Ayer, A(lfred) J(ules) (1910–1989)

English philosopher. He wrote Language, Truth and Logic (1936), an exposition of the theory of ‘logical positivism’, presenting a criterion by which meaningful statements (essentially truths of logic, as well as statements derived from experience) could be distinguished from meaningless metaphysical utterances (for example, claims that there is a God or that the world external to our own minds is illusory). He was knighted in 1970.