The three lectures contained in this volume were given under the auspices of the University of London, at King’s College, London, in the Michaelmas Term, 1935. They are printed substantially as delivered, with only a minimum of revision. I have added as an appendix a paper which was read as a presidential address to the Oxford Society of Historical Theology on October 24, 1935. It will be printed according to custom in the Transactions of the Society. I am grateful to the committee and members of the Society for their consent to this anticipatory publication.