The problem might be suggested: if thinking is a passive affection, then if thought is simple and impassible and has nothing in common with anything else, as Anaxagoras says, how can it come to think at all? For interaction between two factors is held to require a precedent community of nature between the factors. [25] Again it might be asked, is thought a possible object of thought to itself? For if thought is thinkable per se and what is thinkable is in kind one and the same, then either thought will belong to everything, or it will contain some element common to it with all other realities which makes them all thinkable.
Have not we already disposed of the difficulty about interaction involving a [30] common element, when we said that thought is in a sense potentially whatever is thinkable, though actually it is nothing until it has thought? What it thinks must be34 in it just as characters may be said to be on a writing-table on which as yet [430a1] nothing actually stands written: this is exactly what happens with thought.
Thought is itself thinkable in exactly the same way as its objects are. For in the case of objects which involve no matter, what thinks and what is thought are identical; for speculative knowledge and its object are identical. (Why thought is [5] not always thinking we must consider later.) In the case of those which contain matter each of the objects of thought is only potentially present. It follows that while they will not have thought in them (for thought is a potentiality of them only in so far as they are capable of being disengaged from matter) thought may yet be thinkable.
[10] 5 · Since in every class of things, as in nature as a whole, we find two factors involved, a matter which is potentially all the particulars included in the class, a cause which is productive in the sense that it makes them all (the latter standing to the former, as e.g. an art to its material), these distinct elements must likewise be found within the soul.
And in fact thought, as we have described it, is what it is by virtue of becoming [15] all things, while there is another which is what it is by virtue of making all things: this is a sort of positive state like light; for in a sense light makes potential colours into actual colours.
Thought in this sense of it is separable, impassible, unmixed, since it is in its essential nature activity (for always the active is superior to the passive factor, the originating force to the matter).
[20] Actual knowledge is identical with its object: in the individual, potential knowledge is in time prior to actual knowledge, but absolutely it is not prior even in time. It does not sometimes think and sometimes not think. When separated it is alone just what it is, and this alone is immortal and eternal (we do not remember [25] because, while this is impassible, passive thought is perishable); and without this nothing thinks.
6 · The thinking of indivisibles is found in those cases where falsehood is impossible: where the alternative of true or false applies, there we always find a sort of combining of objects of thought in a quasi-unity. As Empedocles said that ‘where [30] heads of many a creature sprouted without necks’35 they afterwards by Love’s power were combined, so here too objects of thought which were separate are combined, e.g. ‘incommensurate’ and ‘diagonal’: if the combination be of objects [430b1] past or future the combination of thought includes in its content the date. For falsehood always involves a combining; for even if you assert that what is white is not white you have combined not-white.36 It is possible also to call all these cases division. However that may be, there is not only the true or false assertion that [5] Cleon is white but also the true or false assertion that he was or will be white. In each and every case that which unifies is thought.
Since the word ‘indivisible’ has two senses, i.e. may mean either ‘not capable of being divided’ or ‘not actually divided’, there is nothing to prevent thought from thinking of what is undivided, e.g. when it thinks of a length (which is actually undivided) and that in an undivided time; for the time is divided or undivided in the [10] same manner as the line. It is not possible, then, to tell what part of the line it was thinking of in each half of the time: the object has no actual parts until it has been divided; if in thought you think of each half separately, then by the same act you divided the time also, the half-lines becoming as it were new wholes of length. But if you think of it as a whole consisting of these two parts, then also you think of it in a time which corresponds to both parts together. (But what is not quantitatively but [15] qualitatively simple is thought of in a simple time and by a simple act of the soul.)37
But that which thought thinks of and the time in which it thinks are in this case divisible only incidentally and not as such. For in them too there is something indivisible (though, it may be, not separable) which gives unity to the time and the whole of length; and this is found equally in every continuum whether temporal or [20] spatial.
Points and similar instances of things that divide, themselves being indivisible, are realized in consciousness in the same manner as privations.
A similar account may be given of all other cases, e.g. how evil or black is cognized; they are cognized, in a sense, by means of their contraries. That which cognizes must be its objects potentially, and they must be in it. But if there is anything that has no contrary,38 then it knows itself and is actually and possesses [25] independent existence.
Assertion is the saying of something concerning something, as too is denial, and is in every case either true or false: this is not always the case with thought: the thinking of the definition in the sense of what is is for something to be is never in error nor is it the assertion of something concerning something; but, just as while the seeing of the special object of sight can never be in error, seeing whether the white object is a man or not may be mistaken, so too in the case of objects which are without matter.
7 · Actual knowledge is identical with its object: potential knowledge in the [431a1] individual is in time prior to actual knowledge but absolutely it has no priority even in time; for all things that come into being arise from what actually is. In the case of sense clearly the sensitive faculty already was potentially what the object makes it to be actually; the faculty is not affected or altered. This must therefore be a [5] different kind of movement; for movement is an activity of what is imperfect, activity in the unqualified sense, i.e. that of what has been perfected, is different.
