Reason is a crypto-theistic Mind-God. And there's no argument for it or against it that does not commit the core fallacy of assuming it in order to question it or argue for it. As the slogan of this blog says, the belief-deciding authority of Reason is already God-level. And any argument against that claim necessarily assumes it.
As atheist Brand Blanshard said on the first page of his 2-volume The Nature of Thought, truth is that which fits into an already necessarily-assumed system of cognition that tests for it. But only a mind processes truth claims. The problem is that if reason is inert and unaffectable by circumstance or change of environment (much like the monolith in 2001: A Space Odyssey), then it transcends the empirical world and is indistinguishable from the underlying Logos of the universe, common to the Greeks and the New Testament usage of the term. As the Gospel of John says, "In the beginning was the Logos, and the Logos was with God, and the Logos *was* God."
