quality they then attributed to the soul. If it was fire, then the soul, they said, was hot; if water, then the soul was cold. According to the principle assumed so was the quality attributed to the soul, as though it shared in the nature of heat or cold etc. This is clear from the names they gave to the soul. Those who said it was hot gave it names derived from zaein or zooein, meaning to live, which itself comes from zeein, meaning to boil; while others who said it was cold called it psychron, meaning cold, whence comes psyche, a term applied to the soul because the coolness caused by breathing preserves animal life. Those who thought the soul by nature hot, named it from life; those who thought it by nature cold, from respiration. And Aristotle concludes by saying that the foregoing are the opinions handed down about the soul, together with the grounds on which they are maintained.

TEXT

405b32–406b14

BOOK I, CHAPTER III

PREVIOUS THEORIES

SOUL AS A SELF-MOVING ESSENCE

The first thing to be considered is movement. For perhaps it is not only false to say that this is the essence of the soul, as some mean when they say the soul is self-moving, or is able to move itself, but that there should be movement in it at all is an impossibility. It has already been stated that it is not necessary that everything that causes motion be itself moving. For everything moves in one of two ways: either by another, or of itself. We say, ‘by another’, of anything that moves through being in that which moves, like sailors; for these are not in motion in the same way as the ship. The latter moves of itself, but they through being in what moves. This is evident if we consider their parts. Walking is the proper motion of the feet—and also of men—; but for the time being the sailors do not walk. Movement being thus predicated in two ways, we now turn to the soul, asking whether it moves of itself and participates in motion. §§ 68-74

Since there are four kinds of movement (local, by alteration, by increase, by decrease) its motion must be one of these, or some, or all. But if its movement is not incidental, then motion will be in it by nature: and if so, it will be [in] place; for all the aforesaid movements are in place. If it is the essence of the soul to move itself, to be in motion will not be in it incidentally, as in what is white or three cubits long; for these also participate in movement, but incidentally. For what moves is the body in which these inhere; hence of themselves they have no place; but the soul has it, if indeed it naturally participates in motion. §§ 75-7

Further, if it moves by nature, so it will move by force; and if by force, then, by nature. And its rest will be in the same way. Whithersoever it moves by nature, there it will come to rest by nature; and likewise wheresoever it is moved by force, there it will come to rest by force. But what kind of enforced motions and rests will there be in the soul? To find an answer is not easy, nor, even to imagine one! §§ 78-9

Again, if it moves upwards, it will be fire; and if downwards, earth; for such are the movements of these bodies; and the same holds of the intermediate [elements]. § 80

Since it seems to move the body, it would seem reasonable [to say] that it does so by the same motions as those by which it moves itself. If so, then it is true to say, conversely, that just as the body moves, the soul also moves. Now the body moves by change of place; hence the soul too will move in accordance with the body, either the whole or the parts being transposed. If this is so, then it might happen that after leaving the body it could return to it. (But it is utterly impossible that the dead rise again.) And it would follow that dead animals could rise again. §§ 81-83

If it does move, however, by something else, its motion will be incidental; for certainly an animal can be driven by force. But what has self-movement as of its essence cannot be moved by another, save incidentally; as that which is good in itself or for its own sake cannot exist for the sake of another, or on account of another.

One might certainly say that, if the soul is moved at all, it is moved by the objects of sensation. §§ 84-5

But if it moves itself it also is in motion. Hence if all motion is a displacement of the moved as such, then the soul must be displaced from its own essence by itself, unless its movement be incidental; but [in fact] this is a self-movement of its essence. § 86

ST. THOMAS’S COMMENTARY

LECTIO SIX

§ 68. The Philosopher now begins to criticise the theories he has been recounting. These theories amount to three statements about the soul: that it is the source of movement and of knowledge, and that it is in a special way incorporeal. The two former attributions, the principal ones, have been predicated of the soul in an absolute sense, as referring directly to its essence. The third is, however, true in one sense and false in another. For if immateriality is taken as predicated simply and absolutely of the soul, then the statement is true; for soul is certainly the least material and most rarified of things. But if it is predicated only in relation to the body, as if to say that soul is the least material of bodies, then the statement is not true. Hence the Philosopher sets to work only with the two former attributions, of movement and of knowledge.

