Will the world be better off with fewer people? For years that has been a hypothetical question, posed to suggest an affirmative answer. Fewer people, it was claimed, would mean less depredation of natural resources, less urban overcrowding, more room for other species to stretch their (actual or metaphorical) legs. Mankind was a parasite, a blight, and overpopulation a disease. Fewer people would mean a better Earth.

Not everyone has agreed. More people, argued the late economist Julian Simon, means more inventors, more innovators, more creators. Benjamin Franklin was the 15th of his father’s 17 children. Would America, and the world, have been better off if the man had stopped at 14?