TURING, Alan Mathison (1912-1954). 'Practical forms of type theory.' Offprint from: The Journal of Symbolic Logic, vol. 13, no. 2. Princeton, NJ: 1948. 8° (254 x 175mm). 18pp., 79-94. (last leaf faintly creased.) Stapled self wrappers (front wrapper detached and slightly chipped). Provenance: ALAN TURING (his presentation inscription on upper cover to:) -- R.B. Braithwaite (occasional pencil marginalia).

EXTREMELY RARE PRESENTATION COPY. Richard Bevan Braithwaite (1900-1990), philosopher of science, first met Turing at King's College, Cambridge, in 1933. Braithwaite, as a fellow of King's, asked Turing to deliver a paper 'Mathematics and Logic' to the prestigious Moral Science Club. Braithwaite continued to be interested in Turing's work, requesting an offprint of 'On Computable Numbers'. In January 1952, Turing recorded an episode of the Brains Trust for BBC radio with Braithwaite and Max Newman. 'Braithwaite's own work was in the Cambridge tradition of scientifically informed philosophy exemplified by Bertrand Russell, J. M. Keynes, Frank Ramsey, and C. D. Broad. His mathematical training showed most clearly in his philosophy of science, notably in his explication of the concept of probability invoked in modern science. This culminated in Scientific Explanation (1953) ... a classic work whose influence ranks him as a methodologist of science with Sir Karl Popper and Carl Hempel' (ODNB). Newman 1948b.

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