In fact it then appears that the argument for the Scripture as the infallible revelation of God is, to all intents and purposes, the same as the argument for the existence of God. Protestants are required by the most basic principles of their system to vindicate the existence of no other God than the one who has spoken in Scripture. But this God cannot be proved to exist by any other method than the indirect one of presupposition. No proof for this God and for the truth of his revelation in Scripture can be offered by an appeal to anything in human experience that has not itself received its light from the God whose existence and whose revelation it is supposed to prove. One cannot prove the usefulness of the light of the sun for the purposes of seeing by turning to the darkness of a cave. The darkness of the cave must itself be lit up by the shining of the sun. When the cave is thus lit up each of the objects that are in it “proves” the existence and character of the sun by receiving their light and intelligibility from it.
– Cornelius Van Til, The Defense of the Faith p.130-131
‘For with you is the fountain of life;
in your light do we see light.’ – Psalm 36