Cornelius Van Til (1895-1987) was the Dutch-American Reformed theologian who taught apologetics at Westminster Theological Seminary in Philadelphia for forty-three years (1929-1972). He developed presuppositional apologetics, arguing that no neutral common ground exists between believer and unbeliever — both interpret all data from prior philosophical commitments — and that the Christian apologist must therefore expose the impossibility of the contrary by showing how non-Christian worldviews cannot account for logic, science, ethics, or meaning on their own terms. Major works: The Defense of the Faith, A Christian Theory of Knowledge, Christian Apologetics. His method was popularized after his death by Greg Bahnsen and John Frame, and continues to shape Reformed engagement with secularism.