How can I be certain about something? This project investigates the ideal of epistemic stability in medieval philosophical and theological debates.



Like their ancient predecessors, medieval philosophers were interested in the stability of cognitive objects. They paid particular attention to the presence of one’s own soul, which they took to be a stable substance, and contrasted it with the presence of changing material objects. It is therefore important to assess their theories of self-knowledge and to look at the way they explained both the soul itself and the cognitive access we have to it. Moreover, medieval philosophers were also strongly interested in stable cognitive states. Inspired by theological debates, they evaluated special cases (e.g. Adam’s cognition before the fall, the cognition of separated souls after death) that were supposed to show what kind of cognition a stable and highly reliable state could yield. An analysis of these cases will make clear how medieval Aristotelians distinguished between stable and unstable states and why they thought that perfect cognition requires stability. The stability both of cognitive objects and states played a crucial role in their assessment of knowledge, for knowledge requires certainty on both sides: an object has to be certain and it has to be certain to a cognitive agent. But as soon as any doubt arises, certainty is in jeopardy. An investigation of both sides of certainty will reveal how medieval philosophers attempted to distinguish knowledge from mere opinion and faith.

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