Sir Alfred Jules Ayer was for many years a member of the Council of the Royal Institute, and gave generously of his help and advice. It was therefore particularly fitting—while appropriate, in any case, for one of the most distinguished British philosophers of this century—that the Institute should devote its annual lecture series of 1990–1991 to his memory; and it is on these lectures that the essays in this volume are based.

The first lecture, ‘A Defence of Empiricism’ by Ayer himself, was written to be given to the closing plenary session of the quinquennial World Congress of Philosophy held in Brighton in 1988. He was not well enough to travel from the south of France to be present at the Congress, but very readily gave his permission for the lecture to be read for him. We judged that he would have been equally pleased for it to be read again as the first in the series of his own memorial lectures. It is printed here for the first time with the kind permission of his executors, Lady Ayer and Professor Ted Honderich.

We have also included in this volume the transcript of a broadcast interview with Ayer by Ted Honderich, now printed for the first time. We are most grateful to Professor Honderich for making this available to us.