As long as new ideas can breed in this way, then human economic progress can continue. It may be only a year or two till world growth resumes after the current crisis, or it may for some countries be a lost decade. It may even be that parts of the world will be convulsed by a descent into autarky, authoritarianism and violence, as happened in the 1930s, and that a depression will cause a great war. But so long as somewhere somebody is incentivised to invent ways of serving others’ needs better, then the rational optimist must conclude that the betterment of human lives will eventually resume.