If Saint Thomas Aquinas was a great theologian, it is in no small part because he was a great philosopher. And he was a great philosopher because he was a great metaphysician. In the twentieth century, metaphysics was not much in vogue, among either theologians or even philosophers; but now it is making a comeback, and once the contours of Thomas's metaphysical vision are glimpsed, it looks like anything but a museum piece. It only needs some dusting...