Subject for debate?
God is not subject for debate, because he is who he is and what he is. We are told that the unbeliever, of course, does not agree with that; and that is perfectly true; but that makes no difference. We believe it, and it is a part of our very case to assert it. Holding the view that we do, believing what we do about God, we cannot in any circumstances allow him to become a subject for discussion or a debate or investigation.
— Martyn Lloyd-Jones, Preaching and Preachers, page 58
I do certainly admire Lloyd-Jones, and his text on preaching is my go-to. But I would clarify a matter here. Romans 1 affirms that everyone knows that God exists, and those who deny his existence suppress the truth. The unbeliever might diligently argue against God’s existence, but he knows that his argument is not valid.