From the Middle Ages until the present, the development of astrology among Jews was associated mainly with the name of Abraham Ibn Ezra (1089–1167). His scientific corpus deals with mathematics, astronomy, scientific instruments and tools, and the Jewish calendar; but especially with astrology. This volume is the first product of a larger enterprise—a scientific edition of all twelve Ibn Ezra’s astrological treatises—and offers a critical Hebrew text of the two versions of Ibn Ezra’s Sefer ha-Te'amim, the Book of Reasons, accompanied by an annotated translation and commentary. The two treatises presented here were designed by Ibn Ezra to offer “reasons”, “explanations”, or “meanings” of the raw astrological concepts formulated in the introduction to astrology that Ibn Ezra entitled Reshit Hokhmah (Beginning of Wisdom).