Astrology

During the early Middle Ages, astrology, like many ancient disciplines, languished in the Latin West less because of the church's condemnation than because few Westerners were able to draw an astrological chart or read Greek astrological works. The most important theoreticians and practitioners in the early Middle Ages were Arabic speakers in the Islamic world. Arabs developed several astrological ideas later accepted in the West, such as the correlation of patterns in human history with the conjunctions of Jupiter and Saturn, the so-called great conjunctions. Greek and Arabic works of astrological theory were translated into Latin only in the twelfth and thirteenth centuries. Medieval intellectuals like Albertus Magnus (c. 1200–1280) and Roger Bacon (c. 1220–1292) endorsed astrology but faced the problem of reconciling astrological determinism with the Christian doctrine of free will. They claimed that the stars influenced only the body, and not the soul. St. Thomas Aquinas (c. 1224–1274) conceded that the stars influenced human passions, and that many astrological predictions were correct because most people were ruled by their passions. He claimed, however, that the wise man could resist his passions, and thus the stars could not determine his actions. The medieval emphasis on the power of the stars over the body helped astrology become closely allied with medicine. Charles V of France (r. 1364–1380), whose library contained many books Map of Tycho Brahe's system of planetary orbits around the earth, with signs of the horoscope (1660–1661), by Andreas Cellarius. Danish astronomer Brahe, who calculated the measurements of the solar system in the sixteenth century, was one of the last major Western astronomers to practice astrology. © STAPLETON COLLECTION/CORBIS on astrology, contributed to the foundation of a college of astrological medicine in the 1360s.

Not all late medieval intellectuals accepted the new astrology. Six propositions of Bishop Étienne Tempier's famous prohibition of 1277 condemned astrology, mostly on the grounds of its determinism. The Scholastic philosopher Nicole d'Oresme (c. 1325–1382) vigorously opposed astrology. He reiterated the Christian attack on astrological determinism and added a new argument, that the velocities of the heavenly bodies were mathematically irrational and incommeasurable, and thus it was impossible to know them exactly enough for astrology to work.