Stuk 64 - Notes by J. N. Keynes entitled 'Dodgson's problem'

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.