Vatican Heresy Trials and the Separation of Astrology from Astronomy

The Roman Inquisition's prohibition of astrology as heresy forced scholars to strip spiritual interpretation from their work, a move that inadvertently shaped modern empirical science. Once unified, astronomy and astrology diverged as the Vatican deemed judicial astrology—which predicted human behavior as preordained—a threat to the Catholic doctrine of free will. The Inquisition, established in 1542 to combat apostasy, witchcraft, and blasphemy, targeted intellectuals and created the Index Librorum Prohibitorum, listing astrological books as heretical. Giordano Bruno, who embraced heliocentrism and mysticism, was burned at the stake for heresy. Tommaso Campanella, a Dominican friar and judicial astrologer, was tortured and imprisoned for 27 years after predicting the deaths of Vatican and Spanish royalty. These cases terrified the scientific community. Galileo Galilei, who once cast horoscopes for income, abandoned the practice and removed astrology from his astronomical work. As a result, astronomy became a purely mathematical and geometric field, escaping censorship. Universities across Europe removed astrology from their curricula during the 17th century, and new academies in London and Paris rejected it as superstition. The article argues that astrology's decline was driven not by telescopic evidence but by fear of persecution, and speculates that without the Inquisition, astrology might be more influential today.