Here's another question: does decadence exist? The physicist would say that it's a meaningless question; the historian -- or politician -- would be well advised not to listen.

(Barzun, in From Dawn to Decadence, defined a decadent period as one which has an objective which it wants to reach, which it could reach if it made the sort of changes which it has made in the past, and which it fails to reach nonetheless. I forget where I heard it, but there's an idea that there's social technology as well as physical -- and social technology is easier to lose.)