 Distinguishing causation from ontology does not imply that causal relations are ontologically irrelevant. Having causal effects may be a criterion for an entity to be real (Gellner 1956, Bhaskar 1975, Elder-Vass 2010). Causal structure is also often regarded as central to the nature of various entities. Several theorists argue that kinds are individuated by their causal roles (Fodor 1974, Khalidi forthcoming). Some theorists of biological and artifactual kinds regard patterns of reproduction to be part of what individuates these kinds. And some theorists of human kinds regard certain causal feedback loops to be characteristic of human kinds (see  section 4.3.3).  The burden of such accounts is to distinguish the causal factors that are part of an account of ontology from those that are “merely” causally connected.