> The fundamental distinction is between knowledge that compounds and knowledge that decays.

I don't agree with this at all. I don't think there's any such thing as "knowledge that decays" in this sense, and all knowledge compounds. I think that everything is worth learning and knowing.

But, to address the basis of the essay, in a world where I can't learn and know everything, how do I decide what to learn and know? For me, it's really, really easy. If I'm interested in it, then it's worth learning. It's just that simple and has yet to steer me wrong.