Frank Ramsey on Induction: Why Validity Is the Wrong Standard

Frank Ramsey's treatment of induction starts from a general account of inference. He argues that premises and conclusion alone do not fully specify an inference. It also needs the rule by which the conclusion is drawn. This holds for deductive and inductive arguments alike, though the rule differs in kind between them. Deductive rules preserve truth. Inductive rules do not. Inductive rules are judged instead by how reliably they extend belief from observed cases to unobserved ones. This three-part account of inference sets the terms within which Ramsey's treatment of induction, probability and laws should be read.Quote from Ramsey: ‘Logic as the science of argument and inference is traditionally and rightly divided into deductive and inductive; but the difference and relation between these two divisions of the subject can be conceived in extremely different ways.’Deductive argumentQuote from Ramsey: ‘formal deduction does not increase our knowledge, but only brings out clearly what we already know in another form; and that we are bound to accept its validity on pain of being inconsistent with ourselves’Quote from Ramsey: ‘deduction on the other hand is merely a method of arranging our knowledge and eliminating inconsistencies or contradictions.’Inductive argumentQuote from Ramsey: ‘it is impossible to represent it [inductive argument] as resembling a deductive argument and merely weaker in degree; it is absurd to say that the sense of the conclusion is partially contained in that of the premisses. We could accept the premisses and utterly reject the conclusion without any sort of inconsistency or contradiction.’Ramsey holds:‘whenever I make an inference, I do so according to some rule or habit. An inference is not completely given when we are given the premiss and conclusion; we require also to be given the relation between them in virtue of which the inference is made.’‘the rule of the inference determines for us a range to which the frequency theory can be applied