Abstract
Protestantism is habitually seen by the catholic against the background of pluralism, whereas to the pro testant, catholicism is monolithic. The author on the contrary, seeks to show the profound unity which animates protestantism, compared with the diversity of catholicism. It is especially concerned with the operation of this plurality of forms throughout the unity of religion, as also with the tendency to institu tionalise the religious phenomenon whereby church and sect appear as phases. Herein lies a very rich field of development for religious sociology, in the sphere of theory no less than at the practical level.