This second series of Gifford Lectures was delivered in the University of Aberdeen in April and May, 1965. Once again I thank the Principal and his colleagues for all their kindness to my wife and myself which made our stay such a very happy one; and I especially thank Professor V. C. Wynne-Edwards for allowing me again to give the lectures in his Department of Natural History where I used myself to teach when I held the Regius Chair before him.

As before, I found the informal seminars I held a help in clarifying the expression of my ideas and I thank both those who took part in the discussions and Dr. Michael Begg who again acted as chairman. The lectures are published in the same general form in which they were delivered but each has been somewhat expanded to give a slightly fuller treatment or to add some further quotations to illustrate the theme. As my study of religion is that of a naturalist, I have, in providing examples of the many different elements involved, made more quotations in this series of lectures than in the last; there is therefore a special section of acknowledgements at the end of the book (p. 249).