§ 69. This part of the treatise falls into three divisions. Aristotle first argues against the philosophers who had made the soul the source of movement; then at ‘There are then three ways’ against those who regarded it as the seat of knowledge; and thirdly, at ‘Since knowledge pertains’ he raises the question whether movement, feeling and knowing ought to be attributed to the soul as to one principle or several. The first of these divisions is again divided. He first adduces objections against simply identifying the soul itself with a source of movement; and then against an opinion, proceeding from this identification, according to which the soul was also a self-moving number. (This comes at ‘Much the most unreasonable’. ) The former argument again subdivides into, first a criticism of the way in which these philosophers had predicated movement of the soul, and secondly, at ‘One might with more reason,’ a query whether this predication might have been made differently. Then the criticism is divided into, first, a general argument against all who said that the soul was the source of movement; and secondly, at ‘Some say that a soul moves’ a series of particular discussions of special points. Finally, the general argument is subdivided. First, he says what he intends to do; secondly, he argues ‘in support of his own opinion. The latter begins at ‘Since there are four kinds of movement’.

§ 70. He begins then by remarking that philosophers have studied the soul from two points of view, from motion and from knowledge. This is clear from what has been said. And Aristotle says that he will start from motion. Now all the others who started from this point of view had one notion in common, that everything that produces movement is itself moving. They thought therefore that if soul is by nature a cause of movement, it must be by its nature a moving essence. So they put movement into its definition, calling it something that moves itself.

§ 71. Now here there are two disputable points; the theory itself is disputable, and so is the principle upon which it rests. The principle presupposed as a self-evident truth, namely that every active mover is itself in movement, is in fact not true, as is clearly enough shown in Book VIII of the Physics, where Aristotle proves the existence of an unmoved mover. And as to this, we may give here a short proof that if a thing produces movement it does not have to be in movement itself. It is clear that in so far as a thing produces movement it is in act, and in so far as it is caused to move, it is in potency. (if then as causing movement it were moved), the same thing would be in act and potency in the same respect; which hardly makes sense.

§ 72. But even setting this difficulty aside, the theory that the soul is in movement is disputable. Its upholders indeed added the further proposition, that movement was of the soul’s essence; but Aristotle denies both parts of this theory where he says, ‘For perhaps’, etc. He puts it like this because he has not yet proved his assertion, namely that not only is it false to say that movement is of the essence of the soul (which is what they imply when they define the soul as an actual or potential self-mover) but that it is also quite impossible that the soul should move at all.

§ 73. That not everything which causes movement need itself be moved was shown in an earlier work, Book VIII of the Physics. Now in any self-mover there are two things to be considered, the thing moving, and the thing moved; and the former cannot as such be the same as the latter. In living things, however, though the moving part is not moved in itself, absolutely speaking, yet it is moved indirectly. For there are two kinds of movement, direct and indirect: direct, when a thing itself is moving, e.g. a ship; indirect when a thing itself is at rest, but moved with the movement of something else which contains it, as the sailor on board ship moves with the ship’s movement, not his own. So the ship moves directly and in itself, but the sailor only in an accidental way or relatively. This is clear if we consider that when anything moves in itself, its parts are moving, as in walking the feet make the first movement; but once the sailor is on board this does not happen. Movement then can be taken in either of these two senses; but since the philosophers we are discussing said that the soul is moved in itself, directly, we can forgo at present the question whether it is moved indirectly, and consider only whether it is directly affected by movement, as they maintained.

§ 74. To show that the soul does not move in itself, Aristotle uses six arguments, with regard to which we should note that, while they may not appear very cogent, still they are effective in relation to the theory he is criticising. For it is one thing to argue out the simple truth of a question, and another to reason against a particular theory; in the former case you have to make sure that your premisses are true, but in the latter you proceed from what your adversary concedes or asserts. Hence it is that when Aristotle criticises the views of others, he often seems to use rather weak arguments. In each case he is, in fact, destroying his adversary’s position by drawing out its logical consequences.

§ 75. The first argument begins at ‘Since there are four kinds’, and may be stated as follows. If the soul moves, its movement is either direct (in the sense explained) or indirect. if indirect, then it is not of the essence of the soul (which is against their opinion), and the soul moves in the same way as whiteness or 3 inches, which are accidental qualities moving only with the thing that is white or 3 inches long, and not themselves, as such, requiring a position in space. But if the soul moves in itself, it moves in one of the four kinds of movement: change of place, growth, decrease or alteration. Coming-to-be and passing-away are not movements, strictly speaking, but changes, because they are instantaneous, whilst movements are successive. Hence the soul will have to move in one of these four ways—from place to place; by increase or decrease in size; or by qualitative alteration. But if all these movements involve position in space, the soul will then be localised in space.

§ 76. There seem to be two doubtful points in this argument. The first is that, while it is clear enough as regards locomotion, growth and decrease, it suggests a difficulty about alteration. Some meet this difficulty by saying that as only bodies are subject to alteration, and all bodies are in place, alteration itself may be said to occur in place. But this does not keep to the letter of the argument: Aristotle says that this kind of movement is in place and not merely according to place. Movement in place is quite different from movement according to place; and, following Aristotle, I maintain that alteration certainly occurs in place. Of itself, and not simply because of its localised subject, it is in place; for, when any alteration occurs, the agent producing it must draw near to the thing altered; otherwise nothing would ever be altered. And since drawing near is a local movement, it follows that here and now the cause of a given alteration is a change in place.

