 Such purely explanatory accounts are descendants of the second use of “human nature” in the traditional package, the difference being that they don’t usually presuppose some notion of the fully developed human form. However, where some such presupposition is made, there are stronger grounds for talking of an “essentialist” account. Elliott Sober has argued that the key to essentialism is not classification in terms of necessary and sufficient conditions, but the postulation of some “privileged state”, to the realisation of which specimens of a species tend, as long as no extrinsic factors “interfere” (Sober 1980: 358ff.). Such a dispositional-teleological conception, dissociated from classificatory ambitions, would be a fourth form of essentialism. Sober rightly associates such an account with Aristotle, citing Aristotle’s claims in his zoological writings that interfering forces are responsible for deviations, i.e., morphological differences, both within and between species. A contemporary account of human nature with this structure will be discussed in  section 4.