There are a number of dimensions to the realism-nominalism controversy. The topics of debate comprise: necessary connections and causality, dispositions and counterfactuals, space and time, the existence of abstract entities and mathematical objects, the existence of the theoretical entities of science. On all these except the last, Sellars takes a non-realist line: and on all these except the last, I agree with him to the extent that I presently have an opinion on them. But Sellars is a scientific realist, encapsulating this realism in the dictum: “to have good reason for holding a theory is ipso facto to have good reason for holding that the entities postulated by the theory exist” ([2], p. 91).