mysterious fact that it is there at all, that it exists. Here Aquinas develops ideas not only from Aristotle and Boethius but from medieval → Jewish philosophy (Maimonides [1135–1204]) and → Islamic philosophy (esp. Avicenna [980–1037] and Averroës [1126–98]) to take an original—and, for some, supremely important—philosophical position. Here as elsewhere (e.g., his Christological account of what individuates a created nature, or his eucharistic treatment of substance, dimension, and space), Thomas’s