Though Keynes's philosophical thinking was originally thought to derive principally from his single published philosophical work, the Treatise on Probability (Harrod, 1951; Braithwaite, 1975), there has always been good reason to doubt that Keynes adhered unhesitatingly to his early views after he had turned from philosophy to economics. Indeed on two occasions in the 1930s when his thinking about economics was undergoing significant change, Keynes explicitly said that he thought he had been mistaken about key positions he had earlier taken on philosophical subjects. First, in 1930 he allowed that Ramsey had in an important respect been correct in his criticism of Keynes's intuitionism in the Treatise (Keynes, X, pp. 338–9). Second, he granted in his 1938 “My Early Beliefs” memoir that he and the others who had enthusiastically espoused Moore's Principia views in Keynes's first years at Cambridge had seriously underestimated the importance of rules in moral life (Keynes, X). Unfortunately, on neither of these occasions was Keynes particularly clear regarding just what these admissions implied concerning what he still accepted and what he had then come to reject among his former positions. Indeed, his response to Ramsey's criticism was so brief that scholars have been unable to agree whether it represented a major reversal or minor modification in Keynes's thinking about probability (cf., e.g., Bateman, 1987 and O'Donnell, 1989).