Tetrabiblos

Tetrabiblos is a text on the philosophy and practice of astrology, written in the 2nd century AD by the Alexandrian scholar Claudius Ptolemy (c. AD 90–c. AD 168).

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 But whilst the Almagest as an astronomical authority was superseded by acceptance of the hel...