Mediaeval astrology has long suffered a neglect which, judged intrinsically, it deserves. Little more than a romantic interest now attaches to a complex divinatory art that for centuries has been looked upon as one of the aberrations of the human mind. When viewed historically, however, astrology is seen to have occupied a place in art and philosophy which many a later science might envy, and which, consequently, it is not well to ignore. Ancient astrology, indeed, has already received in recent years close and appreciative study. The poem of Manilius has never lost its appeal for the classicist; and the prominence of astrological thought in ancient philosophy and ethics has frequently aroused the curiosity of scholars. A history of mediaeval astrology, on the other hand, still remains to be written.