Cornelius Van Til (1895-1987), Reformed theologian and apologist, was born in the Netherlands and completed his Ph.D. at Princeton University in 1927. He taught apologetics for one year at Princeton Theological Seminary but left when the board voted for a reorganization to allow for liberal viewpoints. Van Til and other conservative professors who left Princeton founded Westminster Theological Seminary in Philadelphia. Van Til taught at Westminster from its beginning in 1929 for roughly a half century.
Van Tit's studies of philosophical idealism convinced him that all human thought is governed by presuppositions. (Hence Van Til is sometimes called a "presuppositionalist," though he was not enthusiastic about that label.) Ultimate presuppositions, he believed, cannot be proved by usual methods, since they serve as the basis of all proof. But they can be proved "transcendentally," by showing that they are necessary for all rational thought and must be true if there is to be any meaning or order in the world. Van Tit sought to reconstruct Christian apologetics so that it would establish the Christian God as the presupposition of human thought, rather than as one rational conclusion among many.
He disparaged the "traditional method" of defending Christianity by theistic proofs and historical evidences, because he believed that tradition began with data considered intelligible apart from God and thereby tried to prove God's existence. On the contrary, Van Til argued, if we concede that anything is intelligible apart from the God of Scripture, we have lost the battle at the outset. So we should, rather, use a transcendental method, showing that the various forms of non-Christian thought ("would-be autonomous reasoning," as he put it) reduce to meaninglessness and that only the Christian worldview can make sense of anything.
Some critics said that Van Til left no room for the use of evidence in apologetics. He replied that evidence is useful when employed within a transcendental argument based on biblical presuppositions.
But is this not circular, to prove Christianity on the basis of Christian presuppositions?
Yes, said Van Til, in a sense. But he offered two arguments in defense of his view. First, every system of thought is circular when arguing its most fundamental presuppositions (e.g., a rationalist can defend the authority of reason only by using reason). Second, the Christian circle is the only one that renders reality intelligible on its own terms.
Non-Christian thought, he argues, collapses into meaninglessness because of the effects of sin on human mental powers. The unbeliever knows God but suppresses the truth (Rm L18-32). There is therefore an antithesis between Christian thought and unbelieving thought, between the wisdom of God and the wisdom of the world. Although the unbeliever knows and states truth occasionally, he does that only by inconsistency with his presuppositions and by relying inconsistently on the Christian worldview.
Extracted from the Apologetics Study Bible.