"We spend a lot of time and effort trying to figure out who's going to be a good NFL quarterback, and we do a very bad job of it. We don't really know. And we also spend a lot of time trying to figure out who will be a good teacher, and we're really bad at that too. We don't know if someone is going to be a good teacher when they start teaching. So what should we do in those situations in which predictions are useless?"