ARTICLE ARISTOTLE ON EIDEI DIAPHERONTOI* Robert L. Gallagher 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 eıˆdos 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.’ KEYWORDS: Aristotle; metaphysics; slavery; form; genos; species; individual; particular Aristotle says that Socrates and Callias differ in form (eıˆdos) from other people (Met. 981a5f) and that a city-state must be composed of people who differ in eıˆdos (Pol.1261a23). He also says that some people have souls of one sort, and others have souls of another sort (Pol.1254b33–4). That comment also suggests that people differ in eıˆdos, for if ‘the soul is substance as form (eıˆdos) of a natural body’ (An. 12a19–20), and people have different types of soul, then, their form, i.e. their primary substance, would differ. There we have three passages in which Aristotle, disturbingly, says that human beings differ in eıˆdos. We find that disturbing, because it conflicts with our understanding of the nature of soul as form in Aristotle’s metaphysical works. As Code writes: primary substance ... is general in the sense that it is the same for each member of the species. The very same set of capacities (namely, human soul) in virtue of which my body constitutes me, also is that in virtue of which your body constitutes you. The primary source of our being, of our being what we essentially are, is the same for each of us. 1 *I thank the National Endowment for the Humanities for supporting my work on this paper through my participation in an NEH summer seminar at the University of Colorado in 2004. I also thank Christopher Shields, who led the seminar, and who supported me in taking the approach of this paper, and Alan Code who first introduced me to being and form in Aristotle’s Metaphysics. 1 A. Code, ‘The Aporematic Approach to Primary Being in Metaphysics Z’, Canadian Journal of Philosophy, 10 (1984): 41–65. British Journal for the History of Philosophy 19(3) 2011: 363–384 British Journal for the History of Philosophy ISSN 0960-8788 print/ISSN 1469-3526 online ª 2011 BSHP http://www.informaworld.com DOI: 10.1080/09608788.2011.563517