On the Secrets of Women

always conserve animals in specific being? And it is said, no, because if so, then the species would be generable, which is false. The falsity is clear, because the species is perpetual. I say, when this or that individual is generated, then specific nature is generated under this designated being, and according to a part, although it is not generated according to its whole extent. Whence note that nature operates secretly in universals, as Gilbertus Porretanus Gilbert of Poitiers says in his "Six Principles," in chapter 1, on the chapter concerning form. And because it intends to produce masculine nature, namely man in general, or a horse, and yet it produces a particular one, such as Socrates in the text: Sortem, this happens because it finds certain matter, and designated in this determined place. And therefore, if it found the whole nature at once, it would produce every man at once. But because it finds one portion of the menstrual flow of this or that woman, it therefore produces this or that particular man.

The cause, however, why these animals—and especially humans—do not endure according to the same nature, matter, and number is stated in the second book of On Generation and Corruption. Their bodily substance does not endure, but is corruptible; it could not reiterate the same thing in number, but the substance of man, accepted according to the principles of the individual, is corruptible. Therefore, the generation of man is cast off; wherefore the generation of humans will not be eternal according to number; nevertheless, however, the generation...