Astrology and the Sibyls: John of Legnano's De adventu Christi and the Natural Theology of the Later Middle Ages

Argument Medieval authors adopted a range of postures when writing about the role of reason in matters of faith. At one extreme, the phrase “natural theology” (theologia naturalis) was used, largely pejoratively, to connote something clearly inferior to revealed theology. At the other end, there was also a long tradition of what one might term “the impulse to natural theology,” manifested perhaps most notably in the embrace of Nature by certain twelfth-century authors associated with the school of Chartres. Only in the fifteenth century does one find authors using natural reason to investigate religious truths who also employ the term “natural theology,” now in a positive light, for their activities. Among such thinkers, astrology and eschatology frequently played an important role. In that respect, the writings of fourteenth-century Bolognese jurist John of Legnano offer an important example of the place of astrological, prophetic, and apocalyptic material in late medieval natural theology. In his 1375 treatise De adventu Christi, Legnano demonstrated that ancient poets, pagan seers such as the Sibyls, and non-Christian astrologers had all predicted, like Old Testament prophets, the virgin birth of Christ. For Legnano, not simply was Creation part of God's revelation, but, equally importantly, the very categories of reason and revelation blur in a way that points toward the works of Renaissance humanists and lays a foundation for a model of natural vaticination that showed reason's capability to reach fundamental religious truths.