Abstract

The bulk of this book is the second series of John Dewey Lectures, delivered by Professor Ayer in April 1970. To this, Ayer has added a criticism of Roy Harred’s purported refutation of Hume and a chapter about "non-truth-functional" conditionals that rounds out the lectures. Leaving Harred aside, this book provides an elegant, concise, and up-to-date introduction to the problem of induction and related issues concerning probability. Hume is here vindicated. Beginning by giving what may be the best, updated paraphrase of Hume’s negative argument about causal judgments, Ayer explicates the subsumed atomicity, the denial of natural necessity, and the claimed vacuity or circularity of introducing the "uniformity of nature." Ayer goes on to distinguish a priori or logical probabilities, statistical or frequency judgments, and credibility or ground floor inductive judgments, and he summarily argues that the admissibility of the first two forms of judgment, properly understood, provides no real justification for credibility judgments, which, though not defined as subjective, turn out to need some support from our decision to project and therefore entrench certain predicates, or take as lawlike certain generalizations, rather than others. Ayer here includes a very clear explication and criticism of Carnap’s way out in the Logical Concept of Probability, and elsewhere. Ayer acutely summarizes and discusses the Hempel and Goodman paradoxes, taking a position substantially in agreement with Quine and Goodman, and welds this discussion into a Humean conclusion: "In a certain sense cases are what we choose them to be. We do not decide what facts habitually go together but we do decide what combinations are to be imaginatively projected. The despised savages who beat gongs at solar eclipses to summon back the sun are not making any factual error. It is a true generalization that whenever they beat the gongs the sun does shine again, and if they always keep up the ceremony, it is also a true generalization that the sun comes out again only when they beat the gongs. If we despise them, it is because they tell a fictional story about what would happen if they did not beat the gongs, which we do not accept. They see what goes on as well as we do; it is just that we have a different and, we think, a better idea of the way the world works." To say all this is just, of course, to summarize and refurbish Hume’s position on causality. But to do that has two very real values now: 1) It underlines and exposes the epistemic basis of the position taken by Hume’s heirs; 2) It makes clear what are the departures required if one is to differ in substance from Hume and Ayer.—J. L.