Do Christians or atheists have the burden of proof? This is what Gordon Clark writes on the subject. These excerpts come from the article Atheism at the Trinity Foundation.
The Atheist Challenge
“But atheists, like agnostics, shift the burden of proof and say the theist is under obligation to demonstrate the truth of his view; but the atheist considers himself under no such obligation.”
“Every system of theology or philosophy must have a starting point. Logical Positivists started with the unproved assumption that a sentence can have no meaning unless it can be tested by sensation. To speak without referring to something that can be touched, seen, smelled, and especially measured, is to speak nonsense. But they never deduce this principle. It is their non-demonstrable axiom. Worse, it is self-contradictory, for it has not been seen, smelled, or measured; therefore it is self-condemned as nonsense.
If the axioms of other secularists are not nonsense, they are nonetheless axioms. Every system must start somewhere, and it cannot have started before it starts. A naturalist might amend the Logical Positivist’s principle and make it say that all knowledge is derived from sensation. This is not nonsense, but it is still an empirically unverifiable axiom. If it is not self-contradictory, it is at least without empirical justification. Other arguments against empiricism need not be given here: The point is that no system can deduce its axioms.
The inference is this: No one can consistently object to Christianity’s being based on a non-demonstrable axiom. If the secularists exercise their privilege of basing their theorems on axioms, then so can Christians. If the former refuse to accept our axioms, then they can have no logical objection to our rejecting theirs. Accordingly, we reject the very basis of atheism, Logical Positivism, and, in general, empiricism. Our axiom shall be, God has spoken. More completely, God has spoken in the Bible. More precisely, what the Bible says, God has spoken.”