This paper was read by Michael Dummett at Leiden University on September 26, 1992 at the invitation by Göran Sundholm to address the topic mentioned in the title. Dummett’s lecture was part of a workshop, Meaning Theory and Intuitionism, with 12 invited speakers over three days. After the workshop, Dummett gave a copy of the manuscript to Sundholm together with permission to publish it. At the time, nothing came of the publication plans, nor did Dummett publish it in any other form. The text has remained virtually unknown, and apart from a lecture of Per Martin-Löf, also at Leiden, on the same topic (published in this journal), it has received no scholarly attention. We are indebted to Dummett’s literary executor, Professor Ian Rumfitt, of All Souls College, Oxford, who after nearly three decades confirmed the earlier permission to publish.

Göran Sundholm

Ansten Klev