Alfred Jules Ayer (1910– ) was born in London and educated at Eton and Christ Church, Oxford. He attended sessions of the logical positivist ‘Vienna Circle’ in 1932, and taught at Oxford from 1933 until joining the Army in 1940. His Language, Truth and Logic was published in 1936, and The Foundations of Empirical Knowledge in 1940. After war service he returned to Oxford in 1945, and became Grote Professor of the Philosophy of Mind and Logic at University College, London, the following year. The Problem of Knowledge was published in 1956. In 1959 he returned to Oxord as Wykeham Professor of Logic, a post he held until his retirement in 1977. He had been made a Fellow of the British Academy in 1952, and was knighted in 1970. Among his publications after he returned to Oxford are The Concept of a Person (1963), Philosophical Essays (1965), The Origins of Pragmatism (1968), Metaphysics and Common Sense (1969), Russell and Moore: the Analytical Heritage (1971), Probability and Evidence (1972), The Central Questions of Philosophy (1973), and Philosophy in the Twentieth Century (1982).