Physiological Introduction or Principles of the Human Body

since it consists of this as a constitutive, or component, part. The third reason is: to be an intrinsic and essential material principle is to be an essential part according to the first supposition, upon the removal of which the quidditative concept of the thing perishes. Therefore, Aristotelian primary matter is one essential part of the human body, and indeed that part by virtue of which it agrees with every other natural body.

They say 2. That there is a substantial form, or formal principle, which in the human body is the rational soul: and it is the other, and indeed its most principal, essential part. Thus hold all who believe in God. The first reason is: because there is a determinative primary act of a substantial composite, but such an act is a substantial form; therefore, etc. They prove the minor premise: primary matter in a substantial composite is not such an act, since it is indifferent and only a passive potency, and thus receptive of forms. Therefore, only the substantial form is the primary act of a substantial composite—that is, it is that first thing which actuates, or determines, the primary matter toward a certain species, for example, to compose a human rather than a donkey. Furthermore, because there exists

primary matter according to the first conclusion; therefore, there also exists a substantial form, for without this, that at least cannot exist naturally, and according to some, not even supernaturally. Furthermore, it is clearer than light that a donkey, for example, as a donkey, is a substance and not an accident; therefore, that by which a donkey is formally a donkey is not an accident. They subsume: but that by which a donkey is distinguished from every other composite is that by which a donkey is formally a donkey; therefore, that by which a donkey is distinguished from every other is a substance. And again they subsume: but that by which a donkey is distinguished from every other is a form; therefore, that form is substantial. Hence it is established that a substantial form exists. Furthermore, because every composite has its primary act, which is the substantial form, as we heard a little before, but the human body is a substantial composite; therefore, it must have its primary act, or substantial form. They subsume: but a living human body is a living substantial composite; therefore, it must have a living substantial form, or substantial life, which is