  Whatever their motivation, ontological naturalists are by definition (on this second reading of the doctrine) agreed that platonism is false. Sometimes ontological naturalism is motivated by metaphysical doctrines, for instance by the principle that everything that exists has causal powers. Subscribers to this principle include Armstrong (1997) who calls it the Eleatic Principle; for criticism, see Colyvan (2001 ch. 3) and Papineau (2009).