Marsilio Ficino’s Platonic Theology, Volume II

10We think they fell into this error because they observed that some branches of knowledge concern composite things. Such is knowledge of a human being, who is composed of animal and rational as genus and difference; such too is knowledge of seven, ten, and other numbers gathered from numbers or units. We, however, hold that a human being, precisely as human, is one and simple, because his form is one. A sign of this is that he is not divided into several human beings. If you divide him according to species into genus and difference, neither constituent is a human being. If you divide him into individual parts—head, breast, and thigh—none of them is a human being. You do cut the body, because you tear it into members that are bodies; you do not cut the human being, because you do not cut him into human beings. Whatever is such a thing in itself and is not divided into several things of the same kind is certainly, insofar as it is such, indivisible and simple. Ten too, insofar as it is ten, is not divided. It is only one species and one form, which we cannot partition into several tens. If we divide it, we divide a number because we divide it into numbers; we do not divide ten because we do not distribute it into tens. Nor is it an objection that genus and difference appear to be included within a species. There are not two forms within it, but one. Although in the order of things being animal is one thing and being rational another, in a human being they are the same; and, to speak in Platonic terms, human nature itself is a certain rationality. Rationality in a human being is nothing other than animality itself brought into the act of reason. The species, then, is such a simple form, the foundation of simple being: it does not distribute itself among individual human beings, but communicates itself wholly to each, and through it the individuals are one.