A. J. Ayer is the best-known British philosopher of the generation that followed Bertrand Russell. At age twenty-four Ayer published Language, Truth and Logic (1936), a vigorous polemical attack on views he dismisses as "metaphysical." The opening sentence declares that "The traditional disputes of philosophy are, for the most part, as unwarranted as they are unfruitful," and the rest of the work is similarly iconoclastic. The book made Ayer's name and influenced the course of philosophical debate for decades. It has been translated into at least fourteen other languages, making his views known worldwide. A later book, The Problem of Knowledge (1956), also became a classic text. Ayer was the last in a line of distinguished British empiricists: his philosophical approach and interests are in the tradition of John Locke, George Berkeley, David Hume, John Stuart Mill, and Russell. It is a measure of Ayer's standing that his name is...