Marcel Mauss (1872-1950) never completed his Doctoral thesis on prayer. Yet his scarcely mentioned introduction (Books I and II) of 176 pages and privately printed in 1909, can be seen as some of his most important work. His argument that much of prayer is a social act will be of great interest to anthropologists, sociologists and theologians.Here, the first English translation to be published, is preceded by a general introduction by W.S.F.Pickering and finally a specific commentary on Mauss's use of ethnographic material.