by Aristotle
If it is true that the movement, i.e. the acting, and the being acted upon,21 is to be found in that which is acted upon, both the sound and the hearing so far as it is actual must be found in that which has the faculty of hearing; for it is in the passive factor that the actuality of the active or motive factor is realized; that is why that [5] which causes movement may be at rest. Now the actuality of that which can sound is just sound or sounding, and the actuality of that which can hear is hearing or hearkening; ‘sound’ and ‘hearing’ are both ambiguous. The same account applies to the other senses and their objects. For as the acting-and-being-acted-upon is to be found in the passive, not in the active factor, so also the actuality of the sensible [10] object and that of the sensitive subject are both realized in the latter. But while in some cases each has a distinct name, e.g. sounding and hearkening, in some one or other is nameless, e.g. the actuality of sight is called seeing, but the actuality of colour has no name: the actuality of the faculty of taste is called tasting, but the [15] actuality of flavour has no name. Since the actualities of the sensible object and of the sensitive faculty are one actuality in spite of the difference between their modes of being, actual hearing and actual sounding appear and disappear from existence at one and the same moment, and so actual savour and actual tasting, &c, while as potentialities one of them may exist without the other. The earlier students of [20] nature were mistaken in their view that without sight there was no white or black, without taste no savour. This statement of theirs is partly true, partly false: ‘sense’ and ‘the sensible object’ are ambiguous terms, i.e. may denote either potentialities [25] or actualities: the statement is true of the latter, false of the former. This ambiguity they wholly failed to notice.
If voice is a concord, and if the voice and the hearing of it are in one sense one and the same, and if concord is a ratio, hearing as well as what is heard must be a [30] ratio. That is why the excess of either the sharp or the flat destroys the hearing. (So also in the case of savours excess destroys the sense of taste, and in the case of [426b1] colours excessive brightness or darkness destroys the sight, and in the case of smell excess of strength whether in the direction of sweetness or bitterness is destructive.) This shows that the sense is a ratio.
That is also why the objects of sense are pleasant when e.g. acid or sweet or [5] salt, being pure and unmixed, are brought into the proper ratio; then they are pleasant: and in general what is blended—a concord—is more pleasant than the sharp or the flat alone; or, to touch, that which is capable of being either warmed or chilled:22 the sense and the ratio are identical; while excess is painful or destructive.
Each sense then is relative to its particular group of sensible qualities: it is [10] found in a sense-organ as such and discriminates the differences which exist within that group; e.g. sight discriminates white and black, taste sweet and bitter, and so in all cases. Since we also discriminate white from sweet, and indeed each sensible quality from every other, with what23 do we perceive that they are different? It must be by sense; for what is before us is sensible objects. (Hence it is also obvious that [15] the flesh cannot be the ultimate sense-organ: if it were, the discriminating power could not do its work without immediate contact with the object.)
Therefore discrimination between white and sweet cannot be effected by two agencies which remain separate; both the qualities discriminated must be present to something that is one and single. On any other supposition even if I perceived sweet and you perceived white, the difference between them would be apparent. What [20] says that two things are different must be one; for sweet is different from white. Therefore what asserts this difference must be self-identical, and as what asserts, so also what thinks or perceives. That it is not possible by means of two agencies which remain separate to discriminate two objects which are separate, is therefore obvious; and that it is not possible to do this in separate moments of time may be [25] seen if we look at it as follows. For as what asserts the difference between the good and the bad is one and the same, so also the time at which it asserts the one to be different and the other to be different is not accidental to the assertion (as it is for instance when I now assert a difference but do not assert that there is now a difference); it asserts thus—both now and that the objects are different now; the objects therefore must be present at one and the same moment. Both the discriminating power and the time of its exercise must be one and undivided.
But, it may be objected, it is impossible that what is self-identical should be [30] moved at one and the same time with contrary movements in so far as it is undivided, and in an undivided moment of time. For if what is sweet be the quality perceived, it moves the sense or thought in this determinate way, while what is bitter [427a1] moves it in a contrary way, and what is white in a different way. Is it the case then that what discriminates, though both numerically one and indivisible, is at the same time divided in its being? In one sense, it is what is divided that perceives two separate objects at once, but in another sense it does so qua undivided; for it is divisible in its being, but spatially and numerically undivided. [5]
But is not this impossible? For while it is true that what is self-identical and undivided may be both contraries at once potentially, it cannot be self-identical in its being—it must lose its unity by being put into activity. It is not possible to be at once white and black, and therefore it must also be impossible for a thing to be affected at one and the same moment by the forms of both, assuming it to be the case that sensation and thinking are properly so described.
Just as what is called a point is, as being at once one and two, properly said to [10] be divisible,24 so here, that which discriminates is qua undivided one, and active in a single moment of time, while qua divisible it twice over uses the same dot at one and the same time. So far then as it takes the limit as two, it discriminates two separate objects25 with what in a sense is separated; while so far as it takes it as one, it does so with what is one26 and occupies in its activity a single moment of time.
