I am grateful to the University of Edinburgh for the honour it did me in inviting me to deliver Gifford Lectures during the academic year 1979–1980. My wife and I received much hospitality from friends and members of the University, summed up in the kindly reception by the Principal and Mrs Burnet. Particularly too I should thank Miss Margaret Ewing, who organized our visits, Peter Malakoff who helped with the preparation of the manuscript, and Michiko Yusa who did much valuable work in assisting with the bibliography and also in preparing the manuscript. I am grateful too for support from the University of California, Santa Barbara, and from the University of Lancaster. My wife Libushka motorized my pilgrimages to Edinburgh, and made much of all this writing possible. I dedicate the book to my brother Alastair and his family: though he was raised, like me, partly in Glasgow, Edinburgh was also a city of inspiration for him.
Santa Barbara, California
26 June 1980