I don't think the source of this dialogue much matters.  I would hope and expect that many storytellers have discovered the moment independently and written it or spoken it in their own language.  But, in the spirit of keeping things free and honest, I'll reveal that this version is from Sometimes a Great Notion.  I saw it on the table just now and flipped first to page 1 and then 622 (For there is always a sanctuary more...) and then between and around and everywhere, excited that after East of Eden will come my first committed dive back into a book I've often labeled my all time favorite.

"...I still don't understand what's happening," he says after a moment.

"Maybe that's because it's still happening..."