The Decline of Natural Law and the Rise of Exclusive Positivism

Stuart Banner’s The Decline of Natural Law: How American Lawyers Once Used Natural Law and Why They Stopped addresses a “fundamental change in American legal thought that took place in the late 19th and early 20th centuries.” Prior to this change, lawyers routinely relied on natural law in their arguments, and judges took those arguments seriously. Natural law gave judges “a reservoir of principles. . .to draw upon” in cases that positive law could not cleanly resolve, which made it easy to see judges as discovering law in those cases. After the change, however, natural law dropped out of the lawyer’s toolkit. Judges continued to rely on moral reasoning to decide hard cases, but they were now thought to be making law. Banner’s goal, as his subtitle indicates, is to explain how American lawyers once used natural law and why they stopped. The book is clearly written and a pleasure to read: Banner deftly weaves quotations from a wide variety of sources with analysis of what those sources reveal about the trajectory of natural law in the American legal system. He argues, among other things, that an explosion in the number of reported cases available to lawyers in the nineteenth century precipitated the decline of natural law. As more and more cases became available, lawyers came to rely on those cases instead of natural law and, indeed, came to view the cases themselves as sources of law rather than as evidence of what the law already was. Part I summarizes the pertinent parts of Banner’s book. Part II overviews two debates in general jurisprudence: a substantive debate between positivists and antipositivists over the relationship between law and morality and a methodological debate over how to go about resolving the first debate. Part III argues that Banner’s account of the decline of natural law helps explain an apparent shift in American lawyers’ concept of law toward an exclusive-positivist concept. I also show how acknowledging this conceptual shift gives exclusive positivists new resources for responding to common objections to their theory. Lastly, Part IV turns to the implications that Banner’s account has for the methodological debate