LESSON 9

The Substantial Priority of Actuality in Incorruptible Things

Chapter 8: 1050b 6-1051a 3

             792. But actuality is prior to potency in a more fundamental sense; for eternal things are prior in substance to corruptible ones, and nothing eternal is potential.

             793. The reason of this is that every potency is at the same time a potency for opposite determinations. For what is incapable of existing does not exist in any way; and it is possible for everything that is capable of existing not to exist actually. Therefore whatever is capable of existing may either be or not be, and thus the same thing is capable both of being and of not being. But what is capable of not being may possibly not be; and what may possibly not be is corruptible: either absolutely, or in the sense in which it is said to be possible for it not to be, either according to place or to quantity or to quality. And the term absolutely means in reference to substance.

             794. Therefore nothing that is incorruptible in an absolute sense is potential in an absolute sense. But there is nothing that hinders it from being so in other respects, for example, in reference to quality or to place. Therefore all incorruptible things are actual.

             795. And none of those things which exist necessarily are potential. In fact such things are the first; for if they did not exist, nothing would exist.

             796. Nor is eternal motion potential, if there be such a thing; and if anything is moved eternally, it is not moved potentially except in reference to whence and whither. And nothing prevents the matter of this sort of thing from existing.

             797. And for this reason the sun and the stars and the entire heaven are always active, and there is no need to fear, as the natural philosophers do, that they may at some time stand still. Nor do they tire in their activity; for in them there is no potency for opposite determinations, as there is in corruptible things, so that the continuity of their motion should be tiresome. For the cause of this is that their substance is matter and potency and not actuality.

             798. Moreover, incorruptible things are imitated by those which are in a state of change, such as fire and earth; for these latter things are always active, since they have motion in themselves and of themselves.

             799. But all other potencies which have been defined are potencies for opposite determinations; for what is capable of moving something else in this way is also capable of not moving it in this way, i.e., all those things which act by reason. And irrational potencies will also be potencies for opposite determinations by being absent or not.

             800. If, then, there are any natures or substances such as those thinkers who in their theories proclaim the Ideas to be, there will be something much more scientific than science itself, and something much more mobile than motion itself; for the former will rather be the actualities and the latter the potencies of these. Hence it is evident that actuality is prior to potency and to every principle of change.

COMMENTARY

             1867. Aristotle proved above that actuality is prior to potency in substance, definition and perfection, by arguments drawn from corruptible things themselves; but here he proves the same point by comparing eternal things with corruptible ones.

             This part is divided into two members. In the first (792:C 1867) he proves his thesis; and in the second (800:C 1882), by the thesis thus proved, he rejects a certain statement made by Plato ("If, then").

             In regard to the first he does two things. First, he proves his thesis. This he does by the following argument: eternal things are compared to corruptible ones as actuality to potency; for eternal things as such are not in potency, whereas corruptible things as such are in potency. But eternal things are prior to corruptible ones in substance and perfection; for this is evident (784:C 1856). Hence actuality is prior to potency both in substance and perfection. He says that his thesis is proved in a more proper way by this argument, because actuality and potency are not considered in the same subject but in different ones, and this makes the proof more evident.

             1868. The reason (793).

             Second, he proves one assumption which he made, namely, that nothing eternal is in potency; and in regard to this he does two things. First, he gives an argument to prove this, and it runs as follows: every potency is at one and the same time a potency for opposite determinations. Now he does not say this about active potency, for it has already been shown (747:C 1789) that irrational potencies are not potencies for opposite determinations; but he is speaking here of passive potency, on the basis of which a thing is said to be capable of being and not being either absolutely or in a qualified sense.

             1869. Now the claim which he made he proves by an argument to the contrary; because where such potency does not exist, neither of the opposite determinations is possible; for what is incapable of being never exists in any way. For if a thing is incapable of being, it is impossible for it to be, and it is necessary for it not to be. But what is capable of being may possibly not be actual. Hence it is evident that what is capable of being may either be or not be; and thus the potency is at one and the same time a potency for opposite determinations, because the same thing is in potency both to being and non-being.

             1870. But what is capable of not being may possibly not be, for these two statements are equivalent ones. Moreover, what may possibly not be is corruptible either absolutely or in a qualified sense inasmuch as it is said to be possible for it not to be. For example, if it is possible for some body not to be in place, that body is corruptible as far as place is concerned; and the same applies to quantity and quality. But that is corruptible in an absolute sense which is capable of not existing substantially. Therefore it follows that everything potential inasmuch as it is potential is corruptible.

             1871. Therefore nothing (794).

             Second, he draws from the foregoing the conclusion at which he aims; and in regard to this he does three things. First, he concludes to this thesis about eternal things, inferring from the observations made above that, if everything potential is corruptible, it follows that nothing which is incorruptible in an absolute sense is a potential being, provided that we understand incorruptible things in an absolute sense and potential being in an absolute sense in reference to substance.

