Thomas Aquinas rejected it, and among theologians his authority has prevailed ever since. But among philosophers it has had a better fate. Descartes revived it in a somewhat amended form; Leibniz thought that it could be made valid by the addition of a supplement to prove that God is possible. Kant considered that he had demolished it once for all. Nevertheless, in some sense, it underlies the system of Hegel and his followers, and reappears in Bradley’s principle: “What may be and must be, is.”
