Original sin. Once Adam bit the apple, he suddenly "knew" that he was naked.
Self-awareness is one of the "singularities" in the evolution of the Universe -- specifically in humans ... that Godwin talks about in "One Cosmos, Under God".
Reminds me of a limerick Alan Watts introduced to me:
"There once was a man who said though,Don't mean to go all deep on y'all here. Just readin' some stuff to help expand my de-mental-tion.
It seems that I know that I know,
What I'd like to see,
Is the I that knows me,
When I know that I know that I know."
Dang, Bob. Yer word plays 'r gettin' to me.