To perceive then is like bare asserting or thinking; but when the object is pleasant or painful, the soul makes a sort of affirmation or negation, and pursues or avoids the object. To feel pleasure or pain is to act with the sensitive mean towards [10] what is good or bad as such. Both avoidance and appetite when actual are identical with this: the faculty of appetite and avoidance are not different, either from one another or from the faculty of sense-perception; but their being is different.
To the thinking soul images serve as if they were contents of perception (and [15] when it asserts or denies them to be good or bad it avoids or pursues them). That is why the soul never thinks without an image. The process is like that in which the air modifies the pupil in this or that way and the pupil transmits the modification to some third thing (and similarly in hearing), while the ultimate point of arrival is one, a single mean, with different manners of being.
With what part of itself the soul discriminates sweet from hot I have explained [20] before and must now describe again as follows: That with which it does so is a sort of unity, but in the way a boundary is; and these things being one by analogy and numerically, are each to each as the qualities discerned are to one another (for what difference does it make whether we raise the problem of discrimination between [25] disparates or between contraries, e.g. white and black?). Let then C be to D as A, white is to B, black: it follows alternando that C : A :: D : B. If then C and A belong to one subject, the case will be the same with them as with D and B; D and B form a single identity with different modes of being; so too will the former pair. The same [431b1] reasoning holds if A be sweet and B white.
The faculty of thinking then thinks the forms
in the images, and as in the former case what is to be pursued or avoided is marked out for it, so where there is no sensation and it is engaged upon the images it is moved to pursuit or avoidance. [5] E.g. perceiving by sense that the beacon is fire, it recognizes in virtue of the general faculty of sense that it signifies an enemy, because it sees it moving; but sometimes by means of the images or thoughts which are within the soul, just as if it were seeing, it calculates and deliberates what is to come by reference to what is present; and when it makes a pronouncement, as in the case of sensation it pronounces the object to be pleasant or painful, in this case it avoids or pursues; and so generally in cases of action.39
[10] That too which involves no action, i.e. that which is true or false, is in the same province with what is good or bad: yet they differ in this, that the one is absolute and the other relative to someone.
The so-called abstract objects the mind thinks just as, in the case of the snub, one might think of it qua snub not separately, but if anyone actually thought of it qua hollow40 he would think of it without the flesh in which it is embodied: it is thus [15] that the mind when it is thinking the objects of mathematics thinks of them as separate though they are not separate. In every case the mind which is actively thinking is the objects which it thinks. Whether it is possible for it while not existing separate from spatial conditions to think anything that is separate, or not, we must consider later.
[20] 8 · Let us now summarize our results about soul, and repeat that the soul is in a way all existing things; for existing things are either sensible or thinkable, and knowledge is in a way what is knowable, and sensation is in a way what is sensible: in what way we must inquire.
Knowledge and sensation are divided to correspond with the realities, potential [25] knowledge and sensation answering to potentialities, actual knowledge and sensation to actualities. Within the soul the faculties of knowledge and sensation are potentially these objects, the one what is knowable, the other what is sensible. They must be either the things themselves or their forms. The former alternative is of course impossible: it is not the stone which is present in the soul but its form.
[432a1] It follows that the soul is analogous to the hand; for as the hand is a tool of tools, so thought is the form of forms and sense the form of sensible things.
Since it seems that there is nothing outside and separate in existence from [5] sensible spatial magnitudes, the objects of thought are in the sensible forms, viz. both the abstract objects and all the states and affections of sensible things. Hence no one can learn or understand anything in the absence of sense, and when the mind is actively aware of anything it is necessarily aware of it along with an image; for images are like sensuous contents except in that they contain no matter.
Imagination is different from assertion and denial; for what is true or false [10] involves a synthesis of thoughts. In what will the primary thoughts differ from images? Must we not say that neither these nor even our other thoughts are images, though they necessarily involve them?
9 · The soul of animals is characterized by two faculties, the faculty of [15] discrimination which is the work of thought and sense, and the faculty of originating local movement. Sense and thought we have now sufficiently examined. Let us next consider what it is in the soul which originates movement. Is it a single part of the soul separate either spatially or in definition? Or is it the soul as a whole? [20] If it is a part, is that part different from those usually distinguished or already mentioned by us, or is it one of them? The problem at once presents itself, in what sense we are to speak of parts of the soul, or how many we should distinguish. For in a sense there is an infinity of parts: it is not enough to distinguish, with some thinkers, the calculative, the passionate, and the desiderative, or with others the [25] rational and the irrational; for if we take the dividing lines followed by these thinkers we shall find parts far more distinctly separated from one another than these, namely those we have just mentioned: the nutritive, which belongs both to plants and to all animals, and the sensitive, which cannot easily be classed as either irrational or rational; further the imaginative, which is, in its being, different from [432b1] all, while it is very hard to say with which of the others it is the same or not the same, supposing we determine to posit separate parts in the soul; and lastly the appetitive, which would seem to be distinct both in definition and in power from all hitherto enumerated.
