  Given these fascinating debates, it is no wonder that Marchia’s physical theories drew the attention of medieval and modern scholars alike. The first important study on Marchia’s thought was Anneliese Maier’s partial edition and analysis of book IV, q. 1, of Marchia’s Sentences commentary (Maier 1940; critical edition Marchia 2006b; version from Vat. lat. 943 in Marchia 2006c). There Marchia puts forth his famous forerunner to John Buridan’s impetus theory of projectile motion. Aristotle had not provided a satisfactory explanation for why, when we throw a ball, for example, the ball keeps going even after we have released it. Marchia’s explanation was that we leave behind a force in the ball — a virtus derelicta — that keeps the ball in motion. The fact that this force was temporary rather than permanent meant that it was not akin to the inertia theory of classical mechanics, but, as Marchia stated explicitly, it was a simple theory and did explain the phenomena in temporary projectile motion.