Cornelius Van Til is best known for his philosophy of “presuppositionalism.” This is the belief that one’s very ability to see or understand truth comes from the presuppositional beliefs a person has. To Van Til, one must first believe in the truth of Christianity (specifically Reformed Christianity - Calvinism) and in the supernatural inerrant revelation of Scripture as the source of all truth before that person can know or understand any truth in any area of life, thought, or discovery.
This viewpoint has some troubling corollaries. As Van Til taught, because a non-Christian is fundamentally incapable of knowing truth, there is no common ground where Christians and non-Christians can agree and meet. Likewise, any “truth” arrived at by anyone who does not have the “correct” beliefs about God and the universe is suspect and unreliable, no matter what. Because that person is “totally depraved” to use the Calvinist term, he or she is incapable of seeing truth about anything without lying to him or herself about it. This is in contrast to his view of [the right sort of] Christians, who would naturally and inevitably come to superior conclusions because their theology was correct.
The topic of apologetics is beyond the scope of this post, although I hope to write about it in the future. It isn’t hard to see the influence of Van Til’s Presuppositionalism in modern Evangelical apologetics, however. It’s one area where the ideas have badly poisoned the discussion. I believe it has also poisoned the entire system of Evangelical thought.