This in-depth study on missions and non-Christian religions, worldviews, and ideologies was written by Hendrik Kraemer (1888–1965), professor of religions at Leiden University from 1937 to 1947, who had previously, from 1922 to 1937, served as a Bible translator and missionary in the Dutch East Indies, today Indonesia. Kraemer wrote this study at the request of John Mott, then chairperson of the IMC. For the only time in mission history, a single volume written by a single person helped prepare for a great international conference.