De Rervm Natvra Constantivm Scientia, Principiis Et Affectionibvs Commvnibvs, Dispvtatio

XIX. The word motion is taken broadly for every change that is in some way sensible, whether it consists of successive parts or not, yet excluding generation, which, even if it is a certain change, nevertheless is not of that in which it exists (as is said in the definition of nature)—that is, the composite. The meaning of these words is this: the composite exists prior by nature before the motion exists, of which nature is the principle. With this posited, since the composite cannot be the cause—either efficient or material—of generation, it follows that the principle of generation is not nature. Even though the composite is sometimes called the subject of generation, this must be taken according to reason, insofar as generation is predicated of the composite as an accident is of a subject.

XX. The final words of the definition, in which it exists primarily of itself, and not according to accident, there is no doubt that they can be understood concerning the parts that are in a natural thing and compose it—not only separately but also conjointly, that is, concerning the whole quiddity essence. Since although conjointly they are the same as the composite, and the same cannot inhere in itself in reality, yet we often say that "nature" is what is in a natural thing, and we often say that what is in a thing is the same as the thing to which it is attributed; e.g., we attribute goodness, wisdom, and equality to GOD, which are distinguished from GOD not in reality but only by reason.

XXI. But if we wish to render the sense of the same words from the intent of Aristotle, they must be taken for the parts separately only, that is, for both matter and form. For the Philosopher himself testifies to this in the second book of the Physics, texts 4, 10, and 12, in not entirely obscure words. From this (if matter contributes to motion only by suffering receiving) it follows that nature is not an active only, but also a passive principle of motion. That this may be made more clear, it must be noted that matter contributes to receiving motion in two ways: either according to the natural inclination of the thing itself, or not according to its inclination. Only that is nature which it receives according to the inclination of the thing, until motion is received according to the inclination of the thing, the power and potentiality of which receiving the natural thing has in the order of natural things; so that it is not repugnant to any natural virtue of its own that might strive against it; an example of this is in a heavy thing, when it is carried aloft against its nature.