Learn by working on hard problems

From Paul Graham’s “Undergraduation” (March 2005):

Thomas Huxley said “Try to learn something about everything and everything about something.” Most universities aim at this ideal.

But what’s everything? To me it means, all that people learn in the course of working honestly on hard problems. …

Working on hard problems is not, by itself, enough. Medieval alchemists were working on a hard problem, but their approach was so bogus that there was little to learn from studying it, except possibly about people’s ability to delude themselves.