Two letters from Maurice L'Abbé [1920-2006, Canadian mathematician], University of Montreal ], and two copy replies from Turing.
/1 In Abbe's first letter (22 March) discusses his review of Turing's "Practical forms of type theory" [which had been published in the Journal of Symbolic Logic 13, 1948]. He discusses Turing's axiom of extensibility, and formulae in detail. /2 Turing's initial response (26 April) provides explanation of his formulae. /3 Abbé's reply of 30 May 1949 encloses a draft of his review and asks for comment (to be published Journal of Symbolic Logic), /4 Copy letter 3 Jun 1949, Turing to Alonzo Church, Princeton University, say Abbé is "not quite right" in his correction, /5 copy letter to Abbé 3 June 1949, says feels that he "appears to me to prove too much", and explains why.