LECTIO TEN

             § 350. After treating of the vegetative part of soul the Philosopher now begins to examine the sensitive part. This treatment divides into two sections, the first of which deals with what is most apparent in sensitivity, i.e. the exterior senses, while the second, beginning at 'That there is no other sense', treats of what is latent therein. In the former section Aristotle first explains how sense-faculties are related to sensible objects, and then, at 'In treating of each sense' he defines both faculty and object. Regarding the former point, he first repeats some earlier observations, and then, at 'It may be asked', proceeds to the present problem.

             First of all, then, he remarks that this is the place to start discussing the sensitive soul, beginning with a general view of the subject and going on later to a more detailed treatment. And he repeats two things already said: that to sense is to be moved or acted upon in some way, for the act of sensation involves a certain alteration of the subject; and secondly, that it was the view of some enquirers that the passivity of sensation was an instance of like being acted upon by like.

             § 351. For some early thinkers held that like is known and sensed by like: as Empedocles said, earth knows earth, fire knows fire, and so on. Now the general problem of the action of like upon like is discussed in the De Generatione, where Aristotle's conclusion is that, although at the start of any action the agent and patient are contrary, when the action is finished they are similar. For the agent, in acting, assimilates the patient.

             § 352. Then, at 'It may be asked', he proceeds to the present problem. He shows that in themselves the senses are in potency; then, at 'But since we speak of sensing in two ways', that they are sometimes in act; and thirdly, at 'Distinctions however', he shows how they move from potency into act.

             To understand the first of these three points, note that all who, like Empedocles, said that like was known by like, thought that the senses were actually the sense-objects themselves,--that the sensitive soul was able to know all sense-objects because it consisted somehow of those objects; that is, of the elements of which the latter are composed.

             § 353. Two things follow from this hypothesis. (1) If the senses actually are, or are made up of, the sense-objects, then, if the latter can be sensed, the senses themselves can be sensed. (2) Since the presence of its object suffices to enable the sense-faculty to sense, then, if this object actually exists in the faculty as part of its composition, it follows that sensation can take place in the absence of external objects. But both these consequences are false. He introduces them here as specimens of the problems which the early philosophers could not solve. So he says, 'It may be asked why there is no sensation of the senses', i.e. why the senses themselves are not sensed; for it seems they would be sensed if they, the faculties, were really like their objects.

             § 354. It is also hard to see 'why they do not produce sensation', i.e. why actual sensation does not occur, 'without something extraneous', i.e. without exterior sense-objects; since, in the opinion of the ancients, fire, earth and the other elements belong to the inner nature of the sense-faculty and are perceptible by sense, either in themselves, i.e. in their essence (as these philosophers thought, not distinguishing between the senses and the intellect which alone perceives essence), or in the accidental qualities proper to them, namely heat and cold and so forth, which are essentially sense-perceptible. Now since these difficulties are insurmountable if the sense-faculty consists of its objects in their actuality (as the early philosophers thought), Aristotle concludes that the sensitive soul is clearly not actually, but only potentially, the sense-object. That is why sensation will not occur without an exterior sense-object, just as combustible material does not burn of itself, but needs to be set on fire by an exterior agent; whereas if it were actually fire it would burn simply by itself.

             § 355. Then, at 'But as we speak of sensing', he shows, by the two ways in which we speak of anyone sensing, that sensation is intermittently actual. For we sometimes say that a man sees or hears when he only does these things potentially, as when he is asleep; but sometimes we mean that what he is actually doing is seeing or hearing. Clearly, then, sensation and sensing may be referred to either in act or in potency.

             § 356. Next, at 'To start with then,' he explains the above. For to speak of sensation as 'in act' might seem contradictory to his previous statement that it was a certain passive being acted upon or moved; for to be in act seems to pertain to an active agent. So he explains that in calling sensation an 'act' he is referring precisely to the state of being acted upon or moved; inasmuch as this is a certain state of being actual. For movement has a certain actuality; which is the actuality (as he says in the Physics, Book III) of the imperfect or potential, that is to say, of changeable being. In the same way, being moved and sensation itself are a sort of action, as implying an actuality of being. The phrase 'To start with', however, means that he will add something later to show how the senses become actual in fact.

             § 357. Thirdly, at 'All things are moved and affected', he shows how it follows from the above that the old theory that like senses like cannot be true. Everything potential, he says, is acted upon and moved by some active agent already existing; which in its actualising function makes the potential thing like itself. In some sense, then, a thing is acted upon by both its like and its unlike (as we have already remarked). At first, and while the transforming process is going on, there is dissimilarity; but at the end, when the thing is transformed and changed, there is similarity. And so it is as between the sense-faculty and its object. And the early philosophers went wrong because they missed this distinction.

417a 22-417b 17

SENSITIVITY

POTENCY AND ACT CONTINUED

             DISTINCTIONS however must be made concerning potency and act; for at present we are speaking of these in one sense only.§ 358

             For there is such a thing as 'a knower', in one sense, as when we say that man is 'a knower' because man is of the class of beings able to have knowledge. But also as when we speak of a man as 'knowing' because he possesses the science of grammar. These two are not capable in the same way; but the former's power is, as it were, generic and comparable to matter; whereas the latter has the power to consider at will so long as no extraneous obstacle intervenes. Yet again, only he who is actually attending to (say) the letter A, is in the strictest sense knowing.§§ 359-61

             Therefore the first two are knowing in potency. But one has undergone a change through being taught, and is often altered from the contrary state, whereas the other is moved to action from simply having sense or grammar without acting [accordingly]; but in a different way from formerly when he had not yet acquired any habit [of knowing]. § 362-4

             Nor is 'being acted on' a simple term. It is one thing to be somehow destroyed by a contrary; quite another when what is in potency is maintained by what is in act, and is of a similar nature, being related to the latter as potency to act.§§ 365-6

             For when a man possessed of knowledge becomes actually thinking, there is certainly either no 'alteration'--there being a new perfection in him, and an increase of actuality;--or it is some novel kind of alteration. Hence it is as misleading a statement to say that a man is 'altered' when he thinks, as to say this of the builder when he builds. The process from being in potency to understand and think to actually doing so should not be called instruction, but has by rights some other name.§§ 367-8

             The change from being in potency, in one who learns and receives instruction from another (who actually has learning and teaches) either should not be called a 'being acted upon' (as we have said), or there are two modes of alteration, one a change to a condition of privation, the other to possession and maturity.§§ 369-72