According to Wayne Grudem, apologetics is “the discipline that seeks to provide a defense of the truthfulness of the Christian faith for the purpose of convincing unbelievers.”

Dr. Greg Bahnsen was an excellent apologist.

Within Christendom, there are at least three distinct philosophies that answer the “how” and “why” of Christian apologetics. These three major apologetic philosophies have titles: 1. Classical Apologetics, 2. Evidential Apologetics, and 3. PresuppositionalApologetics.

Dr. Greg Bahnsen was an excellent presuppositional apologist.

As a presuppositionalist, Dr. Bahnsen argued for the existence of the Christian God based on the lunacy of believing anything else. He pleaded for lost people to consider their own worldviews. He challenged them to honestly evaluate and defend their epistemology (the nature of knowledge itself).

Dr. Bahnsen was extremely biased in his conclusions because He looked at all of life through certain Christian presuppositions. He presupposed that God exists. He presupposed that the Bible was this God’s Word. He presupposed that a man without God is blinded to the truth (Romans 1). And he freely admitted that he was biased! But everyone else is biased too — and proving that was his specialty. He made his opponents squirm under the unavoidable and uncomfortable truth that they too held certain presuppositions, and that their presuppositions just didn’t cut the mustard. A person without presuppositions is like a computer without software. Without software the computer does not, yea, cannot function. But as most of us know all too well, some software is good (it works) and some is bad (it crashes your system). Some presuppositions are downright dangerous. Some will forever blind a soul from truth and condemn a man to hell.

The lost world says: “I’ll believe it when I see it!” Jesus says: “Believe it and you shall truly see! (John 11:40)”

C.S. Lewis, not known for his presuppositional bent, obviously grasped the essence of presuppositional apologetics when he said: “I believe in Christianity as I believe that the sun has risen: not only because I see it, but because by it I see everything else.” All of us see the world through certain presuppositions, or preconceived notions, or basic worldviews, or most-fundamentally-held-beliefs. We can think of presuppositions as the colored lenses of the sunglasses of our mind. We see everything through those sunglasses, and all that we see is colored by our presuppositions.

A humorous example of how important presuppositions are when interpreting facts is the frog scientist. The scientist takes a frog, puts it on a line, and says “Jump!” The frog jumps 10 feet. This fact he notates in his journal. The scientist now cuts one of the frogs legs off. He repeats the process . . . “Jump!” The frog jumps 4 feet. The scientist records“When frog has 3 legs, frog jumps 4 feet.” The scientist cuts off another leg. This time the frog jumps 2 feet. The scientist notes this as well, then he chops off the remaining two feet and sets it back on the line. “Jump! . . . Jump! . . . JUMP!!!” The frog does nothing. The scientist’s conclusion? “When all four legs are removed from frog, frog becomes deaf.” The scientist had the same facts, or reality, as any other scientist might in an experiment such as that, but his conclusion was greatly skewed because of faulty presuppositions.

Let’s get real practical: you presuppose that someone wrote these words that you’re reading right now. This blog post did not happen without a human typing words in a somewhat thoughtful, meaningful pattern with specific intent. But what if, just for a moment, you did not have that presupposition about the words you’re reading? Are there any other presuppositions besides that one that you could cling to that would make sense in explaining this post? This is the heart of the presuppositionalist’s defense of Christianity: demonstrating that no other presuppositions make sense out of life like the Christian’s presuppositions and that ALL opposing presuppositions are ludicrous when wholly examined.

Dr. Bahnsen did not present evidence and ask for a conclusion; rather, he inquired as to how a lost person could trust any conclusion based on no absolutely authoritative presuppositions. And when he began to peel away the attractive cover of the lost world’s presuppositions, he didn’t just dismantle them — he obliterated them. Dr. Bahnsen was often introduced as “the man atheists fear most.”

But does God need defending from the atheists? No. Not really. God is God. Forget about obliterating worldviews, God can obliterate atheists. God certainly doesn’t need defending in a way that robs Him of glory. Some branches of apologetics rely upon man’s grasp of reality and man’s ability to reason to come to a good, life-saving, life-changing decision. But if one’s trust is in man’s reason, then one’s trust is sadly misplaced. Sinful man is a lost, blind, dead, enemy against any and all Christian presuppositions.

A presuppositionalist recognizes that sinful man is dead in sin (Ephesians 2:1–5) and blinded to the truth (2 Corinthians 4:4). The presuppositionalist understands that no amount of evidence or logic will convince an unbeliever of the truth since the unbeliever views the evidence and logic presented through entirely differnent colored lenses than the believer! There needs to be a changing of sunglasses! The unbeliever will not awaken without God’s grace. And what is God’s divine method for casting down our natural presuppositions and imparting His Own? His Word. James 1:18.

So presuppositionalists aim their canons at the most basic premises and foundations of the lost man’s grasp of reality and assumed ability to reason. Bahnsen taught that there is no reality or true ability to reason without holding Christian presuppositions. Bahnsen argued that the atheist must “borrow” certain presuppositions from the Christian worldview in order to make any kind of sense at all! This becomes a great platform then for teaching the truth of God’s Word and bombarding the hearer with absolute, objective, God-given, Christian presuppositions.

Consider: Does your defense of Christianity bring glory to God? Do your efforts to convince unbelievers of the truth bring glory to God? I’m not talking about your eloquence, your winsome charisma, or your four points and a poem— I’m talking about your foundational beliefs about where/how/what the one without God really is. I believe the presuppositional defense of the faith brings glory to God because it brings people back to the authority and sufficiency of the Word.

Greg Bahnsen’s doctoral work on self-deception may be found HERE

Disclaimer: Please read Bahnsen with a Baptist grain of salt -- especially his eschatlogical views. Thank you.