Language, Truth and Logic

A short, combative manifesto that brought the ideas of the Vienna Circle to English readers, written by Ayer in his mid-twenties after a stay in Vienna. Its central tool is the verification principle: a statement is literally meaningful only if it is either true by definition or can in principle be checked by experience. The first chapter, on the elimination of metaphysics, uses this test to dismiss claims about a reality beyond experience as nonsense. Ayer then argues that philosophy is the analysis of language, not the discovery of special truths, and that logic and mathematics are tautologies that say nothing about the world. Later chapters give a phenomenalist account of material objects, the self and other minds. The best-known chapter, a critique of ethics and theology, presents moral judgements as expressions of feeling rather than statements of fact, a view later called emotivism, and treats talk of God as neither true nor false. Critics soon pointed out that the verification principle seems to fail its own test.

It is the clearest and liveliest statement of logical positivism, and its arguments about meaning, metaphysics and ethics still frame many debates.