The Thomistic Institute Astrology: Why Did Medieval Philosophers Study It? – Fr. Ambrose Little, O.P.
Nov 7, 2025
Fr. Ambrose Little, a Dominican priest and director of the Thomistic Institute, dives into the fascinating world of medieval astrology. He explains how medieval philosophers viewed astrology as a legitimate branch of natural philosophy intertwined with science. Ambrose contrasts ancient beliefs with modern views, highlighting how astrology was seen as a means to study celestial influences on earthly matters. He discusses St. Augustine’s critiques, the role of free will, and warns against the dangers of demonic deception in divination, ultimately asserting that astrology lacks scientific validity today.
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Astrology Was Part Of Medieval Natural Philosophy
- Medieval philosophers studied astrology because it was integrated with natural philosophy and astronomy.
- Science and philosophy were essentially the same discipline in the Middle Ages, so astrology fit as a study of nature.
Astrology Covered Natural Effects, Not Only Horoscopes
- Medieval astrology encompassed any study of how heavenly bodies caused effects on Earth, not just horoscopes.
- Tides, tanning, and weather forecasting were all considered astrological subjects.
Geocentrism Made Heavens Causally Relevant
- Aristotle's geocentric cosmology made the heavens causally relevant to sublunary change.
- Medieval thinkers inherited the view that superlunary motions sustain and influence terrestrial motion and change.
