When you come to knowing God, the initiative lies on His side. If He does not show Himself, nothing you can do will enable you to find Him. And, in fact, He shows much more of Himself to some people than to others—not because He has favourites, but because it is impossible for Him to show Himself to a man whose whole mind and character are in the wrong condition. Just as sunlight, though it has no favourites, cannot be reflected in a dusty mirror as clearly as a clean one.
— C.S. Lewis, Mere Christianity