Suppose we think of a man made of water in an infinitely extended and bottomless ocean of water. Desiring to get out of water, he makes a latter of water. He sets this ladder upon the water and against the water and then attempts to climb out of the water. So hopeless and senseless a picture must be drawn of the natural man’s methodology based as it is upon the assumption that time or chance is ultimate. On his assumption his own rationality is a product of chance. On his own assumption even the laws of logic which he employs are products of chance. The rationality and purpose that he may be searching for are still found to be products of chance. So then the Christian apologist, whose position requires him to hold that Christian theism is really true and as such must be taken as the presupposition which alone makes the acquisition of knowledge in any field intelligible, must join his “friend” in his hopeless gyrations so as to point out to him that his efforts are always in vain.
It will then appear that Christian theism, which was first rejected because of its supposed authoritarian character, is the only position which gives human reason a field for successful operation and a method of true progress in knowledge.
~ Cornelius Van Til (The Defense of the Faith,124-25)