This book is one of the most famous post-classical astrological works. The author William Lilly obviously has very good instincts. His famous prediction of the Great Fire of London in 1666 was so accurate that some people suspected that he was his initiator, and he was later found not guilty. Lilly also uses astrology in medical practice. This book discusses the use of astrology in diagnosing diseases and determining whether patients will die or get better. This book was first published in 1647 as Christian astrology.