ONTOLOGICAL ARGUMENT The ontological argument attempts to prove from the very concept of God that God exists: if God is conceivable, then he must actually exist. This argument was formulated by Anselm and defended by Scotus, Descartes, Spinoza, Leibniz, and, in modern times, Norman Malcolm, Charles Hartshorne, and Alvin Plantinga, among others. We shall examine the Anselmian argument. Anselm (1033–1109) wanted to find a single argument that would prove not only that God exists, but also that he