Circular reasoning

Then that should rule out your use of the Bible as an authority. When did you become an atheist? Not so. They may say that. But they are really declaring their favored theologians as the authority. If it were as easy as making God the authority, and settling issues by asking God and getting an answer, then we would not have so many disagreements between different Christian denominations and sects. I don't think that's correct. I think they point to reason and evidence, not to reason alone.I'm not sure why you don't see it, but pointing to reason and evidence as the ultimate authority is just a metaphoric way of speaking. People who say that are denying that there is an ultimate authority, and are saying that they will use their own reason and evidence rather than rely on any authority. Most would look to science as a source of evidence, but not as an authority. Science itself is full of people disagreeing with one another, trying to disprove the claims of one another. That does not look at all like what one might expect of an authority. If some entity declares itself the ultimate authority, you should run away as fast as you can. For, surely that entity is evil.I still cannot understand why you think your OP is about circular reasoning.

In that case, I will make my cat the ultimate authority - just as long as I get to interpret it however I want.Don't you see that playing the "interpretation" game makes a mockery of the whole idea of "ultimate authority"? Reason is a method, not an agent that one can consult. If God gave us free will, that made each of us our own ultimate authority.