LESSON 1

The Division of Potency into Active and Passive.

The Nature of Incapacity and Privation

  Chapter 1: 1045b 27-1046a 35

             742. We have dealt then with the primary kind of being and the one to which all the other categories of being are referred, namely, substance. For it is in reference to the concept of substance that the other categories are called beings, i.e., quantity, quality, and others which are spoken of in this way; for all involve the concept of substance, as we have stated in our first discussions (562). And since being is used in one sense of quiddity or quantity or quality, and in another sense of potency and actuality and activity, let us now establish the truth about potency and actuality. And first let us consider potency in the most proper sense of the term, although not the one most useful for our present purpose; for potency and actuality are found in more things than those which are referred merely to motion. But when we have spoken about this sense of potency we shall, in our discussions about actuality, also explain the other senses of potency.

             743. That the terms potency and can are used in many senses we have made evident elsewhere (467). And all of those senses of potency which are equivocal may be dismissed; for some senses of potency [or power] are merely figurative, as in geometry. And we say that things are possible or impossible because they either are or are not in some particular way. But all those potencies belonging to the same species are principles and are referred to one primary kind of potency, which is the principle of change in some other thing inasmuch as it is other. For one kind is a potency for being acted upon, which is in the patient and is the principle of its being passively moved by another inasmuch as it is other; and another kind of potency is the state of insusceptibility to change for the worse and to corruption by some other thing inasmuch as it is other, i.e., by a principle of change. And the intelligible character of the primary kind of potency is found in all of these terms. Again, these potencies are said to be potencies either just for acting or for being acted upon, or for acting or being acted upon well, so that in these latter kinds of potencies the notes of the prior kind are somehow present.

             744. It is evident, then, that in one sense the potency for acting and for being acted upon are one; for a thing is potential both because it itself has the potency for being acted upon, and because something else can be acted upon by it. And in another sense these potencies are different; for the one is in the patient, since it is because it has a principle, and because matter is a principle, that the patient is acted upon and changed by something else. For what is oily is capable of being burnt, and what is yielding in some way is capable of being broken (and the supposit is capable of being expressed); and the same is true in other cases. And another kind of potency is in the agent, as the potency to heat and the potency to build--the former in the thing capable of heating, and the latter in the person capable of building. Hence, inasmuch as a thing is by nature a unity, it cannot be acted upon by itself; for it is one thing and not also something else.

             745. And incapacity or impossibility is the privation contrary to such potency, so that every potency and incapacity belong to the same subject and refer to the same attribute. And there are various kinds of privation; for there is one kind of privation when a thing does not have some attribute which it is naturally disposed to have, either in general, or when it is naturally disposed to have it. And this is so either in a particular way, for example, completely, or even in any way at all. And in some cases if things are naturally disposed to have some attribute and do not have it as a result of force, we say that they are deprived of it.

COMMENTARY

             1768. Having established the truth about being as divided into the ten categories, the Philosopher's aim here is to establish the truth about being as divided into potency and actuality. This is divided into two parts. In the first (742:C 1768) he links up this discussion with the foregoing one, and explains what he intends to do in this book. In the second (743:C 1773) he carries out his announced plan ("That the terms").

             He accordingly points out, first (742), that he has already discussed above the primary kind of being to which all the other categories of being are referred, namely, substance. And he explains that all the other categories are referred to substance as the primary kind of being, because all other beings--quantity, quality, and the like--involve the concept of substance. For being is said of quantity because it is the measure of substance; and of quality because it is a certain disposition of substance; and the same thing applies in the case of the other categories. This is evident from the fact that all accidents involve the concept of substance, since in the definition of any accident it is necessary to include its proper subject; for example, in the definition of snub it is necessary to include nose. This was made clear at the beginning of Book VII (586:C 1347).

             1769. But being is variously divided. One division is based on its designation as whatness (i.e., substance), quantity or quality, which is its division into the ten categories. Another is its division into potency and actuality or activity, from which the word actuality [or act] is derived, as is explained later on (758:C 1805). And for this reason it is now necessary to deal with potency and actuality.

             1770. It is first necessary to speak of potency in its most proper sense, although not the one which is most useful for our present purpose. For potency and actuality are referred in most cases to things in motion, because motion is the actuality of a being in potency. But the principal aim of this branch of science is to consider potency and actuality, not insofar as they are found in mobile beings, but insofar as they accompany being in general. Hence potency and actuality are also found in immobile beings, for example, in intellectual ones.

