“In other words, the non-Christian needs the truth of the Christian religion in order to attack it. As a child needs to sit on the lap of its father in order to slap the father’s face, so the unbeliever, as a creature, needs God the Creator and providential controller of the universe in order to oppose this God. Without this God, the place on which he stands does not exist. He cannot stand in a vacuum.”
Cornelius Van Til, Essays on Christian Education (The Presbyterian and Reformed Publishing Company: Phillipsburg, NJ, 1979).