§ 77. The second difficulty is that these philosophers do not in fact see anything unreasonable in the soul’s being in place, since they maintain that it moves in itself, absolutely. So Aristotle’s objection seems to misfire. To this two answers might be given, (a) that the objection to the soul’s being in place will become clearer as we proceed, and (b) that if the soul were in place, it would have to be assigned a definite position in the body and thus would not be the form of the whole body. This reinforces the objection to the soul’s being in place.

§ 78. The second argument, at ‘Further, if it moves’, is this. If the soul moves ‘absolutely’ from place to place, the movement must be natural to it. But anything that can be moved naturally can be moved violently.’ Now its natural movement implies a natural ceasing to move; and therefore also its enforced, violent movement implies an enforced ceasing to move. Hence the soul may both move and stop moving under compulsion; which is impossible if by nature both its movement and ceasing to move are spontaneous.

§ 79. A difficulty here seems to be that what moves naturally does not in fact move under compulsion. I answer that what Aristotle says is false absolutely speaking, but true relative to the theory under discussion. For these philosophers maintained that the only bodies that moved with a natural movement were the four elements; in which we do observe both natural and enforced movement and ceasing to move. This opinion is presupposed by the argument.

§ 80. The third argument, at ‘Again, if,’ runs as follows: these men who ascribe movement primarily to the soul, and to the body only as derived from the soul, also say that this movement is due to one or other of the elements, fire or earth or one of the others. But if the soul moved with the nature of fire it would only rise; if with the nature of earth it would only sink; whereas in fact it moves in all directions. This argument also is ad hominem.

§ 81. The fourth argument comes at ‘Since it seems’. It is this. You say that it is in moving the body that the soul moves. Logically, then, it follows that it moves the body by its own movements; and conversely that it is moved by the same movements which move the body. But the body moves by changing position in space; so also then the soul. But if the soul’s local movements affect the body, the soul might, after leaving the body, enter it once more. And since it is the soul’s presence that gives life to the body, it follows that dead animals might, even naturally, come back to life: which is impossible.

§ 82. Against this argument some have objected that it ignores the difference between the movements which affect the soul itself and those by which it moves other things, including the body. The former are movements of desire and will; not so the latter. But in reply one may say that desires and volitions and so on are not properly ‘movements’ of the. soul but ‘operations’. ‘Movements’ and ‘operations’ are different: a movement is an act of something that is incomplete, whereas an operation is an act of a subject already possessing full actuality. Still, what Aristotle says is true relative to the theory under discussion; for this had identified all the movements of the soul with those by which it moved the body.

§ 83. But is it true that if the soul had local movement dead animals would come to life again? Well, some philosophers have maintained that the soul pervades the whole body, forming a unity with it through some kind of proportion, and that the two cannot be separated without this proportion being destroyed; so that, so far as this view is concerned, the conclusion would not follow. But it does follow from—and is a valid objection against—the opinion of those who say the soul is located in the body as in a vessel which it sometimes enters and sometimes leaves.

§ 84. The fifth argument comes at ‘If it does move’, and runs as follows. It is clear that when anything is of the essence of a given subject its presence in the latter does not need, except incidentally, to be explained by anything else. If then the soul is essentially moving, it is mobile of its own nature; it does not need to be moved through or by anything else. But we know that it is in fact moved by sensible objects when it senses, and by things desirable when it desires; therefore it does not move of itself.

§ 85. The Platonists meet this argument by denying that the soul is moved by sensible objects; these, they say, are merely involved in the soul’s own movement when it passes from one object to another. But this is untrue. As Aristotle has proved, the intellectual potency is brought into act precisely by means of the sensible objects as apprehended; so that it is moved by them in this way.

