Greg Bahnsen was an American theologian and philosopher known for his work in the field of presuppositional apologetics. He was a prominent figure in the Reformed tradition and is best known for his defense of the Christian faith against secular philosophies. Bahnsen emphasized the importance of a biblical worldview and argued that all reasoning must be grounded in the existence of God. In addition to his apologetic work, Bahnsen was also a prolific writer and speaker. He authored several books, including "Van Til's Apologetic," which explores the ideas of his mentor, Cornelius Van Til. Bahnsen's influence continues to be felt in contemporary discussions on faith, reason, and the relationship between Christianity and philosophy.