It is absurd to break up the last-mentioned faculty: for wish is found in the [5] calculative part and desire and passion in the irrational; and if the soul is tripartite appetite will be found in all three parts. Turning our attention to the present object of discussion, let us ask what that is which originates local movement of the animal.
The movement of growth and decay, being found in all living things, must be attributed to the faculty of reproduction and nutrition, which is common to all: [10] breathing in and out, sleep and waking, we must consider later: these too present much difficulty: at present we must consider local movement, asking what it is that originates forward movement in the animal.
That it is not nutritive faculty is obvious; for this kind of movement is always [15] for an end and is accompanied either by imagination or41 by appetite; for no animal moves except by compulsion unless it has an impulse towards or away from an object. Further, if it were the nutritive faculty, even plants would have been capable of originating such movement and would have possessed the organs necessary to carry it out. Similarly it cannot be the sensitive faculty either; for there are many [20] animals which have sensibility but remain fast and immovable throughout their lives.
If then Nature never makes anything without a purpose and never leaves out what is necessary (except in the case of mutilated or imperfect growths; and that here we have neither mutilation nor imperfection may be argued from the facts that such animals can reproduce their species and rise to completeness of nature and decay to an end), it follows that, had they been capable of originating forward [25] movement, they would have possessed the organs necessary for that purpose. Further, neither can the calculative faculty or what is called thought be the cause of such movement; for mind as speculative never thinks what is practicable, it never says anything about an object to be avoided or pursued, while this movement is always in something which is avoiding or pursuing an object. No, not even when it is aware of such an object does it thereby enjoin pursuit or avoidance of it; e.g. the [30] mind often thinks of something terrifying or pleasant without enjoining the emotion of fear. It is the heart that is moved (or in the case of a pleasant object some other [433a1] part). Further, even when thought does command and bids us pursue or avoid something, sometimes no movement is produced; we act in accordance with desire, as in the case of moral weakness. And, generally, we observe that the possessor of [5] medical knowledge is not necessarily healing, which shows that something else is required to produce action in accordance with knowledge; the knowledge alone is not the cause. Lastly, appetite too is incompetent to account fully for movement; for those who successfully resist temptation have appetite and desire and yet follow thought and refuse to enact that for which they have appetite.
10 · These two at all events appear to be sources of movement: appetite and [10] thought (if one may venture to regard imagination as a kind of thinking; for many men follow their imaginations contrary to knowledge, and in all animals other than man there is no thinking or calculation but only imagination).
Both of these then are capable of originating local movement, thought and appetite: thought, that is, which calculates means to an end, i.e. practical thought [15] (it differs from speculative thought in the character of its end); while appetite is in every form of it relative to an end; for that which is the object of appetite is the stimulant of practical thought; and that which is last in the process of thinking is the beginning of the action. It follows that there is a justification for regarding these two as the sources of movement, i.e. appetite and practical thought; for the object
of appetite starts a movement and as a result of that thought gives rise to movement, [20] the object of appetite being to it a source of stimulation. So too when imagination originates movement, it necessarily involves appetite.
That which moves therefore is a single faculty and the faculty of appetite; for if there had been two sources of movement—thought and appetite—they would have produced movement in virtue of some common character. As it is, thought is never found producing movement without appetite (for wish is a form of appetite; and when movement is produced according to calculation it is also according to wish), [25] but appetite can originate movement contrary to calculation, for desire is a form of appetite. Now thought is always right, but appetite and imagination may be either right or wrong. That is why, though in any case it is the object of appetite which originates movement, this object may be either the real or the apparent good. To produce movement the object must be more than this: it must be good that can be brought into being by action; and only what can be otherwise than as it is can thus [30] be brought into being. That then such a power in the soul as has been described, i.e. that called appetite, originates movement is clear. Those who distinguish parts in [433b1] the soul, if they distinguish and divide in accordance with differences of power, find themselves with a very large number of parts, a nutritive, a sensitive, an intellective, a deliberative, and now an appetitive part; for these are more different from one another than the faculties of desire and passion.
Since appetites run counter to one another, which happens when a principle of [5] reason and a desire are contrary and is possible only in beings with a sense of time (for while thought bids us hold back because of what is future, desire is influenced by what is just at hand: a pleasant object which is just at hand presents itself as both pleasant and good, without condition in either case, because of want of foresight into what is farther away in time), it follows that while that which originates [10] movement must be specifically one, viz. the faculty of appetite as such (or rather farthest back of all the object of that faculty; for it is it that itself remaining unmoved originates the movement by being apprehended in thought or imagination), the things that originate movement are numerically many.
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