IT is generally easier to attack someone else’s thesis than to advance your own. That lesson is borne out in Inequality by Design: Cracking The Bell Curve Myth, † a critique of Richard J. Herrnstein and Charles Murray’s study of the importance of differences in intelligence as a cause of American inequalities.  The book, written by six sociologists at the University of California, Berkeley (listed alphabetically as Claude S. Fischer, Michael Hour, Martin Sanchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Voss), begins by trying to rebut The Bell Curve’s thesis: The authors deny that intelligence differences are a central cause of inequality. They then argue their own thesis, contending that wrong-headed social policies are primarily responsible for our inequalities (and that improved social policies of a redistributionist, social-democratic sort would lessen them). In the book’s first half, the authors charge that inequality (or rather, the role of intelligence differences as its cause) is in effect “designed” by the assumptions built into Herrnstein and Murray’s research; in the second half, in which The Bell Curve receives much less attention, inequality is “designed” by the insufficiently generous social policies adopted in America.