The germ of this book first took shape as four Forwood Lectures on the philosophy of religion, which were delivered in the University of Liverpool in 1949. It developed into two series of Gifford Lectures given in the University of St. Andrews in the years 1950 and 1951. After a long process of rewriting it has reached its final form in the present work. I have to thank these two Universities for affording me an opportunity—and a stimulus—to express my views on this topic; and although I have tried to eliminate turns of phrase more suited to a lecture than to a book, I have done my best not to depart from the ideal common to both the benefactions by which I have been favoured—that of being intelligible to educated men and women who are not professional philosophers.
It is impossible for me to acknowledge adequately my indebtedness to previous writers on these subjects or to the many colleagues and pupils with whom I have had discussions; but I must thank Miss M. J. Levett, my former colleague in Glasgow, for her critical but kindly comments on my arguments and style, and also for reading the proofs. I am grateful to Professor H. D. Lewis for some valuable suggestions made at the last moment before going to press; and I must also tender my thanks to Mrs. A. Heywood, to Miss Nancy Melville, and especially to my wife, for the care and skill with which so many different versions have been typed.
In a book of this kind it may not be out of place to express also my indebtedness to my parents—to my mother for introducing me to a living religion at the most tender age possible, and to my father for introducing me, at an age only a little more advanced, to a lucid, humane, and rational theology as well. However little I may have profited, I have at least had the advantage of thinking about religious problems as soon as I was able to think at all.