Signs vs. Causes? An epistemological approach to prognosis in the Latin Middle Ages

From the 12^th century onwards, prognostic disciplines were part and parcel of the Latin ordo scientiarum. This is true for astrology and divination as well as for medicine and weather forecasting. While scholarly research has focused very much on the moral discussions of knowledge of the future in the Middle Ages, the epistemological challenge of integrating this form of knowledge into a coherent theoretical framework has been neglected so far. This article shows how the traditional account of prognostic disciplines as sign-based forms of knowledge was revised and refined during the 13^th century in the light of new philosophical (Aristotelian) and also theological paradigms. As a result of this, Latin philosophers and theologians established important criteria which allowed for a clear-cut epistemological distinction between different forms of prognostic signs and thus radicalized the discussion about the legitimacy of some prognostic disciplines.