We know that the poet Hesiodus in his theogony, that Plato, from the time of his initiation with the Hermetic doctrines, that Aristotle in his philosophical works, all admit the existence of immaterial beings interesting themselves in the affairs of humanity. The Pythagorians, on their side, affirmed their power of controlling demons by keeping themselves in constant meditation, abstinence and chastity.[50] During all times of antiquity, there were corporations of priests, philosophers, theosophists, thaumaturgists and other sects, who exercised the trade of invoking spirits by conjuring them with charms, by enchantments and witchcraft, and changing by their aid the laws of nature, to command the elements and accomplish other extraordinary feats. In order to do these prodigies they had recourse to cabalistic formulæ, indicated in conjuring books, or by incantations, magical circles, or simply by magnetic power. Simon of Samaria, Circe, Medea, Plotinus, Porphyrius, Jamblichus, and the famous Canidie, so justly cursed by Horace, belonged to this clan of magicians, gnostics, enchanters and mediums, who acquainted the people with the occult arts of the magi of Chaldea. It is only necessary to study history to be convinced of this fact. Damis, the historian and pupil of Apollonius of Tyana, has left us the biography of his master, the most remarkable thaumaturgist of antiquity. It is in this work that he shows that while Apollonius was lecturing on philosophy at Ephesus, he stopped in the midst of his speech and cried out to the murderer who, at the same moment, assassinated Domitian at Rome, “Courage, Stephanus; kill the tyrant!” Apollonius had sojourned long in India, and all his disciples have attested the marvelous things he could do. He cured incurable diseases and made other miracles that astonished his contemporaries who were partisans, like himself, of the doctrines of Pythagoras. Porphyrius published the fifty-four treatises of his master Plotinus, the illustrious neoplatonist, a work in which we find all the ideas of contemporaneous experimental psychology and a mystical philosophy supported on extasy, contemplation and hypnotism—ideas which were again enunciated one day by the enchanter Merlin, Albertus Magnus, Pic de la Mirandolle, Lulle, Cornelius Agrippa, Count Saint Germain, Joseph Balsamo, Robert Fludd, Richard Price and the _freres_ of _Rose Croix_.