There is history the way Tolstoy imagined it, as a great, slow-moving weather system in which even tsars and generals are just leaves before the storm. And there is history the way Hollywood imagines it, as a single story line in which the right move by the tsar or the wrong move by the general changes everything. Most of us, deep down, are probably Hollywood people. We like to invent what if scenarios--what if x had never happened, what if y had happened instead?--because we like to believe that individual decisions make a difference: that, if not for x, or if only there had been y, history might have plunged forever down a completely different path. Since we are agents, we have an interest in the efficacy of agency.