Abstract

Ancient Peripatetics and Neoplatonists had great difficulty coming up with a consistent, interpretatively reasonable, and empirically adequate Aristotelian theory of complete mixture or complexion. I explain some of the main problems, with special attention to authors with whom Avicenna was familiar. I then show how Avicenna used a new doctrine of the occultness of substantial form to address these problems. The result was in some respects an improvement, but it also gave rise to a new set of problems, which were later to prove fateful in the history of early modern philosophy.