LECTIO ONE

             § 564. Here begins Book III in the Greek text; for the good reason, apparently, that it is here that Aristotle begins to examine the intellect. Now there have been philosophers who denied all difference between intellect and senses. But clearly the intellect cannot be any one of the exterior senses already considered; for its apprehension is not restricted to any one particular class of sense-objects. So the question is whether sensitivity includes any other cognitive faculty such as might lend support to the view that intellect is somehow one of the senses.

             § 565. This section divides into three. First, he asks whether there is any other sense besides the five exterior senses. Next, at 'Now, if the soul is defined', he proves that the intellect is entirely distinct from the senses. Thirdly, at 'As to the part of the soul', he examines the intellectual part of the soul, by now clearly distinguished from the senses. The first of these sections has two parts: (a) he shows that there are no other particular senses besides the five exterior ones; and (b) he shows that, besides these, there is a common sense,--this comes at 'Since we perceive that we see'. With regard to (a), after proving that there are only five particular senses, he shows why there are several of them and not one only. The former proof itself divides into two: first he shows that only the five senses apprehend particular 'sensibles'; and then at 'But there cannot be', that the same five are the only senses to apprehend common 'sensibles'.

             § 566. To prove the first of these two points he argues thus. If a subject has a sense-organ in virtue of which a certain definite range of sensible objects is naturally perceptible, this organ is the medium by which it perceives those objects. But the higher animals are endowed with all the organs of sense; therefore they can perceive the entire range of sensible objects; and as these organs are only five in number, the whole range of particular sensible objects is covered by the five organic senses.

             § 567. In proposing this argument Aristotle begins by stating his purpose in using it, i.e. to convince anybody that there are no other senses besides the five aforesaid.

             § 568. Next at 'For if . . .', he explains the major premiss of the argument: that a subject possessed of any sense organ can know all that can be known by that organ. This he shows from the sense of touch. There are obviously certain tangible qualities, namely (as has been said) the various modifications of elemental bodies as such; for what has been said about the four elements has made it clear that there are such modifications. And all these tangible qualities, as such, fall within the range of our sensation.

             § 569. He then applies the same principle--that we are aware of precisely such objects as correspond to a given sense-organ in us--to the other senses. So he says: if we sense anything tactually perceptible, so that all tangible qualities, as such, are sensed by us, we can go on to argue in general that, if we do not in fact perceive a sensible quality, the reason must be that we lack the sense-organ to which it corresponds; precisely because if we have a sense-organ we do perceive certain sensible qualities. And this generalisation he then supports with particular examples.

             § 570. And first with respect to things we apprehend without any extrinsic medium; for he says that whatever we sense 'by contact', i.e. without an extrinsic medium, is reached by the organ of touch (under which he includes taste). But where, as in the other senses, certain extrinsic media, simple substances like air and water, come between us and the object, it is relevant to observe that one and the same organ may convey apprehensions of several objects different in kind; and in that case, the subject having the organ apprehends things different in kind. For example, if a sense-organ contains air, and air naturally retains and conveys both colour and sound, then a subject with an air-containing organ will be able to sense both colour and sound. If, on the contrary, several different organs can attain the same sensible object--as happens in the case of organs composed, the one of air, the other of water, which are both transparent and therefore both receptive of colour,--then a subject with any one of such organs is able to perceive whatever is perceptible through, or by means of, all of them. The reason for his saying this is that the sense-organs which function through an extrinsic medium always correspond to that medium; and the fact is that the same sensible object, for instance odour, can reach different animals through different media, e.g. through water as well as air.

             § 571. Thirdly, at 'The sense-organs are formed', he makes and explains a further statement: that the higher animals possess all the organs of sense. These organs, he says, are by nature composed of only two of the simple bodies, namely air and water--these being the two most passive simple bodies, and a ready passivity to the sensible object being the condition required in a sense-organ. Thus the pupil of the eye contains water, enabling the eye to receive a likeness of the thing it sees; the organ of hearing contains air (as we have noted already); whilst the sense of smell is related by some to air and by some to water. Fire, on the other hand, by reason of its extreme activity, plays no part in the organs of sense, though in a certain way its presence is felt in all the senses; for sensitivity always presupposes warmth because it always presupposes life.

             § 572. Whilst earth as such has nothing to do with the sense-organs as such, it is in a special way a condition of touch: for it is mixed in with the body in a certain definite proportion which itself determines that mean between tangible extremes which gives the body a sense of touch at all; whence it follows that the organ of touch contains all the elements mixed in a certain proportion. But precisely as sensitive the sense-organs are made of air and water and of these only; and the air or water-composed organs are found in those animals we call 'higher animals'. So he concludes by saying that, apart from naturally inferior organisms, such as the immobile animals which have only the sense of touch, all animals are endowed with all the organs of sense.

             § 573. Apart, too, from the 'defective', i.e. animals lacking a sense which should be theirs by nature, like blind or deaf men. But moles, for example, are 'higher animals', having eyes under their skin. Living underground they do not need sight; and if their eyes were uncovered the soil would aggravate them.

             § 574. Clearly this argument assumes a definite number of elements. It infers that, because there are only so many elements, the sense-organs that reach their objects through an exterior medium must be composed exclusively of air and water. Again, it presumes a fixed number of elemental qualities which are also the tangible qualities; and infers that all the latter are known to us; and that therefore we are equipped with all the sense faculties that exist. These conclusions could only be disproved by showing, either that there was some other corporeal element besides the four known to us, or that there were other tangible qualities (in the things around us and known to us), other than those which we do in fact perceive by touch. But there is no need to entertain such hypotheses, and we can safely conclude that the five senses we possess are the only senses that exist.

