Keynes and philosophers

The chapter discusses the development of Keynes’s philosophical thought, from his early trust in human rationality, attested by the logical theory of probability, to his late discovery that human action rests on convention, which is central to the General Theory. Treatise on Probability is a typical product of early XXth century Cambridge philosophy, which draws inspiration from Moore’s ethics and Russell’s logical positivism. The book fell into oblivion when the underlying philosophy became outmoded, though recent scholarship has rightly called attention to side issues of the book, weight in particular, that are relevant to Keynes’ economics. Except for his acceptance of Ramsey’s critique, Keynes had no opportunity to reconsider his early philosophy. His relationship with the later Wittgenstein is shrouded in mystery, and Keynes’s convention lacks the solidity that social practice and tradition confer on Wittgenstein’s uses and rules. If Keynes’s convention has no direct and precise philosophical matrix, when it comes to economic method Keynes’s indebtedness to Marshall is incontrovertible, but often neglected. Both authors felt that mathematical and statistical reasoning was of limited utility in economics, and disliked the extremely simplifying assumption of the economic man. They also shared the fundamental view that economics falls within the moral sciences and must rely on common sense and ordinary language.