The case for racial preferences in higher education has long been made using sophistry designed to hide the heavy social and moral costs of affirmative action. In “For Discrimination: Race, Affirmative Action, and the Law,” Randall Kennedy makes that case with rare intellectual honesty and fair-mindedness. And while it won’t persuade opponents of the policy, the book has the salutary effect of clarifying the terms of the debate.

The author, a professor at Harvard Law School, begins building his case for racially…