Some people mischaracterize the approach by saying that presuppositionalists claim that unbelievers have a problem with knowledge – that unbelievers can never justify their beliefs. This is not correct. God has revealed Himself to everyone. So unbelievers can indeed have knowledge. And their knowledge is justified in exactly the same way as the believer’s knowledge – by revelation from God. The Bible is true whether the unbeliever will profess it or not.

The problem with the unbeliever is not that he cannot justify any of his beliefs. Rather, the problem is that he cannot justify any of his beliefs within his professed worldview. If evolution were true, then knowledge would be impossible. But evolution is not true. Since the Bible is true, evolutionists are able to have knowledge. Their beliefs in sensory experience and rationality are ultimately justified because the Bible is true.

Consequently, the fact that unbelievers do have knowledge demonstrates the truth of Christian worldview. Furthermore, it shows that they do know God. Apart from the biblical God, it would make no sense to trust in sensory experience or the rationality of the mind. When unbelievers accept these truths, it exposes their suppressed knowledge of God in a spectacular confirmation of Romans 1:18-25.

So, the proof of the Bible isn’t a vicious circle such as “The Bible is God’s Word because it says it is.” Rather, the proof is that the Bible says it is God’s Word and makes knowledge possible. This is something the Bible itself indicates (Proverbs 1:7, Colossians 2:3). The Bible proves itself and is the only basis for proving anything else. It’s not a simple (vicious) circle, but a spiral that goes beyond itself and justifies our other beliefs. The proof of the Bible is the impossibility of the contrary. If the Bible were not true, we couldn’t prove that anything is true.