This encyclopedia is a comprehensive survey and analysis of the main philosophical, scientific (or empirical), and theological studies of mission in the 19th and 20th centuries. It deals with (1) the names, (2) the concepts, (3) the methods, and (4) the branches of missiology. Therefore, it concludes with four chapters after an introductory chapter. Since most branches of missiology only came into existence in the 19th century, most analyses, descriptions, and bibliographies do not go back beyond 1800. Both the philosophy of mission and the science of mission are dealt with in this first volume. The theology of mission, especially the missionary theology, is thoroughly discussed in the second volume.