two ways (if we exclude the sense in which 'from' means 'after' as we say 'from the Isthmian games come the Olympian'), (a) as the man comes from the boy, by the boy's changing, or (b) as air comes from water. By 'as the man comes from the boy' we mean 'as that which has come to be from that which is coming to be, or as that which is finished from that which is being achieved' (for as becoming is between being and not being, so that which is becoming is always between that which is and that which is not; and the learner is a man of science in the making, and this is what is meant when we say that from a learner a man of science is being made); on the other hand, coming from another thing as water comes from air implies the destruction of the other thing. This is why changes of the former kind are not reversible,—the boy does not come from the man (for that which comes to be does not come to be from the process of coming to be, but exists after the process of coming to be; for it is thus that the day comes from the morning—in the sense that it comes after the morning; and therefore the morning cannot come from the day); but changes of the other kind are reversible. But in both cases it is impossible that the number of terms should be infinite. For terms of the former kind being intermediates must have an end, and terms of the latter kind change into one another; for the destruction of either is the generation of the other.
At the same time it is impossible that the first cause, being eternal, should be destroyed; for while the process of becoming is not infinite in the upward direction, a first cause by whose destruction something came to be could not be eternal.
- 994b1 The meaning seems to be, that in this kind of change the y that comes from x is not simply x rearranged, but x affected by a lapse of time. ∴ x cannot be got from y.
- Cf. a27-29.
- This paragraph is very obscure. Aristotle has in a11-19 given a general argument which applies to all the four causes, to show that there must always be a first cause. This, he assumes, must be eternal. He now applies this argument to the prime material cause, and shows that it must be indestructible. There are two difficulties in the paragraph:—
(1) It seems pointless to say that the first cause must be indestructible because it is eternal. Ground and consequent appear to be identical. But probably the object is to show that the first cause must be to its