^{Page 120 of note} * I do not know whether Mr. Keynes has considered and rejected a definition of irrelevance which, prima facie, would be simpler than his. He does not state definitely whether every pair of propositions has some probability-relation, but I think he does not hold this view. I think he would say, e.g., that there is no probability-relation between the propositions ‘2+2=4’ and ‘Napoleon disliked poodles.’ If so, it would seem natural to define h as irrelevant to a when a/h does not exist.

^{Page 124 of note} * I take this opportunity to protest against Mr. Keynes’s practice of alluding to Principia Mathematica as though I were the sole author. Dr. Whitehead had an equal share in the work, and there is hardly a page in the three volumes which can be attributed to either of us singly.