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

XXXIV. It could be that such a definition of appetite is assigned, by which artificial forms would be explained as being "desired" by matter—if, indeed, it were defined as the potentiality by which matter is referred to a future form due to it as a passive principle. However, because by the received use of speech we are accustomed to deny that forms produced by miracle—such as health, sight, and others of the same kind—are desired by matter (which nevertheless are due to matter as a passive principle), for that reason we consider the former definition more convenient.

XXXV. From the definition of matter, last of all, it follows that matter is a substance, since it is a part of a substance or of a subject subsisting of itself. And it is a corporeal substance, because it assumes quantity to itself as due to it by its own nature. Whether it be a perfect body or not, and whether it obtains a perpetual quantity joined to itself, we shall say in the next following chapter. Wherefore, let these things concerning matter be sufficient.

CHAPTER IV.

ON FORM.

XXXVI. At almost the same beginning as thought began to be given to matter, philosophers were induced to think about form. For when they observed that every thing which is produced is produced in another, they gathered that the produced thing depends on that in which it is produced, is ordered so that it might perfect it, and finally does not have the power of subsisting of itself. They then named this "form," which, with a definition consistent with the principles by which it was discovered, can be defined as: a perfection, having an order placed in it by its own nature to another in which it is made, as in something subsisting of itself, which it perfects by existing within it. That is, that which by its own nature is referred to another, so that by the conjunction of itself with that, it may be the perfection of that and not of another.

XXXVII. There are two genera of forms: one of an accident, another of a substance. The way by which we are led to investigate this double genus is manifold, but this our opinion is the most certain of all: there are two modes by which this double genus of forms could be denied...