The future of work depends on two forces: a harmful substituting force and a helpful complementing one. Many tales have a hero and a villain fighting each other for dominance, but in our story, technology plays both roles at once, displacing workers while simultaneously raising the demand for their efforts elsewhere in the economy. This interaction helps explain why past worries about automation were misplaced: our ancestors had predicted the wrong winner in that fight, underestimating quite how powerful the complementing force would prove to be or simply ignoring that factor altogether. It also helps to explain why economists have traditionally been dismissive of the idea of technological unemployment: there appeared to be firm limits to the substituting force, leaving lots of tasks that could not be performed by machines, and a growing demand for human beings to do them instead.