No Reagent, No Reaction: The Barren Transmission of Avicennan Dynamics to Ḥasdai Crescas

Important features of the new Avicennan physics were available to Ḥasdai Crescas in al-Tabrīzī’s commentary on Maimonides’ twenty-five premises, a book that he thoroughly exploited for his assault on the Aristotelian world-view. However, in his discussion of the thirteenth premise, which maintains quies media, Crescas chose to ignore al-Tabrīzī’s arguments, which rest on the concept of mayl or inclination. The article examines the treatments of this premise by Crescas and al-Tabrīzī, within the wider context of the transmission of Avicennan physics to Europe. This study furnishes additional evidence for Crescas’ lack of interest in some of the new ideas in physics as well as his failure to develop a coherent theory of time and motion. The appraisals of impetus theory by older and newer historians of science are also discussed. An appendix provides some raw evidence for the classification of spiral motion as simple—a view that may have come to Crescas’ attention as well.