Genus and Species

Thomas has been explainining how the essence of a composite being can include both matter and form. Before we move along to the sixth paragraph of Chapter 2, I’d like to spend some time with the last sentence of paragraph 5:

If animal were not all that man is but rather only a part of him, then animal would not be predicated of man, for no integral part is predicated of its whole.

Because a genus is less specific than a species, I tend to think of it as less extensive than a species. For example, when I hear that “Man is a rational animal” I mentally take some notion of animal and add rationality to it. Aquinas’ point, here, is that “animal” is wider, more extensive, than “man” is–it includes all of the attributes of all animals, including men. What defines a species isn’t something added to the definition of animals; it’s what distinguishes this kind of animal from that kind.

I’m going to have to keep an eye on this mistake, and see if it’s been leading me astray.

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