One hundred years ago, Roscoe Pound wrote his famous article, “Law in Books and Law in Action.” Considered an important step toward American legal realism, today this article is invoked more for its title than its content. I would argue that in the article, Pound did not clearly distinguish between two separate situations: (1) the departure of decisions of courts from statements of statutory (or constitutional) law, and (2) the discrepancy between doctrine in books and empirical data about law. This second observation has fed various strands of jurisprudence, if often only through the repetition of the well-quoted formula. It is not my purpose here to address all of the controversies concerning the relationship between legal science and fac...