Tetrabiblos
Introduction
Tetrabiblos (from the Greek τετράβιβλος, "four books"), also known in Latin as Quadripartitum, is a text on the philosophy and practice of astrology, written in the 2nd century AD by the Alexandrian scholar Claudius Ptolemy. Ptolemy's Almagest was an authoritative text on astronomy for more than a thousand years, and the Tetrabiblos, its companion volume, was equally influential in astrology, the study of the effects of astronomical cycles on earthly matters. But whereas the Almagest, as the critic Isaac Casaubon noted, holds the stars as objects of admiration and reverence, the Tetrabiblos considers them as subjects of a possible divinatory science.
Content
The Tetrabiblos is divided into four books. The first book, as Ptolemy explains, treats of the "qualities of the time, whether continuous or interrupted, and the methods by which one can predict future events." The second book addresses the "effects of the aspects of the Sun, Moon, and planets on the terrestrial world and its inhabitants." The third book concerns "the consideration of the effects of the lunar and solar cycles on the earth and its inhabitants," and the fourth book is about "the consideration of the effects of the fixed stars."
Influence
The Tetrabiblos was a significant work in the history of astrology, offering a comprehensive treatment of the subject and establishing a robust theoretical framework. Its influence extended into the Middle Ages and the Renaissance, and it continues to be studied today in academic circles and by practitioners of astrology.