LECTIO THREE

             § 599. So far the Philosopher's approach to an examination of the 'common sense' has been by way of our perception of our own seeing and hearing. But his scrutiny of this perception has so far only led him to the conclusion that seeing is itself perceived by the faculty of sight, though not in the same way as exterior objects are perceived. He has not yet decided that there is any one common faculty that takes account of the activities of the particular senses. But now he takes his enquiry a step further by pointing to another activity of the soul as evidence of the existence of a faculty with a common relationship to all the five senses: the activity of discriminating between various sense-objects. And here he does two things: first, he shows how far the particular senses can so discriminate; next, he investigates that discrimination of sensible objects which exceeds the scope of any particular sense (this begins at 'Since we distinguish').

             § 600. He observes then, first, that we have seen that each sense is perceptive of its own proper object precisely in so far as a likeness of the object is formed within its own particular organ as such; for the organ of each sense is directly, not indirectly, impressed by the proper object of that sense. And within this proper object each sense discerns its characteristic differences; sight, e.g. discerning white and black, taste sweet and bitter; and so with the others.

             § 601. Then, at 'Since we distinguish', he points out the faculty that discriminates, as the particular senses cannot discriminate, between the objects of the different senses. And here he does two things: first, he demonstrates his conclusion; then he puts and solves an objection (at 'But it is impossible etc.'). The demonstration has three parts: (a) he shows that there is a sense that perceives the differences between black and white and sweet; (b) that this sense is one faculty, not two; and (c) that it simultaneously perceives both objects between which it discriminates. First, then, he observes that whereas we are able to distinguish not only between black and white, or sweet and bitter, but also between white and sweet, and indeed between any one sense-object and another, it must be in virtue of some sense that we do this, for to know sense-objects as such is a sensuous activity; the difference between white and sweet is for us not only a difference of ideas, which would pertain to the intellect, but precisely a difference between sense-impressions, which pertains only to some sense-faculty.

             § 602. If this be true, the most likely sense-faculty would seem to be touch, the first sense, the root and ground, as it were, of the other senses, the one which entitles a living thing to be called sensitive. But clearly, if this discrimination were a function of touch, then the fundamental organ of touch would not be flesh; if it were, then by the mere contact of flesh and a tangible object, this object would be discriminated from all other sense-objects. Now this discrimination cannot be attributed to touch precisely as a particular sense, but only as the common ground of the senses, as that which lies nearest to the root of them all, the 'common sense' itself.

             § 603. Then, at 'Nor could etc.', he shows that it is by one and the same sense that we distinguish white from sweet. For one might have supposed that we did it by different senses, by tasting sweetness and by seeing whiteness. But if this were true, he says, we could never perceive that white was other than sweet. If this difference is to appear it must appear to some one sense-faculty; so long as white and sweet are sensed by distinct faculties it is as though they were sensed by two different men, one perceiving sweet and another white; I this and you that. In this case sweet and white are obviously distinct, because I am impressed in one way by sweetness, and you in another by whiteness.

             § 604. But this would not show us their sensible difference. There must be one single faculty which 'says' that sweet is not white, precisely because this distinction is one single object of knowledge. The 'saying' is the expression of an inward knowing; and as the saying is a single act, it must spring from a single act of understanding and sensing that what is sweet is not white. He says 'understands and senses', either because he has not yet established the distinction between sense and intellect, or perhaps because both these powers know the difference in question. As then the man who judges white to be other than sweet must be one man aware of both objects, so he must do this by means of one faculty; for awareness is the act of a faculty. Hence Aristotle's conclusion, that it is clearly impossible to perceive 'separate objects', i.e. that two things are distinct, by 'separate', i.e. by distinct, means; there must be one single power aware of both things.

             § 605. Next, at 'And the same', he proves that this awareness is of both things simultaneously, not at 'separate', i.e. distinct, moments. This will appear, he says, from what follows; for as a judgement on the difference between things is single with respect to what is discerned, for example that good is distinct from bad, so is it single with respect to the time in which it is discerned. One judges that such and such a difference exists when one is judging. Nor is the time only accidentally connected with the difference itself, as it would be if 'when' referred to the subject judging and the meaning was 'he now judges that a difference exists' (and not ' . . . that now a difference exists'); in which case the 'now' would be merely incidental to the object. But the judgement of difference is in the present in the sense that there is difference at present; which necessarily implies a simultaneous apprehension of the two different objects; they are both known in the same instant as they are known to be different. Obviously, then, they are known at once and together. Hence, as one undivided faculty perceives the object's difference, so in one undivided moment both are apprehended.

