 The argument asks one to posit some actually infinite ray, AB and then another actually infinite ray, AC, so as to form an acute angle ∠BAC. Next Avicenna asks one to consider the gap, BC, between the two rays. The farther from A that BC is, the larger BC becomes. Since the two rays are actually infinitely extended, BC should, in principle, also be actually infinite; however, BC always lies between AB and AC and of necessity terminates at them, so BC is finite. Thus, there is a contradiction: BC is both finite and infinite and, claims Avicenna, what produced the contradiction is the assumption that there is actually infinite space. Whether Avicenna’s new argument is successful became a matter of intense debate in post-classical Islamic natural philosophy, with such notables as Abū l-Barakāt al-Baghdādī (1080–1165) and Najm al-Dīn al-Kātibī al-Qazwīnī (ca. 1203–1277) finding it wanting, whereas Naṣīr al-Dīn al-Ṭūsī (1201–1274) and Mullā Ṣadrā (1571–1636) considered it defensible (McGinnis 2018). 