Astrology

As in other ancient sciences, Renaissance humanists claimed to be recovering the true, ancient astronomy from corruption by Arab and medieval Latin writers (although Arab-derived great conjunction theory remained very popular.) Renaissance philosophers, particularly those influenced by Neoplatonism, also extended the discipline's scope. The third book of Marsilio Ficino's (1433–1499) Three Books on Life (1489) treated the planets as a guide to all aspects of human life. Girolamo Cardano (1501–1576), who wrote a commentary on the Tetrabiblios, scandalized many by drawing a natal horoscope of Jesus Christ. While Martin Luther (1483–1546) and John Calvin (1509–1564) both condemned astrology, many of their Protestant followers (including Philipp Melanchthon; 1497–1560) practiced it. Protestant astrologers were particularly interested in reconciling astrology with the apocalyptic interpretation of the Bible, using the stars and great conjunctions to help predict the date of the end of the world.

Astrology was an important support for professional astronomers in the late Middle Ages and Renaissance, as many patrons were interested in astronomical data principally for its astrological uses. The leaders of the scientific revolution differed in their opinions of astrology. The last major Western astronomers to seriously practice astrology were Tycho Brahe (1546–1601) and Johannes Kepler (1571–1630), both of whom drew horoscopes for the monarchs they served. Mechanical philosophers like Marin Mersenne (1588–1648) and the "Christian Epicurean" Pierre Gassendi (1592–1655) denied the doctrine of the influence of the stars on the Earth that astrology was based on, as it had no mechanical explanation. Although several of the founding members of the Royal Society practiced astrology, it lost its central intellectual role in the late seventeenth century. Astronomers increasingly justified their science as useful in navigation and cartography rather than astrology. Copernican astronomy did not "dis-prove" astrology, but the shift from an earth-centered to a sun-centered cosmos did call into question traditional geocentric astrological interpretation. Astrology also suffered from the general decline of magical thinking as Europe entered the eighteenth century. Although many ordinary people continued to believe in astrology, it was not taken seriously by most scientists and intellectuals.