LECTIO ELEVEN

             § 358. Having explained how the sensitive faculties are both in act and in potency, the Philosopher now goes on to say how they are brought from potency into act. This he does in two parts: first distinguishing between act and potency, and between the diverse ways in which a thing may pass from one state to the other, taking his example from the intellect; and secondly, at 'The first change in the sensitive being', he applies all this to the case of sensation.

             As regards the first of these parts he does three things: (a) he states his intention; (b) he distinguishes, at 'For there is such a thing as', between act and potency in the intellect; and (c) he explains, at 'Therefore the first two', how what is potential, in both the two senses of the term which have been distinguished, becomes actual.

             First of all, then, he says he is about to discuss potency and act, in order to show the diverse ways in which things can be said to be actual or potential--because so far the two terms have been used 'in one sense only', i.e. without distinctions.

             § 359. Then at 'For there is such a thing as', he distinguishes act and potency in the intellect. We speak, he says, in one sense of potency when we say that man is a knower, referring to his natural capacity for knowledge. Man, we say, is one of that class of beings that know or have knowledge, meaning that his nature can know and form habits of knowing. In another sense, however, we say of someone that he knows, meaning that he knows certain definite things; thus we say of one who has the habit of some science--e.g. Grammar--that he is now one who knows.

             § 360. Now, obviously, in both cases the man's capacities are implied by calling him a knower; but not in the same way in both cases. In the first case man is said to be 'able' through belonging to a certain genus or 'matter', i.e. his nature has a certain capacity that puts him in this genus, and he is in potency to knowledge as matter to its form. But the second man, with his acquired habit of knowing, is called 'able' because when he wishes he can reflect on his knowledge--unless, of course, he is accidentally prevented, e.g. by exterior preoccupations or by some bodily indisposition.

             § 361. A third case would be that of a man who was actually thinking about something here and now. He it is who most properly and perfectly is a knower in any field; e.g. knowing the letter A, which belongs to the above-mentioned science of Grammar. Of the three, then, the third is simply in act; the first is simply in potency; while the second is in act as compared with the first and in potency as compared with the third. Clearly, then, potentiality is taken in two senses (the first and second man); and actuality also in two senses (the second and third man).

             § 362. Then where he says 'Therefore the first two', he explains (1) how both these types of potency are actualised, and (2), at 'Nor is being acted on', he discusses whether this actualisation is the result of a being acted upon.

             First, then, he remarks that while in the two first cases there is potential knowledge, and while potency as such is able to be actualised, there is a difference, in respect of actualisation, between a primary and a secondary potency. One in primary potency to knowledge is brought into act through being, as it were, changed or altered by teaching received from another (the teacher) who already knows actually. And often, he says, this change is from a contrary habit; alluding to those who come to actual knowledge from a state of ignorance.

             § 363. Ignorance has two meanings. It can be purely negative: when the ignorant person neither knows the truth nor is involved in the opposite error; and in this case he is simply brought into actual knowledge, not changed by being rid of a contrary habit. On the other hand, ignorance may imply the bad condition of being involved in error contrary to the truth; and to acquire knowledge, then, one must be changed by being delivered from that contrary habit.

             § 364. But one in potency in the secondary sense--i.e. as already possessing the habit--passes from the state of having, indeed, sensations or knowledge but not exercising them, into the state of actually knowing something here and now. And this kind of actualisation differs from the other.

             § 365. Then at 'Nor is being acted on' he discusses the question whether both kinds of actualisation can be called being acted upon. First, he explains the different meanings of 'being acted on'. Then at 'For when a man possessed of etc.', he applies these distinctions to the present problem. First, then, he remarks that being acted upon has several meanings, like potency and act. In one sense it implies some kind of destruction caused by a contrary quality. For in the strict sense the state of being passive to action seems to connote, on the side of the patient, a loss of something proper to it through its being overcome by the agent; and this loss is a sort of destruction, either absolutely, as when the patient loses its substantial form, or relatively, as in the loss of an accidental form. And the loss implies a contrariety in the agent, the imposition upon the patient's matter, or being, of a contrary form from outside. In the first and strict sense, then, 'being acted on' means a destruction caused by a contrary agent.

             § 366. In another and looser sense the term connotes any reception of something from outside. And as a receiver is to what it receives as a potency to its actuality; and as actuality is the perfection of what is potential; so being acted upon in this sense implies rather that a certain preservation and perfection of a thing in potency is received from a thing in act. For only the actual can perfect the potential; and actuality is not, as such, contrary to potency; indeed the two are really similar, for potency is nothing but a certain relationship to act. And without this likeness there would be no necessary correspondence between this act and this potency. Hence potency in this sense is not actualised from contrary to contrary, but rather from like to like, in the sense that the potency resembles its act.

