The Myth of Formal Logic

some inductive inferences are as probable in relation to the premisses as non-sceptics think they are. But the premisses of my proofs were, principally, statements of logical probability; and propositions of this kind, or at least the published systems of propositions of this kind, lie under certain definite objections from philosophers, as well as under a less definite but even more damaging suspicion. So, although my purposes in this book are entirely polemical and critical, and I therefore neither have attempted nor will attempt anything systematic enough to be called a theory of logical probability, the arguments of Part One cannot possibly receive a fair hearing, unless I can show that the objections commonly entertained against the theory of logical probability are mistaken. This, and this alone, is the reason for the existence of Part Two. The theory of logical probability is itself, however, only one form, though certainly the most ambitious form, that nondeductive logic has assumed; and some at least of the objections which have been made to it are equally objections to nondeductive logic in any form. In addition to that, even those objections which are peculiar to the theory of logical probability all stem, I believe, from mistakes about the relation between nondeductive and deductive logic, or from mistakes about deductive logic itself. For these two reasons, while my main object in this Part is to defend the arguments of Chapters V-VII, by defending the theory of logical probability, a considerable proportion of what follows is not about the theory of logical probability specifically, but about non-deductive logic in general; and this in turn required that considerable attention be devoted to deductive logic itself. IX