deny a material cause of the universe, but must also refer creation’s temporal origin. According to Bonaventure (c. 1217–1274) and Aquinas’s teacher Albert the Great (d. 1280), the universe began to exist after not existing and the doctrine of creation ex nihilo is incompatible with the view that the universe is eternal. Aquinas took a more subtle approach. He argued that there is nothing inherently contradictory in the view that the universe is eternal, although we should be cautious about the use