As with extrabiblical Catholic doctrine in general, the doctrine of purgatory originated in Church Tradition—through, among other things, statements by 1) the allegorist Origen, who believed in the pre-existence of souls and the salvation of Satan; 2) Tertullian, who became a Montanist (a member of a second-century ascetic sect); 3) Augustine; and 4) Gregory I (Pope 590-604), whose stories relating to his visions of the afterlife (see his Dialogues) became important for developing the doctrine during