Ayer was the Grote Professor of the Philosophy of Mind and Logic at the University College London from 1946 until 1959, when he became Wykeham Professor of Logic at the University of Oxford. He was knighted in 1970.

Ayer received an education in the humanities at Eton College, and served in the British military during World War II, working in military intelligence for a time. He was a noted social mixer and womanizer, and was married four times, including to Dee Wells and Vanessa Lawson (nee Salmon). Reputedly he liked dancing and attending the clubs in London.

He was a friend of Isaiah Berlin.

Ayer was an avowed atheist, and followed in the footsteps of Bertrand Russell by debating with the Jesuit scholar Frederick Copleston on the topic of religion.

Ayer was closely associated with the British humanist movement. He was an Honorary Associate of the Rationalist Press Association from 1947 until his death. In 1965, he became the first president of the Agnostics' Adoption Society and in the same year succeeded Julian Huxley as president of the British Humanist Association, a post he held until 1970. In 1968 he edited "The Humanist Outlook", a collection of essays on the meaning of humanism.

He taught or lectured several times in the United States, including serving as a visiting professor at Bard College in the fall of 1987. At a party that same year held by fashion designer Fernando Sanchez, Ayer, then 77, confronted Mike Tyson harassing Naomi Campbell. When Ayer demanded that Tyson stop, the boxer said: "Do you know who the fuck I am? I'm the heavyweight champion of the world," to which Ayer replied: "And I am the former Wykeham Professor of Logic. We are both pre-eminent in our field. I suggest that we talk about this like rational men" (Rogers 1999:344).

Shortly before his death in 1989 he received publicity after having an unusual near-death experience, which some erroneously interpreted as a move away from his lifelong and famous religious skepticism.

Works
In some ways, Ayer was the philosophical successor to Bertrand Russell, and he wrote two books on the philosopher: Russell and Moore: The Analytic Heritage (1971) and Russell (1972). He also wrote an introductory book on the philosophy of David Hume.

Ayer is perhaps best known for his verification principle, as presented in "Language, Truth, and Logic" (1936), according to which a sentence is meaningful only if it has verifiable empirical import. He started work on the book at the age of 24 and it was published when he was 26. Ayer's philosophical ideas were deeply influenced by those of the Vienna Circle. His clear, vibrant and polemical exposition of them makes Language, Truth and Logic essential reading on the tenets of logical positivism -- the book is regarded as a classic of 20th century philosophy, and is widely read in philosophy courses around the world.

In 1972-73 Ayer gave the Gifford Lectures at University of St Andrews, later published as The Central Questions of Philosophy. He still believed in the viewpoint he shared with the logical positivists: that large parts of what was traditionally called "philosophy" - including the whole of metaphysics, theology and aesthetics - were not matters that could be judged as being true or false and that it was thus meaningless to discuss them. Unsurprisingly, this made him unpopular with several other philosophy departments in this country and his name is still reviled by many British professors to this day.

In "The Concept of a Person and Other Essays" (1963), Ayer made several striking criticisms of Wittgenstein's private language theory.

Ayer's sense-data theory in Foundations of Empirical Knowledge was famously criticised by fellow Oxonian J. L. Austin in Sense and sensibilia, a landmark 1950's work of common language philosophy. Ayer responded to this in the essay "Has Austin refuted the sense-date theory?", which can be found in his Metaphysics and Common Sense (1969).