How can God know the future if future things are not actual? Would there be time if no change were to occur in the universe? What allows us to identify a direction in the order of changes independently of the series of instants in time? Aquinas answers all these questions in his commentary on Aristotle's Physics.According to him, only entities located in the present exist. The present is nothing but the intermediate between past and future points on the line of time. Time, in turn, is ontologically dependent on change, but despite being its measure, it is mind-independent: time is what...