Book 6
5
For in the case of things produced the principle of motion (either mind or art or some kind of potency) is in the producer; and in the case of things done the will is the agent—for the thing done and the thing willed are the same. Thus if every intellectual activity is either practical or productive or speculative, physics will be a speculative science; but speculative about that kind of Being which can be moved, and about formulated substance for the most part only qua inseparable from matter.
6
But we must not fail to observe how the essence and the formula exist, since without this our inquiry is ineffectual.
6
Now of things defined, i.e. of essences, some apply in the sense that snub does, and some in the sense that concave does. The difference is that snub is a combination of form with matter; because the snub is a concave nose , whereas concavity is independent of sensible matter.
7
Now if all physical terms are used in the same sense as snub—e.g. nose, eye, face, flesh, bone, and in general animal; leaf, root, bark, and in general vegetable (for not one of these has a definition without motion; the definition invariably includes matter)—it is clear how we should look for and define the essence in physical things, and why it is the province of the physicist to study even some aspects of the soul, so far as it is not independent of matter.
