Imagine you’re on a quest to understand the very nature of computation. You’re deep in the wilderness, far from any paths, and inscrutable messages are carved into the trunks of trees all around you — BPP, AC0, Σ2P, YACC, and hundreds of others. The glyphs are trying to tell you something, but where to begin? You can’t even keep them all straight. Few researchers have done as much as Russell...