 There has, however, been a move in general philosophy of science that, if acceptable, would transform the relationship between the taxonomic and explanatory features of species. This move was influentially initiated by Richard Boyd (1999a). It begins with the claim that the attempt to define natural kinds in terms of spatiotemporally unrestricted, intrinsic, necessary and sufficient conditions is a hangover from empiricism that should be abandoned by realist metaphysics. Instead, natural kinds should be understood as kinds that support induction and explanation, where generalisations at work in such processes need not be exceptionless. Thus understood, essences of natural kinds, i.e., their “natures”, need be neither intrinsic nor be possessed by all and only members of the kinds. Instead, essences consist of property clusters integrated by stabilising mechanisms (“homeostatic property clusters”, HPCs). These are networks of causal relations such that the presence of certain properties tends to generate or uphold others and the workings of underlying mechanisms contribute to the same effect. Boyd names storms, galaxies and capitalism as plausible examples (Boyd 1999b: 82ff.). However, he takes species to be the paradigmatic HPC kinds. According to this view, the genealogical character of a species’ nature does not undermine its causal role. Rather, it helps to explain the specific way in which the properties cohere that make up the taxon’s essence. Moreover, these can include extrinsic properties, for example, properties of constructed niches (Boyd 1991: 142, 1999a: 164ff.; Griffiths 1999: 219ff.; R. Wilson et al. 2007: 202ff.).