The simple model of a bridge is great, and you could not build a bridge without understanding it well. But if you're actually building the bridge, you need to know the site. A lot of economics is like that: When prices go up, demand is gonna go down. You can't forget that and run your economy. But it's not the only thing you need to know.

Maybe we could think of science as being like a nuclear chain reaction in which people and ideas bounce off each other, and if critical mass is reached, a new field is formed.

Market design is about understanding the details of markets in sufficient detail so that we can help fix them when they are broken.

I don't think I could have thought of any place other than Stanford to leave Harvard for.