About the principle in virtue of which we say that animals are percipient, let [15] this discussion suffice.
3 · There are two distinctive peculiarities by reference to which we characterize the soul—(1) local movement and (2) thinking, understanding, and perceiving. Thinking and understanding are regarded as akin to a form of perceiving; for in [20] the one as well as the other the soul discriminates and is cognizant of something which is. Indeed the ancients go so far as to identify thinking and perceiving; e.g. Empedocles says27 ‘For tis in respect of what is present that man’s wit is increased’, and again28 ‘Whence it befalls them from time to time to think diverse thoughts’, and Homer’s phrase29 ‘For suchlike is man’s mind’ means the same. They all look [25] upon thinking as a bodily process like perceiving, and hold that like is understood as well as perceived by like, as I explained at the beginning of our discussion. Yet they [427b1] ought at the same time to have accounted for error also; for it is more intimately connected with animal existence and the soul continues longer in the state of error. They cannot escape the dilemma: either whatever seems is true (and there are some who accept this) or error is contact with the unlike: for that is the opposite of the [5] knowing of like by like.
But it seems that error as well as knowledge in respect to contraries is one and the same.
That perceiving and understanding are not identical is therefore obvious; for the former is universal in the animal world, the latter is found in only a small division of it. Further, thinking is also distinct from perceiving—I mean that in [10] which we find rightness and wrongness—rightness in understanding, knowledge, true opinion, wrongness in their opposites; for perception of the special objects of sense is always free from error, and is found in all animals, while it is possible to think falsely as well as truly, and thought is found only where there is discourse of reason. For imagination is different from either perceiving or discursive thinking, [15] though it is not found without sensatio
n, or judgement without it. That this activity is not the same kind of thinking30 as judgement is obvious. For imagining lies within our own power whenever we wish (e.g. we can call up a picture, as in the practice of [20] mnemonics by the use of mental images), but in forming opinions we are not free: we cannot escape the alternative of falsehood or truth. Further, when we think something to be fearful or threatening, emotion is immediately produced, and so too with what is encouraging; but when we merely imagine we remain as unaffected as persons who are looking at a painting of some dreadful or encouraging scene. Again [25] within the field of judgement itself we find varieties—knowledge, opinion, understanding, and their opposites; of the differences between these I must speak elsewhere.
Thinking is different from perceiving and is held to be in part imagination, in part judgement: we must therefore first mark off the sphere of imagination and then [428a1] speak of judgement. If then imagination is that in virtue of which an image arises for us, excluding metaphorical uses of the term, is it a single faculty or disposition relative to images, in virtue of which we discriminate and are either in error or not? The faculties in virtue of which we do this are sense, opinion, knowledge, thought.
[5] That imagination is not sense is clear from the following considerations: Sense is either a faculty or an activity, e.g. sight or seeing: imagination takes place in the absence of both, as e.g. in dreams. Again, sense is always present, imagination not. If actual imagination and actual sensation were the same, imagination would be [10] found in all the brutes: this is held not to be the case; e.g. it is not found in ants or bees or grubs. Again, sensations are always true, imaginations are for the most part false. Once more, we do not, when sense functions precisely with regard to its object, say that we imagine it to be a man, but rather when there is some failure of accuracy [15] in its exercise—then it is either true or false.31 And, as we were saying before, visions appear to us even when our eyes are shut. Neither is imagination any of the things that are never in error: e.g. knowledge or intelligence; for imagination may be false.
It remains therefore to see if it is opinion, for opinion may be either true or false.
But opinion involves belief (for without belief in what we opine we cannot have [20] an opinion), and in the brutes though we often find imagination we never find belief. Further, every opinion is accompanied by belief, belief by conviction, and conviction by discourse of reason, while there are some of the brutes in which we find imagination, without discourse of reason.32 It is clear then that imagination cannot, again, be opinion plus sensation, or opinion mediated by sensation, or a blend of [25] opinion and sensation; this is impossible both for these reasons and because the content of the supposed opinion cannot be different from that of the sensation (I mean that imagination must be the blending of the perception of white with the opinion that it is white: it could scarcely be a blend of the opinion that it is good with the perception that it is white): to imagine is therefore (on this view) identical with [428b1] the thinking of exactly the same as what one perceives non-incidentally. But what we imagine is sometimes false though our contemporaneous judgement about it is true; e.g. we imagine the sun to be a foot in diameter though we are convinced that it is larger than the inhabited part of the earth. Thus either while the fact has not changed and the observer has neither forgotten nor lost belief in the true opinion which he had, that opinion has disappeared, or if he retains it then his opinion is at [5] once true and false. A true opinion, however, becomes false only when the fact alters without being noticed.
