St. Anselm, the eleventh century bishop of Canterbury, is famous for his “ontological proof” for God. Anselm tried to show that there was no way that God can’t exist. The idea of God, Anselm reasoned, is the idea of a being “than which none greater can be conceived.” When the atheist and the theist deny and affirm God’s existence respectively, it is this idea that they have in mind. But since it is better for a being to have existence than for it to lack it, and since God is, by definition, the best, the conclusion is inescapable: God necessarily exists. It is no more possible, logically, to affirm the idea of God while simultaneously denying His real existence than it is possible to affirm the definition of a “bachelor” while denying that a bachelor is an unmarried man.