This extended essay presents the meditations of an eminent scholar on medieval philosophical theology. Beginning with a discussion of faith and reason, Ramon M. Lemos argues that we can be practically justified in accepting certain religions even though we may not know that their central claims are true. Lemos moves on to his operational definition of God, based on St. Anselm's concept of God as a being that which no greater can be conceived. From this ground, he considers various medieval arguments for the existence of God and refutes the ability of the major arguments to succeed in demonstrating God's existence. He concludes that it is impossible to demonstrate the existence of God philosophically. This provocative book addresses the fundamental issues in the philosophy of religion—from a Christian perspective—while maintaining the necessary intellectual distance between revealed theology and philosophy.