Philosophy gives a proof for the existence of God; the science of apologetics gives the motives for believing in Christ, the Son of God; but all the incontrovertible proofs they offer fall short of the certitude that actually comes to a convert through the gift of Faith. Imagine a young man whose father has been lost for years. A friend, returned from a trip, assures him that he has certain evidence that his father really exists on another continent. But the young man is not fully satisfied with the evidence, however convincing it is; until he is restored to his father’s actual presence, he will not have peace. So it is with conversion: before, one knows about God; afterward, one knows God. The first knowledge the mind has is notional and abstract; the second is real, concrete, and it becomes bound up with all one’s sentiments, emotions, passions, and habits.
--Archbishop Fulton J. Sheen, Peace of Soul, 1949