Metaphysics

Our inquiry is about substance; for the principles and causes of substances are what is sought. For if the universe is a kind of whole, substance is its first part; and if they are in succession, even so substance is first, then quality, then quantity. But at the same time these other things are not even, so to speak, beings in an unconditional sense, but are qualities and movements, or else even the ‘not-white’ and the ‘not-straight’; at any rate we say that these also are, as when we say ‘there is a not-white’. Further, none of the other things can exist apart. And the ancients also bear witness to this in fact; for they sought the principles, elements, and causes of substance. Now the moderns tend to posit universals as substance (for genera are universals, which they say are principles and substances rather because they inquire dialectically); but the ancients posited particular things, like fire and earth, but not the common thing, body. And there are three substances: one is sensible—of which one part is eternal and another destructible, which all admit, like plants and animals—of which we must grasp the elements, whether one or many; another is unmoved, and this some say exists apart, some dividing it into two, others putting the Ideas and the mathematical objects into one nature, and others admitting only the mathematical objects among these. The former substances, then, belong to physics (for they involve movement), but the latter to another science, if they have no principle in common. Sensible substance is changeable. And if change is from opposites or from intermediates, and not from all opposites (for voice is ‘not-white’) but from the contrary, there must be something underlying which changes into the contrariety; for the contraries themselves do not change.

​Further, the one persists, but the contrary does not persist; therefore, there is a third thing besides the contraries, namely matter. If, then, changes are four in number, either in respect of ‘what’ or of ‘of what quality’ or ‘how much’ or ‘where’, and simple generation and destruction are in respect of ‘this’, and increase and decrease are in respect of quantity, and alteration is in respect of affection, and motion is in respect of place, then the changes must be into the corresponding contrarieties. It is necessary, then, that the matter should change, having the potentiality for both; and since ‘being’ is double, everything changes from that which is potentially to that which is actually (for instance, from potentially white to actually white, and similarly in the case of increase and decrease), so that not only is it possible for something to come to be accidentally from non-being, but also all things come to be from being, but from being potentially, and from non-being actually. And this is Anaxagoras’ ‘one’; for this is better than ‘all things together’—and Empedocles’ mixture, and Anaximander’s, and as Democritus says: ‘all things were together potentially, but not actually’; so that they would have laid hold of matter. And all things that change have matter, but different matter; and of the eternal things, those which are not generable but are movable in space have matter, yet not matter for generation, but for motion from one place to another. One might raise the question, from what kind of non-being generation takes place; for non-being has three senses. If, then, something is potentially, yet it does not come from anything whatsoever, but different things come from different things; nor is it sufficient that ‘all things were together’ ; for they differ in their matter, since otherwise why did they become infinitely many and not one? For Mind is one, so that if matter also were one, that would have been produced in actuality which the matter was potentially. There are, then, three causes and three principles: two being the contrariety, of which one is the formula or form and the other the privation, and the third being the matter.