Bryan Kaplan poses an intriguing theory
Religious architecture and art were to medieval feudalism what advertising and commercialism are to modern capitalism: A rather effective way to build support for the status quo using aesthetics instead of argument. My claim, in short, is that Notre Dame played the same role during the Middle Ages that fashion magazines play today. Notre Dame was not an argument for feudalism, and Elle is not an argument for capitalism. But both are powerful ways to make regular people buy into the system.
Follow the link and you get a better picture of his idea:
Less than a decade ago, I drove from former West Germany to former East Germany, and was struck by how much more beautiful the West was. Houses in the West had flower boxes. Houses in the East did not. I reflected that the aesthetic gap between West and East used to be vastly greater. And I recalled how people I knew who toured the Soviet bloc were more likely to sadly describe the "greyness" of communist life than the machine guns at the border.
The upshot is that the private pursuit of beauty in the West had a striking externality. Every time a West German put a flower box in his window, he was making capitalism look prettier than socialism. And while intellectuals may say they couldn't care less about such things, I suspect that sheer aesthetics changed a lot of minds about East versus West.
(Link via Sully)
Update: The Notre Dame example is off the mark. Pretty cathedrals do positive PR for Christianity, not feudalism. Although during the time of a cathedral's construction feudalism might get some negative PR among the serfs forced to pay the bill.