The Principles of Demonstrative Induction

Abstract

Some years ago I wrote two articles in Mind on Induction and Probability, and, more recently, in my presidential address to the Aristotelian Society I tried to state as fully and clearly as I could the present position of the logical theory of what Mr. Johnson calls ‘Problematic Induction’. In the present paper I propose to do the same for what he calls ‘Demonstrative Induction.’ In the former undertaking I was greatly indebted to Mr. Keynes, and in this I am even more indebted to Mr. Johnson. All my raw material is contained in his work on Logic, and I can claim no more than to have beaten it into a more coherent shape than that in which he left it. I think that my approach to the subject by way of the notions of Necessary and Sufficient Conditions has certain advantages, and that I have been able to make some extensions of the theory. This must be my excuse for publishing a rather long and tedious essay on a somewhat hackneyed subject which has been treated so fully and so recently by a logician of Mr. Johnson’s eminence.