Aristotle holds that there must be multiple forms of human being and those forms constitute a genos, this paper argues. Aristotle advances his claim by arguing that the strength of a polis rests on the existence of a spectrum of useful essential differences among its citizens. The paper rejects the notion that eîdos is a homonym, and argues that it signifies `form,' not `species.' Its theses are based on analysis of passages in the Ethics, Metaphysics, Politics and other works. The (...) argument of the paper is compatible with `individual' or `particular' forms. The paper also proposes a solution to the issue of `natural slavery.'. (shrink)