1. H. B. Curry, ‘The Inconsistency of Certain Formal Logics’, The Journal of Symbolic Logic
7 (1942), 115–117. Also, H. B. Curry and R. Feys, Combinatory Logic,North-Holland Publ. Co., Amsterdam, 1958, pp. 258–262.
2. This formulation of the paradox is essentially the same as that given in my book, Symbolic Logic,Ronald Press, New York, 1952, pp. 258–262. The present essay does not attempt to present all the details of the system S, or even to describe it in exactly the way it is described there, but rather this essay outlines some of the leading ideas involved in the proof of the consistency of S, especially as these ideas can be developed in connection with the newly proposed restriction of nonrecurrence. There is no discussion of such topics as general subproofs or reiteration. The conventions regarding quotation marks are assumed to be the same, in principle, as those used in most of my papers in The Journal of Symbolic Logic.H
3. Symbolic Logic, op. cit,pp. 109–111.
4. Symbolic Logic, ibid,pp. 106–109.
5. D. Prawitz, Natural Deduction,Almqvist & Wiksell, Stockholm, 1965, pp. 94–97.