This is from Berkhof’s Introduction to Systematic Theology.
The Word of God presupposes the darkness and error of the natural man, and would therefore contradict itself, if it submitted itself to the judgment of that man. It would thereby acknowledge one as judge whom it had first disqualified (p. 172).
In other words, reason cannot prove the trustworthiness of Scripture. This is because reason only comes packaged in damaged goods. Even the regenerate person still has sin clinging to his reason. How could any untrustworthy instrument prove perfection to be correct? To do that, we would ourselves have to be more foundational than the Bible. No, the Bible is our axiom.