§ 86. The sixth argument begins at ‘But if it moves itself’. Clearly, if the soul is self-moving, its own essence governs its movement. But in every movement the moving thing comes away or proceeds from that which moves it and governs its movement; for instance, if anything is moved by a quantity, it departs and proceeds from the latter. If then the soul is moved by its own essence (as they say) it must depart or proceed from its own essence; which is as much as to say that it causes its own destruction. How then could it be through movement that the soul becomes god-like and immortal, as some philosophers whom we have mentioned supposed?, This argument bears against those who did not distinguish between movement proper and operation. For movement implies that what is moved comes away from the cause of movement; but operation is a perfection intrinsic to the operating agent itself

TEXT

406b15–407a2

BOOK I, CHAPTER III, CONTINUED

SOUL AS A MOVER OF THE BODY

DEMOCRITUS AND PLATO

Some say that a soul moves the body in which it dwells just as it moves itself; as did Democritus, who spoke like Philip the comic poet; for the latter relates that Daedalus made a wooden Venus mobile by pouring quicksilver into it. Democritus, then, spoke in like manner, saying that there are in movement indivisible globules of which the nature is to be never at rest, and which therefore draw together and move the whole body. §§ 87-8

Now, what we would ask is, whether this is also the cause of coming to rest? How it could be, on this hypothesis, is difficult to see, indeed impossible. § 89

The soul seems, in general, not to move the animate being in this way, but rather by a sort of choice and understanding. § 90

In the same way, the Timaeus sets out a physical theory as to how the soul moves the body. For, from the fact that the soul moves itself, it moves the body, as a result of its connection with the body. § 91

‘Being compounded of the elements and divided according to harmonic numbers, so that it have a connatural sense of harmony, and the whole be borne along with well attuned motions, §§ 92-8

[God] bent the straight line into a circle, and, dividing it, made out of one two circles, adjusted at two points; and, again, he divided one of these into seven circles, as though the heavenly motions were the soul’s motions.” §§ 99-106

ST. THOMAS’S COMMENTARY

LECTIO SEVEN

§ 87. Having argued in a general way against the view that movement pertains essentially to the soul, the Philosopher now brings forward arguments against particular philosophers whose theories of the movement of the soul seem to give rise to some special difficulty. These arguments fall into three groups. First, he opposes an opinion of Democritus; then, at ‘In the same way’, one of Plato; and thirdly, at ‘There is another opinion’ another theory.

He begins, then, by stating the view of Democritus on the soul’s movement; and then brings objections against it.

§ 88. This theory has already been referred to by Aristotle in his fourth objection to the view that the soul moves in itself and by this movement makes the body move. If the soul moves the body, he has said, it must do so in virtue of its own movement. This was admitted by those who said that each soul moved its own body in a manner corresponding to the movement in itself; among whom was Democritus who made use of the following illustration. There was a certain comic dramatist called Philip who tells somewhere of one Daedalus, that he made a wooden statue of the goddess Venus, and that this statue, being filled with quicksilver, was able to move. It moved as the quicksilver moved. And what Democritus said of the soul’s movement was rather similar. The soul, he said, (as has been noted above) was composed of indivisible spheres or atoms which, being round in shape, were always moving about, and by their incessant movement made the whole body cohere and move accordingly.

§ 89. Then, at ‘Now, what we, etc.’, Aristotle puts two objections to this. First, it is agreed that in animals the soul is the cause of resting, as well as the cause of movement. But according to Democritus the soul is never the cause of rest, though it is the cause of animal movements. For he could hardly maintain that those spherical atoms ever rested if they never cease to move.

§ 90. Again, at ‘The soul seems’ he puts a second objection. The movement caused by quicksilver in the statue is obviously not spontaneous; it is a compelled movement. On the contrary, that of the soul is spontaneous, proceeding from mind and will. Hence the view of Democritus seems worthless.

§ 91. Then at ‘In the same way’ he first states the opinion of Plato, which, at ‘Now in the first place,’ he will reject. But before explaining what Plato said about the soul he shows its similarity to the theory of Democritus. As Democritus had supposed that the soul’s movements moved the body to which it was joined, so also did Timaeus, a speaker introduced by Plato. For he said that soul moves body in so far as soul itself moves; because the two are, as it were, bound up together.

§ 92. With ‘Being compounded, etc.’ Aristotle makes Plato’s view explicit; first as to what constitutes the essence of the soul, at ‘God bent, etc.,’ as to how movement proceeds from it. Regarding the former question, note that the words quoted here are used by Plato in the Timaeus and refer to the Soul of the world which, according to him, is imitated by inferior souls. So when he touches, as here, on the nature of the World-Soul, he refers also, in a way, to any soul. Now Plato, for the reason already given, maintained that the essence of all things was numerical; and that in number the formal element, so to say, was one and the material element two—all numbers being made up of one and two. And as odd numbers retain something of the indivision of one, he laid down two elements of number, the even and the odd, attributing to the odd identity and finitude, but to the even difference and infinity.

§ 93. Some explanation of this theory may be found in the Physics, Book III. If odd numbers are added to unity in sequence the same type of number 2 always results; e.g. if 3, the first odd number, is added to 1, you get the square number 4; if to 4 You add the second odd number, 5, you get 9, Which is also a square number; and so on to infinity. But with even numbers the result is always a different type of number. Add 2, t