Imagination is therefore neither any one of the states enumerated, nor compounded out of them.
But since when one thing has been set in motion another thing may be moved [10] by it, and imagination is held to be a movement and to be impossible without sensation, i.e. to occur in beings that are percipient and to have for its content what can be perceived, and since movement may be produced by actual sensation and that movement is necessarily similar in character to the sensation itself, this movement cannot exist apart from sensation or in creatures that do not perceive, [15] and its possessor does and undergoes many things in virtue of it, and it is true and false.
The reason is as follows. Perception of the special objects of sense is never in error or admits the least possible amount of falsehood. Next comes perception that what is incidental to the objects of perception is incidental to them: in this case [20] certainly we may be deceived; for while the perception that there is white before us cannot be false, the perception that what is white is this or that may be false. Third comes the perception of the common attributes which accompany the incidental objects to which the special sensibles attach (I mean e.g. of movement and magnitude); it is in respect of these that the greatest amount of sense-illusion is [25] possible.
The motion which is due to the activity of sense in these three modes of its exercise will differ; the first kind of derived motion is free from error while the sensation is present; the others may be erroneous whether it is present or absent, especially when the object of perception is far off. If then imagination presents no [429a1] other features than those enumerated and is what we have described, then imagination must be a movement resulting from an actual exercise of a power of sense.
As sight is the most highly developed sense, the name φαντασία (imagination) has been formed from φάoς (light) because it is not possible to see without light.
[5] And because imaginations remain in the organs of sense and resemble sensations, animals in their actions are largely guided by them, some (i.e. the brutes) because of the non-existence in them of thought, others (i.e. men) because of the temporary eclipse in them of thought by feeling or disease or sleep.
About imagination, what it is and why it exists, let so much suffice.
[10] 4 · Turning now to the part of the soul with which the soul knows and (whether this is separable from the others in definition only, or spatially as well) we have to inquire what differentiates this part, and how thinking can take place.
If thinking is like perceiving, it must be either a process in which the soul is acted upon by what is capable of being thought, or a process different from but [15] analogous to that. The thinking part of the soul must therefore be, while impassible, capable of receiving the form of an object; that is, must be potentially identical in character with its object without being the object. Thought must be related to what is thinkable, as sense is to what is sensible.
Therefore, since everything is a possible object of thought, mind in order, as Anaxagoras says, to dominate, that is, to know, must be pure from all admixture; [20] for the co-presence of what is alien to its nature is a hindrance and a block: it follows that it can have no nature of its own, other than that of having a certain capacity. Thus that in the soul which is called thought (by thought I mean that whereby the soul thinks and judges) is, before it thinks, not actually any real thing. For this [25] reason it cannot reasonably be regarded as blended with the body: if so, it would acquire some quality, e.g. warmth or cold, or even have an organ like the sensitive faculty: as it is, it has none. It was a good idea to call the soul ‘the place of forms’, though this description holds only of the thinking soul, and even this is the forms only potentially, not actually.
Observation of the sense-organs and their employment reveals a distinction [30] between the impassibility of the sensitive faculty and that of the faculty of thought. After strong stimulation of a sense we are less able to exercise it than before, as e.g. [429b1] in the case of a loud sound we cannot hear easily immediately after, or in the case of a bright colour or a powerful odour we cannot see or smell, but in the case of thought thinking about an object that is highly thinkable renders it more and not less able afterwards to think of objects that are less thinkable: the reason is that while the [5] faculty of sensation is dependent upon the body, thought is separable from it.
When thought has become each thing in the way in which a man who actually knows is said to do s
o (this happens when he is now able to exercise the power on his own initiative), its condition is still one of potentiality, but in a different sense from the potentiality which preceded the acquisition of knowledge by learning or discovery; and thought is then able to think of itself.33
Since we can distinguish between a magnitude and what it is to be a [10] magnitude, and between water and what it is to be water, and so in many other cases (though not in all; for in certain cases the thing and its form are identical), flesh and what it is to be flesh are discriminated either by different faculties, or by the same faculty in two different states; for flesh necessarily involves matter and is like what is snub-nosed, a this in a this. Now it is by means of the sensitive faculty that we discriminate the hot and the cold, i.e. the factors which combined in a certain ratio [15] constitute flesh: the essential character of flesh is apprehended by something different either wholly separate from the sensitive faculty or related to it as a bent line to the same line when it has been straightened out.
Again in the case of abstract objects what is straight is analogous to what is snub-nosed; for it necessarily implies a continuum: its constitutive essence is different, if we may distinguish between straightness and what is straight: let us take it to be two-ness. It must be apprehended, therefore, by a different power or by [20] the same power in a different state. To sum up, in so far as the realities it knows are capable of being separated from their matter, so it is also with the powers of thought.