The encyclopedists and their disciples declared themselves satisfied, inasmuch as psychological experts had done away with the absurd traditions of the Middle Ages as well as antique superstitions. The death penalty for demonidolatry was removed, but the doors of the insane asylum opened for its followers. Could any better arrangement have been made at the present day? Let us take the history of this famous epidemic of demonidolatry of other days and examine the documentary evidence offered against those accused of the crime of sorcery, passing the testimony through the crucible of modern science, pathology, physiology, together with all observable symptoms, holding in view meanwhile modern neurological discoveries; let us strive, in a word, to solve this great psychological question, which has greatly agitated the human understanding for four hundred years past. We believe _what is, is the truth_, and in order to best judge the facts narrated, it is well to first arrange our knowledge as to the psychological condition of Occidental populations during the Middle Ages, a condition that was only the continuation of the ideas and traditions of antiquity, modified by the fanatical prejudices of a new religion and by a cruel and barbarous social Constitution. If history authorizes us, in fact, to conclude that the occult sciences have existed from the earliest periods of antiquity, that the people who brought learning from the Orient to the Occident, have at all times admitted the existence of genii, angels, and demons, it is easy to explain the action that such mysterious traditions would have on the ignorant minds of the peasantry of the Middle Ages, bowed under the yoke of slavery to feudal Lords and the clerical despotism of the Romish Church. Let us interrogate these historical texts with impartiality, and analyze these ancient theogonies, which are, so to speak, the _proces verbaux_ of the philosophic development of the human mind, and we shall see whether we can admit that mental diseases may prevail _epidemically_ for several generations, like the pestilential maladies of the fourth century, for example. We know that it was in India, the cradle of human genius, that the doctrine of supernaturalism, of good and bad spirits exerting an occult influence on mankind, was born. Ancient history shows such a belief goes back to antique times. Zoroaster, inspired by _Ahura Mazda_, the Omniscient, wrote, in the Zend Avesta, the text and commentaries of the religious law dedicated to the Aryas of India and Persia. This law had for its object the destruction of the cult of _dews_ or demons, who infested the earth under human forms, and also to repress the naturalistic instinct of the most ancient people of _Asia_, by initiating them in a faith for Celestial genii.