 The much-discussed claim that species are individuals (Ghiselin 1974; Hull 1976, 1978), which developed as part of a response to the perceived failure of essentialism about species (Barker 2013, Sober 1980), might be viewed in this same light. The species-as-individuals thesis reflects the way in which species were treated within systematics and evolutionary biology not as kinds but instead as spatiotemporally restricted lineages, with individual organisms as their physical parts (Ereshefsky 1992; R.A. Wilson 1999b). The species-as-individuals thesis was originally presented and seen as making a radical break with previous views of the ontological status of species, as it implied that biologists and philosophers alike had misidentified the basic ontological category to which species belonged. But over time, both as its proponents have clarified what the thesis implied (e.g., gravitating to talk of historical entities rather than individuals) and as more sophisticated options for defenders of the view that species are kinds were developed (e.g., Boyd 1999, Griffiths 1999, R.A. Wilson 1999a), this radical edge to the thesis has diminished. A now widely accepted insight clarified in the process is that in the case of many species, organisms belong to them (as parts or members) by virtue of their interactions and their extrinsic rather than intrinsic properties (Barker 2010; cf. Devitt 2008). Whether this combats (or instead exemplifies) what the historian James Elwick has recently called “resilient essentialisms” (Elwick 2017; cf. Hull 1965) remains contentious. 