The false self and our knowledge of it's deception proves God.

[GrandizerII]

I don't see why values must logically have a transcendent source. It's logically possible for values come from within rather than without.

Perhaps. I simply have not seem a coherent argument supporting that assertion.

You call it assertion as if your view is any better. What you call "assertion" is more a proposed explanation, one that is overall a better explanation than the God explanation. We observe that this natural world exists, and we observe that values often differ as certain human factors differ. We don't, on the other hand, observe that a divine moral lawgiver exists, and that values are constant and thereby reflect the constant nature of such a being.