The story of the history of Western astrology begins with the philosophers of Greece in the 5th century BC. the Greeks added numerology, geometry and rational thought. The philosophy of Plato and later of the Stoics made astrology respectable, and by the time Ptolemy wrote his textbook the Tetrabiblos, in the second century AD, the main lines of astrological practice as it is known today had already been laid down. In future centuries astrology shifted to Islam only to return to the West in medieval times where it flourished until the shift of ideas during the Renaissance.