movement according to ibn sīnā and abū al-barakāt baghdādī

according to abū al-barakāt baghdādī, time and place are a priori conditions of motion; moreover, against the peripatetic philosophers, for whom time is the measure of motion, he holds that time is the measure of existence. nevertheless, he believes that we can define motion on the basis of our intuitive non-scientific concept of time and, by so doing, we can resolve the apparent circularity of the aristotelian definition of motion. concerning the mode of existence of motion, avicenna presents two notions of motion: motion as an intermediary state (ḥarakat bi-maʿnā al-tawassuṭ) and motion as the transversal of a given distance (ḥarakat bi-maʿnā al-qaṭʿ). he believes that motion defined by the first notion is a mental construct, while motion defined by the second notion has a real existence. against the objections to the second notion, abū al-barakāt believes that motion cannot be merely mental, even if its existence is momentary and unstable. concerning the cause of motion, abū al-barakāt agrees with avicenna that the cause of motion cannot be the moving body itself. in this article, the two philosophers’ views on the unity of motion and the contrariety of motions are also discussed.