If nobody can claim authority, then on what basis can anyone claim the “truth” about anything?

On what standard is your authority based?

Science? Your strength, political clout, or education?

Exploding stars – by themselves – have no ethical opinion in how or why we act a certain way.

Does that make sense?

If you think about it, this is the same for The 10 Commandments or any other reported scripture.

If it came from man – why should it be any more valid than what any other man has said?

If it came from something higher – it should have infinite value and truth.

But as we have seen, all the values which he uses in attacking the Tao, and even claims to be substituting for it, are themselves derived from the Tao. If he had really started from scratch, from right outside the human tradition of value, no jugglery could have advanced him an inch towards the conception that a man should die for the community or work for posterity. If the Tao falls, all his own conceptions of value fall with it. Not one of them can claim any authority other than that of the Tao. Only by such shreds of the Tao as he has inherited is he enabled even to attack it. The question therefore arises what title he has to select bits of it for acceptance and to reject others.

-C.S. Lewis, The Abolition Of Man (Amazon)