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Expresses his gratitude for Henry Sidgwick's 'unremitting kindness', his constant help and the advice and encouragement, which have meant so much to him in his work. Expresses his heartfelt sympathy with Nora in her loss.

Thanks Nora on behalf of himself and his wife for the copy of Henry Sidgwick: A Memoir, and declares how much he is looking forward to reading it and to learning more 'of one whom he admired and revered more than any other person [he has] ever known.' Is pleased to hear that [The Principles of] Political Economy is 'selling steadily'; suggests that an index would be useful. Offers to supervise its creation, and states that it would be well for him to see '[W.E.?] Johnson at an early stage in order to ascertain the lines on which he is proceeding.' Thanks her for sending him the cheque, and declares that he does not believe that he has any claim to it, and would rather should consist in feeling that he had carried out a wish expressed by one to whom he owed so much. Asks her not to think ill of him for returning it, and suggests that part of it might be used 'as the remuneration of Johnson for making the index.'

Admits that he may have spoken too strongly [see 94/63] 'in implying that the method of Reductio ad absurdum would necessarily be formulated as If P then Q If P then not Q _ not P' Refers to two enclosed examples (included) 'in which this would seem the natural analysis.' Claims to be unable to 'find any good case (except from Geometry) of the method.' Would like to send to Sidgwick 'a good case of such an argument', but cannot find one. Letter accompanied by examples of two of Euclid's proposals in which the method of reductio ad absurdum is used, both involving geometry.

Refers to an enclosed solution of the 'puzzle of hypotheticals' [included], which he believes to be 'perfectly satisfactory'. Claims to show that 'the two hypotheticals, alleged to be contradictory, are not in reality incompatible with one another.' Use such propositions as "If X is Y, H is K" and IF X is Y, H is not K" and the method of Reductio ad absurdum to illustrate his theory. Concludes by expressing the hope that he has succeeded in making his position clear to Sidgwick. Letter is accompanied by the solution purporting to demonstrate the fallacy regarding the above two propositions.

Accompanied by a card from W. E. Johnson to Henry Jackson dated 2 Feb. 1903.

Easter Term 1905.