The trouble is that I often don't know what a "useful fact" is even after I've learned it. I certainly don't expect to be able to figure that out before I've l

The trouble is that I often don't know what a "useful fact" is even after I've learned it. I certainly don't expect to be able to figure that out before I've learned it! A segment I once saw on Reading Rainbow (airdate: 1986) recently changed my life. Trivial factoid for 2 decades, then boom, useful data point. Nobody could have predicted the set of experiences I'd have that would create a context in which this was useful. When my dad was in college, a classmate of his complained that he'd never need something taught in a particular course. The professor's response was "The only way to be sure of that is to take the course!" (If you still think it was worthless on your deathbed, I'll give you a refund...) If you can figure out a priori what's going to be important without knowing it, I'd like to see your stock portfolio. :-)