ABSTRACT
This chapter suggests that Bertrand Russell was inspired by John Maynard Keynes. Keynes developed a theory of probability which interprets degrees of probability as degrees of logical relevance, and published it in 1921 in his A Treatise on Probability. In fact, Keynes’ idea that a probable inference is a partial logical entailment is echoed by Russell’s greatest student, Ludwig Wittgenstein. Russell’s emphasis on the relational aspect of logic was fundamental to Keynes’ theory of probability, though Keynes extended the scope of logical relations to include non-demonstrative inference. Besides Russell, Keynes is the only seminal thinker in 1912 who interprets probability as logical relevance. He is the only one who construes the theorem of indifference as a theorem of irrelevance. Pitt Taylor’s 1897 legal treatise, published in London, is one Keynes could have read while Keynes was at Cambridge University studying legal cases for his Treatise.
