The transcendental method...does not try to prove that genuine knowledge is possible; rather, it presupposes that it is. Then it asks, What must the world, the mind and human thought be like if this presupposition is true? The transcendental method then goes ahead to ask what the necessary conditions of human knowledge are. The answer must first of all must be the existence of the God of Scripture. To Van Til, this principle was not only a fact, but an argument for the existence of God. Without God there is no meaning (truth, rationality, etc.); therefore, God, exists.
John Frame Apologetics to the Glory of God, pg. 70