"_incubi_" and "_succubi_" seek and obtain carnal intercourse with human beings,[43] we discover already in the ideas of the first Christian centuries the elements of the sorcery of the Middle Ages. And when we read further the accusations which the first Christian sects hurled against one another,--when we learn that the party which was raised by the Council of Nice to the orthodox position accused the Gnostics, Marcionites and Arians of devil-worship, confederacy with Satan and sorcery, we meet already here that union of heresy and sorcery by which the Church of the Middle Ages acquired such a fearful weapon against dissenters,--a union which must not be looked upon as a mere casual invention of wickedness and theological hatred, but as the necessary consequence of the whole dualistic theory of morals, as the necessary fruit of the belief in devils. A long time must have been required for the festivals common to the natural religions of Europe to become extinct or be remodelled into Christian form. The external practices by which religious ideas obtain a sensuous expression, possess generally more tenacious power of existence than the ideas themselves, and continue in existence when these have disappeared, as the shell after the death of the nautilus. In certain religions of natural development adoration of the sun and the moon are the most important. Among the Celtic, Germanic and Slavic tribes, as before among Hebrews and Phoenicians, these divinities of the light were adored by kindling fires, by sacrifices and banquets on mountains and in groves, especially at the time of the vernal equinox (Easter), at the beginning of May (Valpurge's night), and on the night of the summer solstice. From the fact that traces of the custom still exist in our own day, though its original significance is lost, we can all the more safely assume that it continued to exist without interruption, openly at first, then in secret, retaining its significance, in spite of the efforts of spiritual and profane authorities to extirpate it, and assuming more and more in the popular mind that character of devil-worship with which the Church has branded these reminiscences, from heathen times. And when finally it ceased entirely, or was changed into seasons of popular festivity which had no dangerous suggestiveness even in the eyes of the Church, still the remembrance of the demoniacal festivals of mountain and grove must have been inherited from generation to generation, and then it was but another step to believe that they still continued and were participated in by persons who practiced magical arts, and had been invested with the suspicious wisdom of the ancient valas and druids--the female seers and physicians of the pagans. That the notion of the Witches' Sabbath, which was celebrated on the night before the first of May, and of the paschal journey of the witches to Blokulla have this historical origin is very probable.