A. J. Ayer - Works

Works

Ayer is best known for popularising the verification principle, in particular through his presentation of it in Language, Truth, and Logic (1936). The principle was at the time at the heart of the debates of the so-called Vienna Circle which Ayer visited as a young guest, and others including the leading light of the circle, Moritz Schlick were already offering their own papers on the issue. Ayer's own formulation was that a sentence can only be meaningful if it has verifiable empirical import, otherwise it is either "analytical" if tautologous, or "metaphysical" (i.e. meaningless, or "literally senseless"). He started work on the book at the age of 23 and it was published when he was 26. Ayer's philosophical ideas were deeply influenced by those of the Vienna Circle and David Hume. His clear, vibrant and polemical exposition of them makes Language, Truth and Logic essential reading on the tenets of logical empiricism– the book is regarded as a classic of 20th century analytic philosophy, and is widely read in philosophy courses around the world. In it, Ayer also proposed that the distinction between a conscious man and an unconscious machine resolves itself into a distinction between 'different types of perceptible behaviour', an argument which anticipates the Turing test published in 1950 to test a machine's capability to demonstrate intelligence (consciousness).

Ayer wrote two books on the philosopher Bertrand Russell, Russell and Moore: The Analytic Heritage (1971) and Russell (1972). He also wrote an introductory book on the philosophy of David Hume and a short biography of Voltaire.

In 1972–1973 Ayer gave the Gifford Lectures at University of St Andrews, later published as The Central Questions of Philosophy. In the preface to the book, he defends his selection to hold the lectureship on the basis that Lord Gifford wished to promote '"Natural Theology", in the widest sense of that term', and that non-believers are allowed to give the lectures if they are "able reverent men, true thinkers, sincere lovers of and earnest inquirers after truth". 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.

In "The Concept of a Person and Other Essays" (1963), Ayer heavily criticized Wittgenstein's private language argument.

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 1950s work of common language philosophy. Ayer responded to this in the essay "Has Austin Refuted the Sense-data Theory?", which can be found in his Metaphysics and Common Sense (1969).