There are, I imagine, five considerations that will serve as a point d'appui to the future historian of our century's philosophy, aiding him to interpret with fair adequacy the working faith and working postulates of one large and influential group of present thinkers. The members of this group, he will point out, however much they differ in other respects, accept in common and act upon this five-fold assumption, namely, that progress in philosophy depends upon (i) it abandoning its traditional claim to being systematic and final, in favour of “more modest” attempts at the piecemeal solution of particular problems; (ii) these piecemeal attempts being conceived as essentially co-operative undertakings, calling for assistance from men of science no less than from philosophers, so that (iii) the character of philosophical research is broadly not very dissimilar to that of scientific research; that this, in turn, necessitates (iv) an abandonment of the claim to, and the search for, “necessary” and certain knowledge, and an acceptance of knowledge that is probable as rationally sufficing; from all of which it follows, lastly, as something very like a corollary, that (v) philosophers can deal profitably only with “hypothetical questions,” seeking to discover, from certain things provisionally taken as true, what other things may or must also be true. It is by these methodological convictions, by some declared, by others not, that much of the best work in Britain and America during this first third of our century has been inspired.