What is “law”? In a forthcoming essay, Brian Leiter provides an excellent summary of H.L.A. Hart’s influential legal positivist theory of law. (The cover of his classic tome, “The Concept of Law”, is pictured below.) In particular, Professor Leiter, who teaches legal philosophy at the University of Chicago, claims that Hart’s account of legal positivism has three advantages over competing theories: (1) Hart’s theory provides a common sense or plausible account of the ordinary man’s understanding of law, (2) it can be tested empirically, and (3) it is parsimonious. Let’s examine each of these claims in turn:
First and foremost, if we are looking for a theory that best captures the ordinary man’s understanding of law, we need look no further than Oliver Wendell Holmes’s famous but now unfashionable bad man theory of law, which Holmes enunciated in his classic work “The Path of the Law,” published in 1897. Hart’s theory of legal positivism, by contrast, requires us to posit a quasi-mystical entity: the so-called “internal point of view.” Since so many others have covered this well-worn theoretical ground before, suffice it to say the internal point of view is quasi-mystical because it requires us to figure out what is going on within the inner recesses of the minds of certain legal officials.
Secondly, unless we are prepared to dispense with the internal point of view, Hart’s legal positivist theory of law is not empirically testable in any meaningful or Popperian sense. Unlike Holmes’s bad man theory of law, which can be tested (since we can, in principle, measure rates of legal compliance and evasion), Hart’s theory requires us to survey the multifarious and possibly contradictory motives of certain persons for accepting the legal system. More skeptically, we could also argue that the many competing theories of law are just aesthetic world-views or theoretical “paradigms” (to borrow from Thomas Kuhn’s influential theory of scientific revolutions), ways of looking at the law tout court. On this Kuhnian view of legal theory, no amount of evidence or research will persuade one to change one’s world view, even if you’re a Bayesian.
Lastly, legal positivism is not as parsimonious as legal positivists would have us believe. According to Professor Leiter, for example, Hart’s own theory is premised on two separate ideas, what Leiter labels the Sources Thesis (or in the words of Leiter, the idea that “norms are legally valid only in virtue of having certain sources … without regard for their merits”) and the Conventionality Thesis (the idea that “the relevant sources of law in each society are fixed by a contingent practice of officials of the legal system”). Other legal theorists, like Richard Holton, claim that legal positivism is premised on three separate theses, not two. Whatever the case, my point here is not to rehash the central tenets of legal positivism. My point is simply that legal positivism is not so parsimonious at all once one delves into the intricate details of Hart’s theory. (Again, if it’s parsimony we’re after, Holmes’s bad man theory of law provides the most parsimonious explanation of law.)