             § 575. Then where he says, 'But there cannot be', he rejects the suggestion that the 'common sensibles' are the object of another and distinct sense. For the proper and direct object of any one sense is only known indirectly by any other sense; but the common sensibles are not known indirectly by any sense at all; rather, they are each directly known by several senses. Therefore they cannot be the proper objects of any one sense.

             § 576. Note how this argument proceeds. Aristotle first states the conclusion, that there cannot be any one organ specially adapted to the perception of the 'common sensibles' perceived directly, not indirectly, by all the senses, namely movement, rest and so forth.

             § 577. Then, at 'For we know', he shows that these common sensibles are directly, not indirectly, perceived. What enters sensation precisely by disturbing the sense-organ is directly, not indirectly, sensed; for to sense directly is simply to receive an impression from a sensible object. Now all these common sensibles are sensed in this way, which is why he says that we apprehend them by 'motion', i.e. through some disturbance of the organ. Size, for example, is obviously sensed in this way: it is the subject of such sensible qualities as colour or savour, and no quality is able to act in separation from its subject. From which it follows that shape also is known in this way, for shape is an aspect of size; it is size as terminated. As Euclid says, shape is what is contained in a limit.

             § 578. Rest also is perceived by means of movement, as darkness by means of light, for rest is the lack of movement. Number also, since it comes from dividing a continuum or continuous magnitude, is apprehended as the latter's negation, and its properties are known through those of the continuum; for as the continuum is infinitely divisible, so numbers can go on to infinity, as is shown in Book III of the Physics. Now it is clear that all the objects of any sense go to make up one single direct object of that sense, in so far as they concur in affecting the organ of that sense; whence it follows that these 'common sensibles' belong to the direct, not the indirect, objects of sensation; and further, that no one of them is the object of any distinct and special sense.

             § 579. Then, at 'The situation etc.', he shows that if they were the object of any special sense they would be also indirectly sensed. This is what he means by saying that the hypothesis in question would imply that we perceived the common sensibles in the same way as we see sweetness. For sweetness and (e.g.) whiteness each answer to a distinct and special sense; hence, when both qualities are found in the same thing each is known directly by its own special sense and indirectly by that of the other. By sight we know whiteness directly, sweetness indirectly.

             § 580. But if an object is not directly perceived by any special distinct sense it can never become the indirect object of any other sense through the concurrence of two senses or sensibles in the same thing; it must always, in every respect, be indirectly perceived. Thus I perceive indirectly that so and so is Cleon's son, not because he is Cleon's son, but because he is white; whiteness as such only happens to be connected with Cleon's son. Being the son of Cleon is not (like sweetness) indirectly visible in such a way as to imply its being directly perceived by some other sense. On the other hand the common sensibles are not indirectly sensible at all; they are a common yet direct object of several distinct senses. It follows that they answer to no special and distinct sense; if they did, they would be indirectly sensed, like the fact that so and so was Cleon's son.

             § 581. For the senses perceive each other's special objects indirectly, as sight that of hearing, and vice versa. Sight does not perceive the audible as such, nor hearing the visible as such (for the eye takes no impression from the audible, nor the ear from the visible) but both objects are perceived by each sense only in so far as 'one sense', i.e. one actual sensation so to say, bears upon an object which contains both. I mean that both the senses in question are exercised at once upon one and the same sensible thing, as when bile is at once seen as red and tasted as bitter; so that as soon as we see that this thing is red we judge that it is bitter. But there is no special sense of the conjunction of redness and bitterness, for this conjunction is quite incidental, and what is incidental cannot be the object of any special faculty. And the fact that sight only indirectly knows savour helps us to understand why we are so often deceived in such cases, and jump to the conclusion that because a certain thing is, for example, red, it is therefore bile.

             § 582. Then at 'One might ask', he goes on to enquire why there are many senses. As this is a question about a species as a whole it must be answered in terms of final causality (as he explains towards the end of the De Generatione Animalium); not, like questions about individual peculiarities, in terms of material or efficient causality. So here he introduces the idea of purpose. The question might arise, he says, why we have several senses instead of only one; and he answers that it is to enable us to discern such things as movement, size and number, which are at once accompaniments of each distinct and proper sensible object and also common to them all. For suppose there were only the sense of sight, whose proper object is simply colour; then, since the impression of colour on the sense-organ immediately involves an impression of size, so that the two objects are inseparable, we should never be able to distinguish between colour and size; they would appear to us as exactly the same. But the fact that size is also perceived by a sense other than sight, whilst colour is not, is enough to show us that size and colour are not the same. And the same holds good for the other common sensibles.

             § 583. To this one might add also the following reason. Since every potency as such implies an object, there must be a diversity of sensitive potencies if, and in the manner that, there is a diversity of sensible objects. But objects become sensible by impressing a sense-organ; hence to the different kinds of such impressions will correspond a diversity of sensitive potencies. Now one way in which the sense-organ is impressed by objects is by physical contact, whence arise both the sense of touch, perceiving what composes the physical constitution of an animal, and the sense of taste, perceptive of those qualities which indicate the suitability of an animal's nourishment for keeping its body in being. And another way by which the sense-organ can receive its impression is through a medium; and this involves either an intrinsic change in the object itself, as in the case of smell, which implies a certain disintegration of the thing smelt; or a change of place, as in the case of sound; or no change at all in the sensible object, but simply a spiritual impression upon the medium and the sense-organ, such as is made by colour.

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