This collection of essays on the work of Sir Karl Popper is based on the Royal Institute of Philosophy's annual lecture series given in London from October 1994 to March 1995. Popper himself died in August 1994, shortly before the start of the lectures. His death was the cause of sadness to all of those involved in the series. Some, indeed, had been close friends of Popper over many years, and others colleagues and acquaintances, some close, some more distant. Even those unacquainted with Popper personally spoke in their lectures of the profound intellectual stimulation they had received from the study of his works.

Towards the end of the course of planning the lecture series, I did, with some trepidation, contact Popper. His reaction was at once generous and self-effacing. Having initially told me that he did not envy me my task of getting speakers, when he saw the outline programme, he wrote that ‘the plans for the course on my philosophy were very interesting: much more interesting than I thought possible’. Credit here should be given where it is really due. Once the Royal Institute determined on the topic, both subjects and speakers suggested themselves naturally; and there was no difficulty in persuading potential contributors from Britain to participate. Popper himself suggested that Günter Wächtershäuser from Munich and Hubert Kiesewetter from Eichstatt should be added to the original list of British-based contributors, and this was done.