Is Astrology a Type of Divination? Thomas Aquinas, the Index of Prohibited Books, and the Construction of a Legitimate Astrology in the Middle Ages and the Renaissance

What is the relationship between astrology and divination? In particular, is astrology a type of divination, as is often asserted or assumed? In both astrology and divination, knowledge and prediction of the future are primary goals, but does this warrant calling astrology a form of divination? I approach these questions by exploring the response of Thomas Aquinas, which was to be extremely influential for many centuries. First I analyze in some detail Thomas’s answer in his Summa theologiae 2-2.92–95; then I discuss two significant sixteenth-century examples of its influence: the 1557, 1559, 1564, and later indexes of prohibited books; and Pope Sixtus V’s anti-divinatory bull, Coeli et Terrae Creator (1586). In this way, we can explore some of the complex historical dynamics at play in the construction of a legitimate astrology in the Middle Ages and the Renaissance.