             1872. But nothing prevents something that is incorruptible in an absolute sense from being potential in a qualified sense, in reference either to quality or to place. For example, the moon is in a state of potency to being illuminated by the sun; and when the sun is in the east it is in a state of potency with regard to being in the west. It is evident from what has been said, then, that all eternal things as such are actual.

             1873. And none (795).

             Second, he comes to the same conclusion about necessary things as he did about eternal things, because even in corruptible things there are certain necessary aspects; for example, man is an animal, and every whole is greater than its part. Hence he says that nothing necessary is potential; for necessary things are always actual and incapable of being or not being. And those things which are necessary are the first of all things, because if they ceased to exist, none of the others would exist; for example, if essential predicates, which are referred to a subject necessarily, were taken away, accidental predicates, which can be present and not present in some subject, could not be present in any subject. It follows, then, that actuality is prior to potency.

             1874. Nor is (796).

             Third, he comes to the same conclusion about eternal motion as he did about eternal substances; and in regard to this he does three things. First, from what has been said above he concludes to his thesis. He says that, if some motion is eternal, that motion is not potential; nor is anything that is moved eternally in a state of potency to motion, but it is in a state of potency to this or to that place, i.e., inasmuch as it goes from this place to that place. For since motion is the actuality of something in potency, everything which is being moved must be in potency to the goal of that motion, not however as regards motion itself, but as regards some place to which it tends by its motion.

             1875. And since what is being moved must have matter, he adds that nothing prevents a thing which is being moved by an eternal motion from having matter; because, even though it is not in potency to motion in an absolute sense, it is nevertheless in potency to this or to that place.

             1876. And for this (797).

             Second, he draws a corollary from the above discussion. For since what is being moved by an eternal motion is not in potency to motion itself (and the motion of the heavens is eternal according to the discussion in Book VIII of the Physics , it follows that the sun and the moon and the stars and the entire heaven are always active, because they are always being moved and are acting by means of their motion.

             1877. Nor is it to be feared that at some time the motion of the heavens may cease, as "some of the natural philosophers feared it would," namely, Empedocles and his followers, who held that at times the world is destroyed by discord and is restored again by friendship. Hence he says that this is not to be feared, because they are not potentially immobile.

             1878. And for this reason too incorruptible things insofar as they are being moved do not tire in their activity, because "the potency for opposite determinations" is not found in them, namely, the ability to be both moved and not moved, as is found in corruptible things, which have these as a result of motion. And thus in this way continuous motion becomes laborious for them. For corruptible things labor insofar as they are moved; and the reason is that they are in a state of potency both for being moved and not being moved, and it is not proper to them by reason of their substantial nature always to be undergoing motion. Hence we see that the more laborious any motion is, the nearer also does the nature of the thing come to immobility; for example, in the case of animals it is evident that motion in an upward direction is more laborious.

             1879. Now what he says here about the continuity of celestial motion is in keeping with the nature of a celestial body, which we know by experience. But this is not prejudicial to the divine will, on which the motion and being of the heavens depend.

             1880. Moreover, incorruptible things (798).

             Third, he compares corruptible bodies with incorruptible ones from the viewpoint of activity. First, he does this insofar as they are alike. He says that the bodies of those things whose being involves change resemble incorruptible bodies insofar as they are always acting; for example, fire, which of itself always produces heat, and earth, which of itself always produces proper and natural activities. And this is true because they have motion and their own proper activity of themselves--inasmuch, namely, as their forms are principles of such motions and activities.

             1881. But all the other (799).

             Second, he compares them insofar as they are unlike. He says that in contrast with eternal things, which are always actual, the other potencies of mobile things, about which the truth has been established above, are all potencies for opposite determinations. But this is verified in a different way; for rational potencies are potencies capable of opposite determinations because they can move in this way or not, as has been said above (747:C 1789); whereas irrational potencies, though acting in one way, are themselves also potencies of opposite determinations in view of the fact that they can be present in a subject or not; for example, an animal can lose its power of vision.

             1882. If, then (800).

             As a result of what has been said he rejects a doctrine of Plato. For Plato claimed that there are certain separate Forms, which he held to have being in the highest degree; say, a separate science, which he called science-in-itself; and he said that this is foremost in the class of knowable entities. And similarly he maintained that motion-in-itself is foremost in the class of mobile things. But according to the points made clear above, something else besides science-in-itself will be first in the class of knowable things; for it was shown that actuality is prior to potency in perfection, and science itself is a kind of potency. Hence speculation, which is the activity of science, will be more perfect than science is; and the same will apply in the case of other things of this kind. Lastly he summarizes his discussion, saying that actuality is prior to potency and to every principle of motion.