 This approach assumes that the conceptual distinction between nomological and metaphysical necessity corresponds to a substantial one, such that fundamental causal laws are metaphysically contingent and what supervenes of metaphysical necessity on the fundamental physical domain is necessarily physical. Both these assumptions have been challenged. Moral anti-naturalists such as G.E. Moore maintain that fundamental moral features supervene of metaphysical necessity on natural features, and on neo-Aristotelian essentialist ontologies, strongly emergent features, were they to exist, would supervene with metaphysical necessity on physical features. See, however, Howell (2009) and Noordhof (2010) for strategies aimed at defending supervenience-based approaches to strong emergence.