There is an interesting history to modern science’s views about the kinds of things that can produce physical effects (Papineau 2001). It will be worth rehearsing this history in outline, if only to forestall a common reaction to ontological naturalism. It is sometimes suggested that ontological naturalism rests, not on principled grounds, but on some kind of unargued commitment, some ultimate decision to nail one’s philosophical colours to the naturalist mast.[4] And this diagnosis seems to be supported by the historical contingency of ontologically naturalist doctrines, and in particular by the fact that they have become widely popular only in the past few decades. However, familiarity with the relevant scientific history casts the matter in a different light. It turns out that naturalist doctrines, far from varying with ephemeral fashion, are closely responsive to received scientific opinion about the range of causes that can have physical effects.