F.P. Ramsey was a remarkably creative and subtle philosopher who in the briefest of academic careers (he died in 1930 at 26) made significant contributions to logic, philosophy of mathematics, philosophy of language and decision theory. His few published papers reveal him to be a figure of comparable importance to Russell, Carnap and Wittgenstein in the history of analytical philosophy. This book is the first critical study of Ramsey's work, offering a thorough exposition and interpretation of his ideas, setting the ideas in their historical context, and assessing their significance for contemporary research. The study is intended to complement the reissue by the Press of Ramsey's papers edited by Professor Hugh Mellor.