Autonomous Presuppositions?

Question
I am in an internet discussion on an atheist forum. In trying to make a challenge to the atheistic position, i.e., that autonomous thought does not provide a foundation for any knowledge and cannot make sense of human experience, I have been challenged to explain how I arrived at my presupposition without exercising autonomous reason.

Basically, it comes down to this: they want me to justify my presupposition in a way that will be meaningful to them based on their atheistic presupposition and that can't be done. Somehow, though, this doesn't seem to be a sufficiently powerful answer. Is there more or can you suggest a different way of answering?
Answer
The point you made to your atheist correspondent is a sound one, but of course there is more to be said, as you surmised.

How do we arrive at our presupposition without using autonomous reason? We are aware of the need to presuppose God by means of general revelation (revelation from nature). But, as Paul says in Rom. 1, we suppress that knowledge. Nevertheless, we cannot live in the world except by the knowledge we are trying to suppress. So there is a conflict in us between the knowledge we have by God's revelation and the distortion of that knowledge through sin. This conflict can be described as a contest between rival presuppositions, neither of which the sinner espouses consistently.

Knowing the truth, even for the unbeliever, is on the basis of the godly presupposition, not the ungodly one. The ungodly one would make chaos out of any intellectual effort if it were followed consistently. So anything the unbeliever knows, he knows on the basis of divinely revealed presuppositions, not on the basis of his "autonomous reason."

Of course the unbeliever cannot come to saving faith in God through Christ from general revelation alone. Something more is needed: (1) special revelation, and (2) the witness of the Spirit creating a saving knowledge of that revelation. The witness of the Spirit makes the godly presupposition to be our dominant presupposition (though the ungodly presupposition remains a temptation to us).

So in brief: we do not come to know God through autonomous reason. We come to know God through general revelation, special revelation, and the witness of the Spirit.

On the circularity implicit here, see my Apologetics to the Glory of God and my essay in Cowan, Five Views of Apologetics.

This turns the atheist argument on its head. He says we can't have any knowledge except by presupposing our own autonomy. We say you can't have any knowledge except by presupposing God.

Certainly, every act of belief is our act of belief. But that does not imply that the act is autonomous. We often defer to authority when seeking knowledge, recognizing that another person knows more than we do. In the religious case, God is the one who deserves that kind of deference in an absolute way. Our beliefs are our beliefs, but they should always defer to his superior wisdom. That's what it means to have a godly presupposition.

Answer by Dr. John M. Frame

Dr. John M. Frame is Professor of Systematic Theology and Philosophy at Reformed Theological Seminary in Orlando, FL.