Magnetism and Bradwardine’s rule of motion in fourteen and fifteen century treatises
Résumé
In his Tractatus de proportionibus, Thomas Bradwardine describes some devices consisting
of a magnet and pieces of iron, in order to put his rule of motion to the test. These
devices, or similar ones, are also found in the Questiones super libros Physicorum of
Nicole Oresme, and in three works by Blasius of Parma, namely the Questiones de
ponderibus, the Questiones super libros Physicorum and the Questiones circa Tractatum
proportionum. In this paper, I describe these devices, while examining the theory of
magnetism that is in use and I analyse how the arguments on magnets demarcate the
field of application of the rule of motion.