Mechanistic theories of natural kinds develop out of Boyd’s homeostatic property cluster (HPC) view. The HPC view is a theory of natural kinds designed to work in domains with high individual variability. The HPC view is offered as a third way between essentialism and nominalism about kinds in the special sciences (Boyd 1991, 1997, 1999; Kornblith 1993; Wilson 1999, 2005; see also the entry on natural kinds).