Unidad documental simple 64 - Notes by J. N. Keynes entitled 'Dodgson's problem'

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Refers to the fallacy involved in the regarding of proposition if A then not C as the contradictory of the proposition if A then C. Refers to the second edition of his Formal Logic, and to a third edition of the latter, which he is working on. Refers to an accompanying slip [not included]. Sets out an argument, involving an equation including Q, R, X, Y and K, and claiming that it is not valid. Concludes that if X is Y, then and are not both true, but that one cannot infer absolutely that and are not both true.

Perhaps relating to correspondence between C. L. Dodgson and Sidgwick in Mar 1894 regarding a logic problem: see ADD.MS.c/93/106-108 and ADD.MS.c/100/93