"Physic without astrology is like a lamp without oil."
Astrological medicine was an important tool in medieval times. Many doctors were trained astrologers who incorporated astrology into the healing arts for assistance with diagnosis, prognosis, and even treatment. Astrologer-doctors had many different tools they could utilize in their craft to help the human body overcome diseases, but the focus of many of these astrologer-doctors was on preventative medicine.
Through the examination of a birth chart, an astrologer could identify the types of illnesses the individual would likely struggle with throughout their life. With this piece of information, the astrologer could prescribe foods, medicines, or regimens to combat these potential afflictions.
While preventative care was the primary goal in the medieval healthcare system (a focus shared by many ancient medical systems) astrology could be used as a powerful diagnostic tool. By using the time of the patient's first becoming ill or the first time the physician meets with the patient, the astrologer-doctor is able to ascertain the type, cause, and prognosis of the illness. With this information the treatment process is expedited and astrology can be used again to elect the time to begin or conduct treatments.
Astrology and medicine had a mutually beneficial relationship throughout the medieval period. Astrology provided medicine with a methodology of diagnosis and treatment, and medicine provided astrology with a shield. With no shortage of critics throughout history, astrology would likely not have survived as long or remained so intact if it weren't for its intimate relationship with medicine.
While many critics could not entertain the idea of astrology accurately predicting events from a birth or horary chart, the value of astrological medical techniques was not denied and was, in fact, put in a different category of supposedly acceptable astrology. This new category was called "natural astrology" and contained medical, weather prediction, and general electional techniques. The second type of astrology was "judicial astrology" and contained all other branches of the art. Judicial astrology would suffer countless attacks from critics on ethical, theological, and technical grounds, but critics were notably silent when it came to astrology and medicine.