Amicus medicorum, 1496
Jean Ganivet's Amicus medicorum, or "friend of physicians," is a seminal work on astrological medicine. Divided into four sections of seven chapters each, the work casts multiple horoscopes. The most notable horoscope, seen here, was cast in 1431 for the ailing dean of Vienne to determine whether or not he would die. After consulting the chart, Ganivet predicted he would die, and he indeed did two days later. Astrologers (and astronomers) employed different types of horoscopes. Judicial astrology predicts circumstances and events for specific people. A nativity is a horoscope constructed for a specific person at the time of his or her birth. Mundane astrology examines the celestial influences on more general world events, particularly the prediction of natural phenomena. The employment of astrology as a basis for medical advice (or a prediction of mortality) has always been controversial in the western tradition. Church authorities have always assailed astrology as an attempt to diminish God's omnipotence and a threat to human free will. Despite the Christian argument, most people during the Renaissance nevertheless accepted astrology as a medical diagnostic and prognostic tool. However, constructing horoscopes for some high-status people could be dangerous and even illegal. It was illegal, for instance, for anyone to construct a horoscope for Queen Elizabeth I of England, unless authorized by the Court.