             1771. And when we shall have spoken about the potency found in mobile things, and about its corresponding actuality, we will also be able to explain potency and actuality insofar as they are found in the intelligible things classed as separate substances, which are treated later on (792:C 1867). This order is a fitting one, since sensible things, which are in motion, are more evident to us, and therefore by means of them we may attain a knowledge of the substances of immobile things.

             1772. From this consideration the meaning of another text also becomes evident, which says, "And potency in the proper sense is not the only one which is useful for our present purpose;" because even though the potency which is present in mobile things is potency in its most proper sense, this is still not the only sense in which potency is used, as was explained (C 1770-71). And it is useful for our present purpose, not as though it were the principal object of our investigation, but because we may attain a knowledge of the other kinds of potency from it.

             1773. That the terms (743).

             Then he deals with potency and actuality; and this is divided into three parts. In the first (743:C 1773) he discusses potency; and in the second (768:C 1823), actuality ("Since we have dealt"); and in the third (778:C 1844), the relationship of actuality to potency ("Since we have established").

             The first is divided into two parts. In the first of these he discusses potency itself. In the second (746:C 1787) he discusses potency in relation to the things in which it is found ("And since some").

             The first is divided into two parts. In the first he deals with potency; and in the second (745:C 1784), with incapacity ("And incapacity").

             In regard to the first he does two things. First, he explains the different senses of potency. Second (744:C 1781), he makes evident a truth about potency from the things previously laid down ("It is evident").

             He accordingly says, first (743), that it has been shown elsewhere, i.e., in Book V of this work (467:C 954), that the words potency and can have a multiplicity of meanings. But in some cases this multiplicity is a multiplicity of equivocation, and in others it is a multiplicity of analogy. For some things are said to be capable or incapable because they have some principle within themselves, and this refers to those senses in which all potencies are said to be such not equivocally but analogously. But other things are not said to be capable or able because of some principle which they have within themselves; and in their case the term potency is used equivocally.

             1774. Therefore, with regard to those senses in which the term potency is used equivocally, he says that these must be dismissed for the present. For the term potency is referred to some things, not because of some principle which they have, but in a figurative sense, as is done in geometry; for the square of a line is called its power (potentia), and a line is said to be capable of becoming its square. And similarly in the case of numbers it can be said that the number three is capable of becoming the number nine, which is its square; because when the number three is multiplied by itself the number nine results, for three times three makes nine; and when a line, which is the root of a square, is multiplied by itself, a square results. And the same thing applies in the case of numbers. Hence the root of a square bears some likeness to the matter from which a thing is made; and for this reason the root is said to be capable of becoming its square as matter is capable of becoming a thing.

             1775. And similarly in the considerations of logic we say that some things are possible or impossible, not because of some potency, but because they either are or are not in some way; for those things are called possible whose opposites can be true, whereas those are called impossible whose opposites cannot be true. This difference depends on the relationship of predicate to subject, because sometimes the predicate is repugnant to the subject, as in the case of impossible things, and sometimes it is not, as in the case of possible things.

             1776. Passing over these senses of potency, then, we must consider those potencies which are reduced to one species, because each of these is a principle. And all potencies spoken of in this sense are reduced to some principle from which all the others derive their meaning; and this is an active principle, which is the source of change in some other thing inasmuch as it is other. He says this because it is possible for an active principle to be at the same time in the mobile or patient, as when something moves itself; although it is not mover and moved, or agent and patient, in the same respect. Hence the principle designated as active potency is said to be a principle of change in some other thing inasmuch as it is other; because, even though an active principle can be found in the same thing as a passive principle, this still does not happen insofar as it is the same, but insofar as it is other.

             1777. That the other potencies are reduced to this principle which is called active potency is evident; for in one sense passive potency means the principle by which one thing is moved by some other thing inasmuch as it is other. He says this because, even if the same thing might be acted upon by itself, this still does not happen insofar as it is the same, but insofar as it is other. Now this potency is reduced to a first active potency, because when anything undergoes change this is caused by an agent. And for this reason passive potency is also reduced to active potency.

             1778. In another sense potency means a certain state of insusceptibility (or impossibility) "to change for the worse," i.e., a disposition whereby a thing is such that it cannot undergo change for the worse; i.e., that it cannot undergo corruption as a result of some other thing "inasmuch as it is other," namely, by a principle of change which is an active principle.

