I think the issue is that you are making an unprovable assertion.
That is correct, I don't deny that at all.
Now why, I ask you, do people (humanity) insist on reading the bible to discover WHO God is?
It's a starting point for those that thrist to know, no more, no less.
Our brain has a one on one relationship with the nature of our earthly reality.
Man's sin is a default of his human nature.
God's goodness is a default of God's nature.
Agree to all the above.
Communication and understanding of Man and God take place with words, writing and thoughts irrevocably tied down to an attempt at rational discourse.
Yes, that is a starting point, but I think that the written word is more about man trying to explain God to other man, than anything that God does/did, God doesn't need the written word BUT He uses it so that we can take those steps to Him.
Rational is a ratio between verifiable and non-verifiable data whereby we actually determine a DIFFERENCE!
Otherwise, morality is impossible to judge on the basis of understanding what is moral/immoral.
That's a different thread, LOL !