From an interview in 2006 (video below):
I have a message for future generations. That is please accept our apologies.. we were roaring drunk on petroleum. Everything that distinguishes our era from the dark ages is what we've been able to do with petroleum … and that is going to end very soon. I think in the next few years we're going to see the price of fossil fuels go through the roof, and there will be no substitutes for gasoline. I think that, from my reading of history, the only fun most human beings have ever had - any feeling of power and respect - has been driving automobiles, you get in a car and everyone respects you; and people aren't going to give that up easily.