By defending the following views – that Aristotle identifies the generator and perhaps the obstacle remover as an essential cause of the natural sublunary elemental motion in Physics VIII 4; that this view is consistent with the view of Physics II 1 that the sublunary simple bodies have a principle of internal motion; and that the sublunary and the celestial elements have a nature in the very same way – I shall offer what has so far eluded Aristotelian commentators: a (...) consistent interpretation of Aristotle's theory of the natural motions of the sublunary and also the celestial elements. (shrink)

Aristotle’s principle that “nature does nothing in vain” (NDNIV) is central to his teleological approach to understanding organisms. First, we argue that James G. Lennox’s influential account of NDNIV is unsuccessful. Second, we propose an alternative account that includes a natural state model. According to a natural state model of development, an organism will develop toward its natural state unless interfering forces prevent that from happening. Third, we argue that this account also fits Aristotle’s discussion in the Generation of Animals (...) and can explain monstrosities in nature that at first sight seem to be counterexamples to NDNIV. Fourth, we take a broader look at NDNIV, arguing that it does not entail that all structures are teleological (since it accommodates the thought that by-products and some neglected items that Aristotle calls “tokens” are nonteleological), that it does not entail that there is only one function per organ, that NDNIV is not an anthropocentric principle, and that, perhaps surprisingly, the teleological structures of an organism can benefit others apart from the organism and its progeny. Finally, we argue that Aristotle endorsed an empirical justification of NDNIV wherein the principle is justified by its many successful applications. (shrink)