Whether that is valid to the Hindu or the Athenian rests on the validity of their logic and the following of a sound epistemology as they see it. If it is indeed concordant with reality under their interpretation, then it is properly understood and valid. When it comes to my claim of the existence of such a true interpretation in accordance with my understanding of things, however, those religions are not for me to analyze. I know almost nothing about them in comparison to Christianity. I am also a Daoist of sorts, that being also the only other one that I understand somewhat well, and I think it is sound when properly understood.