Jon McGinnis

The forma fluens/fluxus formae debate concerns the question as to whether motion is something distinct from the body in motion, the flow of a distinct form identified with motion , or nothing more than the successive states of the body in motion, the flow of some form found in one of Aristotle's ten categories . Although Albertus Magnus introduced this debate to the Latin West he drew his inspiration from Avicenna. This study argues that Albertus misclassified Avicenna's position, since Albertus could not conceptualize motion at an instant, whereas it is claimed here this was the very position Avicenna adopted. The paper includes an overview of Albertus's discussion and a brief survey of the Avicennan sources upon which Albertus drew. The heart of the paper treats Avicenna's analysis of motion at an instant. Avicenna's general argument was that since spatial points have no extremities, nothing in principle prevents a moving object from being at a spatial point for more than an instant, understood as a limit. It is then argued that Avicenna had the philosophical machinery to make sense of a limit, albeit not in mathematical terms, but in terms of an Aristotelian potential infinite

Aristotle's account of place in terms of an innermost limit of a containing body was to generate serious discussion and controvery among Aristotle's later commentators, especially when it was applied to the cosmos as a whole. The problem was that since there is nothing outside of the cosmos that could contain it, the cosmos apparently could not have a place according to Aristotle's definition; however, if the cosmos does not have a place, then it is not clear that it could move, but it was thought to move, namely, in its daily revolution, which was viewed as a kind of natural locomotion and so required the cosmos to have a place. The study briefly outlines Aristotle's account of place and then considers its fate, particularly with respect to the cosmos and its motion, at the hands of later commentators. To this end, it begins with Theophrastus' puzzles concerning Aristotle's account of place, and how later Greek commentators, such as Alexander of Aphrodisias, Themistius and others, attempted to address these problems in what can only be described as ad hoc ways. It then considers Philoponus' exploitation of these problems as a means to replace Aristotle's account of place with his own account of place understood in terms of extension. The study concludes with the Arabic Neoplatonizing Aristotelian Avicenna and his novel introduction of a new category of motion, namely, motion in the category of position. Briefly, Avicenna denies that the cosmos has a place, and so claims that it moves not with respect to place, but with respect to position