FROM the time human beings started to reflect on their condition until the fourth or fifth decade of the present century, the essence of human nature was ferociously debated.  Answers varied from the Platonic tri-partition of the soul to the Christian idea of original sin to Rousseauian goodness.  However, the social sciences, which flourished in the United States after World War II, treated human nature as they did national character—as a subject best left unaddressed primarily for political reasons. Man was what we made of him, and culture replaced nature as the first cause of social life. Although the aims of social science were ambitious, the theorizing was modest. Rather than large truths about the human condition, investigators sought “middle range” theories that could be subject to empirical verification. In more recent years, a post-modern skepticism has come to distrust the social-science project, but it has not questioned its lack of interest in human nature. Indeed, contemporary statements about the social construction of human “nature” leave nothing outside artificially created realities.