Ramsey Frank Plumpton (1903–30), influential British philosopher of logic and mathematics. His primary interests were in logic and philosophy, but decades after his untimely death two of his publications sparked new branches of economics, and in pure mathematics his combinatorial theorems gave rise to ‘Ramsey theory’ (Economic Journal 1927, 1928; Proc. London Math. Soc., 1928). During his lifetime Ramsey’s philosophical reputation outside Cambridge was based largely on his architectural reparation of Whitehead and Russell’s Principia Mathematica, strengthening its claim to reduce mathematics to the new logic formulated in Volume 1 – a reduction rounded out by Wittgenstein’s assessment of logical truths as tautologous. Ramsey clarified this logicist picture of mathematics by radically simplifying Russell’s ramified theory of types, eliminating the need for the unarguable axiom of reducibility (Proc. London Math. Soc., 1925). His philosophical work was published mostly after his death. The canon, established by Richard Braithwaite (The Foundations of Mathematic. . . , 1931), remains generally intact in D. H. Mellor’s edition (Philosophical Papers, 1990). Further writings of varying importance appear in his Notes on Philosophy, Probability and Mathematics (M. C. Galavotti, ed., 1991) and On Truth (Nicholas Rescher and Ulrich Majer, eds., 1991).
As an undergraduate Ramsey observed that the redundancy account of truth ‘enables us to rule out at once some theories of truth such as that ‘to be true’ means ‘to work’ or ‘to cohere’ since clearly ‘p works’ and ‘p coheres’ are not equivalent to ‘p’.’ Later, in the canonical ‘Truth and Probability’ (1926), he readdressed to knowledge and belief the main questions ordinarily associated with truth, analyzing probability as a mode of judgment in the framework of a theory of choice under uncertainty. Reinvented and acknowledged by L. J. Savage (Foundations of Statistics, 1954), this forms the theoretical basis of the currently dominant ‘Bayesian’ view of rational decision making. Ramsey cut his philosophical teeth on Wittgenstein’s Tractatus Logico- Philosophicus. His translation appeared in 1922; a long critical notice of the work (1923) was his first substantial philosophical publication. His later role in Wittgenstein’s rejection of the Tractatus is acknowledged in the foreword to Philosophical Investigations (1953).
The posthumous canon has been a gold mine. An example: ‘Propositions’ (1929), reading the theoretical terms (T, U, etc.) of an axiomatized scientific theory as variables, sees the theory’s content as conveyed by a ‘Ramsey sentence’ saying that for some T, U, etc., the theory’s axioms are true, a sentence in which all extralogical terms are observational. Another example: ‘General Propositions and Causality’ (1929), offering in a footnote the ‘Ramsey test’ for acceptability of conditionals, i.e., add the if-clause to your ambient beliefs (minimally modified to make the enlarged set self-consistent), and accept the conditional if the then-clause follows. See also BAYESIAN RATIONALITY, PROBA- BILITY, TRUT. R.J.