             § 367. Next at 'When a man possessed of', Aristotle discusses whether the actualising of already acquired knowledge involves a being acted upon. And he takes first the transit from secondary potentiality into fullest actuality; and then at 'The change from being in potency', that from primary potentiality into the acquired habit of knowledge. Now, as to the former point, he asserts that this movement into actual thinking is not truly a passive being altered; for, as we have seen, no movement into act, as movement into act, is such. The term applies, strictly, only to the alteration of a subject from one to the other of two mutually exclusive qualities. But this is not what happens when a man begins to exercise his mind on knowledge he already possesses; rather, he is developing a quality already possessed; as Aristotle says here, it is 'a new perfection in him and an increase of actuality'; for perfection increases with actuality. And if one insists on using the terms 'actuality' and 'being acted upon', they must be taken in a wider and less strict sense. And to illustrate the point he adds that it is just as inept to speak of a thinker being 'altered' when he actually thinks as to say of a builder that he is altered by building.

             § 368. A further conclusion: if it be granted that to pass from habitual to actual knowing is not a reception of new knowledge, but rather a drawing out and perfection of knowledge possessed already, it remains true that to be taught is to acquire new knowledge. Therefore, when a man is brought simply to the act of knowing or understanding, this ought not, strictly speaking, to be called 'instruction'; it might be given some other name, though perhaps no other has in fact been found for it.

             § 369. Then at 'The change from being in potency', he discusses whether the transit from potency to act of one who acquires completely fresh knowledge is an 'alteration', in the sense of a 'being acted upon'. He says that when a learner, previously knowing only potentially, is instructed by a master already knowing actually, one should either call this simply not a case of alteration and being acted upon, or else distinguish two kinds of alteration. The one kind is 'a change to a condition of privation', i.e. into qualities opposed to those which the thing already has, and incompatible with these, and therefore until now excluded by them. The other kind is 'by a change to a possession and maturity', i.e. through receiving habits and forms which perfect the thing's nature and involve no loss of what it already has. And the learner is altered in this second sense, not in the first.

             § 370. Now this seems to contradict what was said above, that learners often changed from a contrary habit, and thus, it would seem, acquired qualities opposed to their former ones. But really, when one is brought from error to the knowledge of truth there is indeed a certain likeness to the change from one quality to its opposite, but it is only a likeness. For where there is true alteration both the opposed qualities--the terms of the process--are necessarily and essentially involved, e.g. becoming white involves not only white, but also black, or some intermediary colour which in relation to white is a sort of blackness. But where knowledge is acquired it is quite accidental that the learner was previously in error. He could learn without first being in error. Hence it is not in the true sense an alteration.

             § 371. Another difficulty occurs where he says that the learner as such is taught by a master who already knows. For it does not always happen thus; a man may acquire knowledge by finding out for himself To this we reply that whenever a potential knower becomes an actual knower, he must indeed be actualised by what is already in act. But this may be effected either by a purely extrinsic cause, as when air is lit up by an already actual light, or by an intrinsic cause as well, as when a man is healed both by nature and by a doctor. In this latter case both causes of hearing are actual health; for obviously health exists both in the mind of a doctor and in some healthy part of the man's nature (i.e. the heart) in virtue of which the rest of the man recovers health. Doctors make use of such natural means to health as warmth or cold or other variable dispositions, so that we can say that the whole of their skill consists in helping nature to drive out sickness. If nature were strong enough she could do this by herself without a doctor's aid.

             § 372. And the case is the same when a man acquires knowledge. For here again there are two principles involved: an intrinsic one, which a man uses when he finds things out for himself; and an extrinsic one, as when he learns from others. But in both cases a potency is actualised by something already in act. The light of the agent intellect gives a man immediate actual knowledge of the first principles which we know by nature, and in virtue of this actual knowing he is led to actual knowledge of conclusions previously known by him only potentially. In like manner too a teacher can help him towards knowledge, leading him step by step from principles he already knows to conclusions hitherto unknown to him. Nor would this external aid be necessary if the human mind were always strong enough to deduce conclusions from the principles it possesses by nature; and indeed the power so to deduce is present in men, but in varying degrees.

417b 18-418a 25

SENSITIVITY

ACTUALISATIONS OF SENSE AND INTELLECT COMPARED

             THE first change in the sensitive being is caused by the parent. When it is born it is already endowed as with knowledge. Actual sensation corresponds to the act of thinking. § 373-4

             They differ, however. For the actuation of sense-operations is from without; namely from the visible, the audible, and so on for the other senses. The cause [of the difference] is that sensation, even in act, is of particulars: whereas scientific knowledge is of universals. For the latter are, in a way, within the soul itself; hence the act of the intellect is interior and at will; whereas sensation is not from within the soul, and requires that a sense-object be presented. The same holds good of the sciences which concern sense-objects, and for the same reason, i.e. that sense objects are singulars and are external. But there will be time later to deal with these more conclusively.§§ 375-80

             For the present it is sufficiently established that 'in potency' is not univocally predicated; but it means one thing when, for example, we say that a child is able to be a soldier, and quite another thing when we say this of an adult. The same holds of the sensitive power. Since, however, this distinction has no name, and yet it is settled that the [two stages] differ, and in what way, it is necessary to use the expressions 'to be acted upon' and 'to be altered' as if they were precise terms. The sensitive power is potentially that which the sense-object is actually, as we have said. It is acted upon in so far as it is not like: it becomes like, in being acted upon; and is then such as is the other.§§ 381-2