Alfred Jules Ayer (A J Ayer) was born in 1910 in St John's Wood, London, to a wealthy family. His mother was from the family who founded the Citroën car company and his father was a Swiss Calvinist financier who worked for the Rothschild family. He was educated at Ascham, St Vincent's Preparatory School and Eton. He went on to study classics at Christ Church, Oxford where he won a scholarship.
In 1936 he published Language, Truth, and Logic, a book which established him as a leading philosophical thinker and writer. He was the Grote Professor of the Philosophy of Mind and Logic at University College London from 1946 until 1959, when he became Wykeham Professor of Logic at the University of Oxford. He was president of the Aristotelian Society from 1951 to 1952. He was knighted in 1970.
He died in June 1989.