Those interested in what the narrator of Walker Percy?s Love in the Ruins calls “the dread chasm that has rent the soul of man ever since the famous philosopher Descartes ripped body loose from mind and turned the very soul into a ghost that haunts its own house” will find plenty to be getting on with in this excellent little book. The Proof of God is a narrative of ideas, beginning in the thickets of medieval theology and cutting a clean path toward modernity: here, digestibly, is the story of how human reason separated itself from God, and of how the Cartesian blade came down at last between res cogitans (the mind) and res extensa (everything else). In 1078, Saint Anselm assembles his Ontological Proof, in which man?s capacity to conceive of a perfect Being is adduced as proof of that Being?s existence. Schopenhauer will one day categorize this as ?a charming joke,? but it holds water for 150 years — until the Franciscan monk William of Ockham enters, with his famous razor of reduction: “What can be explained by the assumption of fewer things is vainly explained by the assumption of more things.” Ockham initiates the slow severing of the divine from Western consciousness, and soon enough we arrive at scrupulous, black-wigged Descartes, dubitating everything but the fact of his own doubt. The Proof of God wraps up a trifle hurriedly, the final chapter accelerating past Bertrand Russell?s atheism toward that Martian moment when Ludwig Wittgenstein recognizes all ideas as ?language-games.? Then again, perhaps a sort of empty whizzing sensation, as the mind of Western man finally rounds upon itself, is not altogether inappropriate.