The first was the Enlightenment. Hobbes claimed the brutishishness of man in a state of nature called for a governmental Leviathan. Rousseau's concept of the noble savage led him to call for the abolition of property and the predominance of the "general will." Adam Smith justified market capitalism by saying that it is not the generosity but the self-interest of the baker that leads him to give us bread. Madison justified constitutional government by saying that if people were angels, no government would be necessary, and if angels were to govern people, no controls on government would be necessary. The young Marx's notion of a "species character" for creativity and self-expression led to "From each according to his ability"; his later belief that human nature is transformed throughout history justified revolutionary social change.
The second period was the 1960s and its immediate aftermath, when Enlightenment romanticism was revived. Here is an argument the US Attorney General, Ramsay Clark, against criminal punishment: "Healthy, rational people will not injure others ... they will understand that the individual and his society are best served by conduct that does not inflict injury. ... Rehabilitated, an individual will not have the capacity-cannot bring himself-to injure another or take or destroy property." This is, of course, an empirical claim about human nature, with significant consequences for policy.
The discussion came to an end in the 1970s, when even the mildest non romantic statements about human nature were met with angry denunciations and accusations of Nazism. At the century's turn we have an unprecedented wealth of data from social psychology, ethnography, behavioral economics, criminology, behavioral genetics, cognitive neuroscience, and so on, that could inform (though of course, not dictate) policies in law, political decision-making, welfare, and so on. But they are seldom brought to bear on the issues. In part this is a good thing, because academics have been known to shoot off their mouths with half-baked or crackpot policy proposals. But since all policy decisions presuppose some hypothesis about human nature, wouldn't it make sense to bring the presuppositions into the open so they can be scrutinized in the light of our best data?
STEVEN PINKER is professor in the Department of Brain and Cognitive Sciences at MIT; director of the McDonnell-Pew Center for Cognitive Neuroscience at MIT; author of Language Learnability and Language Development, Learnability and Cognition, The Language Instinct , How the Mind Works, and Words and Rules.