The belief that one’s future could be learned by observing the stars was equally widespread. Astrologers throve at the courts of kings, and sometimes their advice was taken even by him whose every act was held to be under special divine direction. It would be a great mistake to think that the astrologer was maintained merely for the amusement of king and court, like the jester. His utterances were taken most seriously, and the principles of his art were so generally accepted as to become the commonplaces of the thought and the conversation of daily life. In 1305, for instance, when certain cardinals urged Pope Clement V to return to Rome, they reminded him that every planet was most powerful in its own house.[1] Indeed, even in our speech to-day numerous vestiges of the astrological art survive.[2] Moreover, a grander and more imposing witchcraft displayed itself in the stories of the wizard Merlin and in the persons of the wicked magicians with whom knights contended in the pages of mediæval romance. So strong was the tendency to believe in the marvelous, that men of learning were often pictured by subsequent tradition, if not by contemporary gossip, as mighty necromancers. Even Gerbert, who seems to have done nothing more shocking than to write a treatise on the abacus and build a pipe-organ, was pictured as running off with a magician’s book and daughter, hanging under bridges between earth and water to escape noxious spells, and making compacts with Satan.[3] The attitude of the average mind as it has just been illustrated was to a large extent characteristic of the best instructed and most widely read men. The erudite poet Dante accepted the influence of the constellations upon human destiny. Bodin maintained in his _Republic_—perhaps the greatest book on political science written during the sixteenth century—that astrology was very useful in tracing the development of society.[4] Aquinas, chief of the mediæval theologians, accepted astrological theory, except as limited by human free will, and further admitted that most men make little use of their liberty of action but blindly follow their passions, which are governed by the stars.[5] Among other great mediæval churchmen and canonists, d’Ailly and Gerson both believed that God signified important events in advance through the stars, and d’Ailly made some astrological predictions himself. Astrology was much taught in the mediæval universities,[6] and was regarded as the climax of mathematics and as an essential part of medicine.