Cornelius Van Til (1896-1987) was a Reformed theologian, born in the Netherlands and educated at Calvin College and Seminary and Princeton Theological Seminary, who had a profound influence on many students at Westminster Seminary. Van Til defended a presuppositionalism denying that the issue between Christianity and its rivals can be decided by an appeal to agreed-upon facts. Instead he argued that every belief system is grounded in an ultimate presupposition, Christianity being grounded in the self-attesting revelation of the triune God. Non-Christian views must be critiqued by pointing out the internal contradictions that arise from their inadequate presuppositions.1
1. C.Stephen Evans, Pocket Dictionary of Apologetics & Philosophy of Religion (Downers Grove, IL: InterVarsity Press, 2002), p. 120.