The difference between generation and alteration

The difference between generation and alteration


Let us speak about generation and alteration and what they are different in; for we say that these changes are different from one another. Since, then, one thing is what is subject to something and another that property which is said (predicated) of the former, and it happens that each of them can change, we speak of alteration when the underlying thing, though perceptible and persistent, changes in virtue of its properties, whether these are contraries or intermediates. For example, a body is well and then ill, though it remains the same body; and a copper is now round and at another time with angles, but remains the same copper.

But when it changes entirely without remaining anything perceptible as a subject of the same nature, but as, for example, from seed changes entirely into blood or from water into air or from air into water entirely, then in this case we speak of generation and corruption respectively; especially if the change takes place from an imperceptible body to a perceptible body either by touch or by the whole senses, e.g. when it comes to be water or passes away into air; for air is pretty well imperceptible.

Now in such cases if any property subject to contrariety remains the same both in what has come to be and in what has passed away, as, for example, when water comes to be from air, namely, if they both are transparent or cold, the other property should not belong to that into which it changes. Otherwise it would be a case of alteration, as it is with the musical man that has passed away and become unmusical man, and yet the man remains the same. If, then, the musical and the unmusical were not properties essentially belonging to man, then it would be a case of generation and corruption respectively (that is why these are in fact qualifications of man, whereas of musical and unmusical man, generation and corruption), but now this (the musical) is in fact a property of that which remains (of man). For this reason it is a case of alteration.

So when the change from contrary to contrary is in quantity, it is increase and diminution, when in place, locomotion, when in property and qualification, alteration, but when nothing is persistent, of which that in virtue of which it changes is a property or fully accident, then it is generation and corruption. Matter most of all and strictly stands as a subject that is receptive of generation and corruption, yet in a way also matter is whatever subject to the other changes in that all subjects are receptive of contrarieties of a certain kind.

As to generation, then, whether it is or is not, and in what way it is, and alteration, let these matters be settled in this way.

 Bibliography: Aristotle On generation and corruption (319b.6 to 320a.7)
Translation: George Kotsalis