 The last condition, which amounts to the denial of naturalism, goes back to a paper that Russell wrote for Sidgwick in 1893, “The Relation of What Ought to be to What Is, Has Been or Will Be” (RoE: 37–40/Papers 1: 213–214). Russell observes that “from the point of view of formal logic” it is impossible to derive an Ought from an Is. This leads him to the conclusion that “some one or more propositions ethical in form must be regarded as axiomatic unless [and this is a big ‘unless’] such propositions are materially equivalent to some assertion about what is, has been or will be”. By “materially equivalent” he seems to mean “mean the same as”. Thus morality might not hang from the skyhook of intuited axioms if moral judgments meant the same as natural judgments of some kind. But he goes on to argue against this possibility, that is, to argue that what Moore was to call naturalism is false. Nor is it odd that he should have anticipated Moore, since Sidgwick, who was their teacher, anticipated them both.