             § 606. However, he now puts an objection to himself;--concerning which he does four things. First, he states the objection, as follows. One and the same indivisible thing cannot move in different directions in one and the same indivisible moment of time. Now intellect and sense are moved by their objects, the one by an intelligible thing to understand it, the other by a sensible thing, to sense it. But distinct and mutually exclusive sense-objects cause distinct and mutually exclusive movements; therefore one and the same sensitive or intellectual faculty cannot know several distinct and mutually exclusive objects at the same time.

             § 607. Then, at 'Therefore what', he suggests the following solution. That which perceives the difference between mutually exclusive objects does so simultaneously and is numerically indivisible, i.e. it is one as a subject of actions; but in its essence, and therefore to thought, it is divided. So, then, it is in one way an indivisible subject which perceives 'divided', i.e. distinct objects; but in another way, the percipient subject is itself divisible, inasmuch as in essence, and to thought, it is divisible--even while it does not cease to be locally and numerically one indivisible subject of actions. He says 'locally' referring to the fact that different faculties are found in different parts of the body.

             § 608. Thirdly, at 'But this is not possible', he rejects this solution: because if a thing really is a self-identical and indivisible subject, even if it is not so in thought, it can indeed be in potency to diverse movements, but once it is actually 'in activity' or moving, it cannot do so in mutually exclusive ways; for this implies a real divisibility. One and the same indivisible thing cannot be white and black at the same time in the same respect; nor, for the same reason, can it receive simultaneous impressions from white and black objects. And the same is true of understanding and sensing, if these are a kind of reception of impressions.

             § 609. Fourthly, at 'But it is just as', he gives the true solution, using the simile of a point. Any point between the two ends of a line can be regarded either 'as one or two'. It is one as continuing the parts of the line that lie on either side of it, and so forming the term common to both. It is two inasmuch as we use it twice over, to terminate one part and begin the other. Now sensitivity flows to the organs of all the five senses from one common root, to which in turn are transmitted, and in which are terminated, all the sensations occurring in each particular organ. And this common root can be regarded from two points of view: either as the common root and term of all sensitivity, or as the root and term of this or that sense in particular. Hence, what he means is that just as a point, under a certain aspect, is not one only but also two, or divisible, so the principle of sensitivity, if regarded as the root and term of seeing and of hearing, appears twice over under the same name, and in this way it is divisible.

             § 610. In so far then as this single principle receives and 'takes account of two distinct' and separate 'objects', these are known 'as in a separate', i.e. as by a divisible 'principle' of knowledge; 'but in so far as' it is single in itself it is able to know these objects and their differences together and simultaneously. It is a common sensitive principle, aware of several objects at once because it terminates several organically distinct sensations; and as such its functions are separate. But just because it is one in itself it discerns the difference between these sensations.

             § 611. Now all sensuous activity being organic, this common sensitive principle must have its organ; and since the organ of touch is all over the body it would seem to follow that, wherever the ultimate root of the organ of touch may be, there also is the organ of the common sensitive principle. It was with this in mind that Aristotle has said that if flesh were the fundamental organ of touch, we should discriminate between various sense-objects by merely touching things with our flesh.

             § 612. We may note also that though this common principle is set in motion by the particular senses, all the impressions of which are transmitted to it as to their common term, this does not imply that the particular senses are nobler than the common sense; though certainly a mover or agent is, as such, nobler than what it moves or acts upon. Nor is the exterior sensible object nobler, strictly speaking, than the particular sense moved by it, though it is in a way nobler as having actually the white or sweet quality which the senses have only potentially; but of the two the sense is strictly the nobler thing, and this in virtue of sensitivity itself--hence in receiving the object immaterially it ennobles it, for things received take, as such, the mode of being of the receiver. And the common sense receives its object in a still nobler way because it lies at the very root of sensitivity, where this power has its point of greatest unity. Yet we must not suppose that the common sense appropriates actively the impressions received in the sense-organs; all sensitive potencies are passive; and no potency can be both active and passive.

             § 613. Observe too that each particular sense is able to discriminate between contrary sense-objects in virtue of its share in the power of the 'common sense'; each is one of the terminal points for the various influences which reach us from mutually exclusive exterior sense-objects through a medium. But the final judgement and discrimination belong to the 'common sense'.

             § 614. Concluding, he says that he has now discussed the principle according to which an animal is said to have, or be able to have, sensations.

427a 16-427b 26