             1779. Now it is evident that both of these senses of potency imply something within us which is referred to the undergoing of a change. For in the one sense the term designates a principle by reason of which someone cannot be acted upon; and in the other sense it designates a principle by reason of which someone can be acted upon. Hence, since the state of being acted upon depends on action, the definition "of the primary kind of potency," namely, active potency, must be given in the definition of both senses of potency. Thus these two senses of potency are reduced to the first, namely, to active potency, as to something prior.

             1780. Again, in another sense potencies are spoken of not only in relation to acting and being acted upon but in relation to what is done well in each case. For example, we say that someone is capable of walking, not because he can walk in any way at all, but because he can walk well; and in an opposite sense we say of one who limps that he cannot walk. Similarly, we say that wood is capable of being burned because it can be burned easily; but we say that green wood is incapable of being burned because it cannot be burned easily. Hence it is clear that in the definitions of those potencies which are described as potencies for acting and being acted upon well, there are included the concepts of those primary potencies which were described as potencies for acting and being acted upon without qualification; for example, to act is included in to act well, and to be acted upon is included in to be acted upon well. Hence it is obvious that all of these senses of potency are reduced to one primary sense, namely, to active potency; and therefore it is also evident that this multiplicity is not the multiplicity of equivocation but of analogy.

             1781. It is evident, then (744).

             From what has been said he now indicates something that is true about the foregoing potencies. He says that in one sense the potency for acting and that for being acted upon are one, and in another sense they are not. They are one potency if the relationship of the one to the other is considered; for one is spoken of in reference to the other. For a thing can be said to have a potency for being acted upon, either because it has of itself a potency by which it may be acted upon, or because it has a potency by which something else may be acted upon by it. And in this second sense active potency is the same as passive potency; for by reason of the fact that a thing has active potency it has a power by which something else may be acted upon by it.

             1782. However, if these two potencies--active and passive--are taken in reference to the subject in which they are found, then in this sense active and passive potency are different; for passive potency exists in a patient, since a patient is acted upon by reason of some principle existing within itself; and matter is of this sort. Now passive potency is nothing but the principle by which one thing is acted upon by another; for example, to be burned is to undergo a change, and the material principle by reason of which a thing is capable of being burned is the oily or the fat. Hence the potency itself is present as a passive principle in the thing capable of being burned. And similarly what yields to the thing touching it so that it receives an impression from it, as wax or something of this sort, is capable of doing so inasmuch as it is impressionable. "And the supposit," i.e., the male, is the proper subject of the modification resulting in an eunuch. The same is true of other things which are acted upon insofar as they have within themselves a principle for being acted upon, which is called passive potency. But active potency is in the agent, as heat in the thing which heats and the art of building in the builder.

             1783. And since active potency and passive potency are present in different things, it is obvious that nothing is acted upon by itself inasmuch as it is naturally disposed to act or to be acted upon. However, it is possible for something to be acted upon by itself accidentally, as a physician heals himself not inasmuch as he is a physician but inasmuch as he is ill. But in this case a thing is not acted upon by itself, because, properly speaking, one of the aforesaid principles is present in one and the same thing, and not the other. For the principle of being acted upon is not present in the one having the principle of action except accidentally, as has been said (744:C 1782).

             1784. And incapacity (745).

             Here he establishes the truth about incapacity, saying that incapacity (which is the contrary of the above-mentioned potency or capacity) or impossibility (which is referred to incapacity of this sort) is the privation of the potency in question. However, he says this to distinguish it from the impossible which signifies some mode of falsity, which is not referred to any incapacity, just as the possible is also not referred to any potency. For since privation and possession belong to the same subject and refer to the same attribute, potency and incapacity must belong to the same subject and refer to the same attribute. Hence there are as many senses of incapacity as there are of potency, to which it is opposed.

             1785. But it must be noted that the term privation is used in many senses. For in one sense whatever does not have some attribute can be said to be deprived of it, as when we say that a stone is deprived of sight because it does not have sight; and in another sense a thing is said to be deprived only of what it can have and does not have. And this may happen in two ways: in one way when the thing does not have it at all, as a dog is said to be deprived of sight when it does not have it; and, in another way, if it does not have it when it is naturally disposed to have it. Hence a dog is not said to be deprived of sight before the ninth day. This sense of privation is again divided. For in one sense a thing is said to be deprived of some attribute because it does not have it in a particular way, namely, completely and well; as when we say that someone who does not see well is blind. And in another sense a thing is said to be deprived of some attribute when it does not have it in any way at all; for example, we say that a person is deprived of sight who does not have sight at all. But sometimes force is included in the notion of privation, and then we say that some things are deprived of certain attributes when those which they are naturally disposed to have are removed by force.