Prior to the publication of Hart's The Concept of Law, it was not uncommon for legal philosophers to identify jurisprudence with the quest for a definition of “law.”The subject of this paper is “law” as it pertains to systems of governance of human conduct. Therefore we are not offering an analysis of “law” as it pertains to regularities in nature and thus we do not explore the semantic or metasemantic relations between the two.See, for example, Herman Kantorowicz, THE DEFINITION OF LAW (Cambridge University Press, 1958). In a similar vein, see Lewis Zerby's suggestion that “the most famous definition of law [sic]… is that made by Justice Holmes when he said: ‘The prophecies of what courts will do in fact, and nothing more pretentious, are what I mean by law.‘” Some Remarks on the Philosophy of Law, 46 J. PHIL. 773–779 (1949). Hart explicitly resisted this characterization of the ambition of jurisprudence; the subject matter of jurisprudence is law, not “law.” Notwithstanding Hart's assertions to the contrary, in Law's Empire Ronald Dworkin argues that Hart's own legal positivism as well as other familiar jurisprudential theories (like natural law) are semantic theories: that is, accounts of the meaning of “law.” Dworkin further identifies semantic theories with criterialism, according to which the meaning of a term is given by shared criteria for applying it. The meaning of the expression “law” on this view is given by a rule or set of criteria specifying the conditions that must be satisfied in order properly to employ that expression, and the project of a semantic jurisprudence is to identify that rule.

No one denies that moral principles figure in legal argument and practice. However, the kind of role morality can or must play in law has been a topic of debate not only between positivists and their critics, but also within the positivist camp. The topic was brought into contemporary prominence by Ronald Dworkin, who in The Model of Rules I made the provocative observation that the legality of norms appears to depend sometimes on their substantive (moral) merits, and not just on their pedigree or social source.Ronald Dworkin, The Model of Rules I, in TAKING RIGHTS SERIOUSLY 14 (1977). The observation was intended by Dworkin as a challenge to the positivism of H.L.A. Hart.

H.L.A. Hart's The Concept of Law is the most important and influential book in the legal positivist tradition. Though its importance is undisputed, there is a good deal less consensus regarding its core commitments, both methodological and substantive. With the exception of an occasional essay, Hart neither further developed nor revised his position beyond the argument of the book. The burden of shaping the prevailing understanding of his views, therefore, has fallen to others: notably, Joseph Raz among positivists, and Ronald Dworkin among positivism's critics. Dworkin, in particular, has framed, then reframed, the conventional understanding, not only of Hart's positivism, but of the terms of the debate between positivists and him. While standing on the sidelines, Hart witnessed the unfolding of not only a lively debate between positivists and Dworkin, but an equally intense one among positivists as to positivism's (and his) core claims. The most important debate has been between so-called inclusive and exclusive positivists: a debate as much about Hart's legacy as about the proper interpretation of legal positivism.

There is a close but largely unexplored connection between law and economics and cognitive psychology. Law and economics applies economic models, modes of analysis, and argument to legal problems. Economic theory can be applied to legal problems for predictive, explanatory, or evaluative purposes. In explaining or assessing human action, economic theory presupposes a largely unarticulated account of rational, intentional action. Philosophers typically analyze intentional action in terms of desires and beliefs. I intend to perform some action because I believe that it will (is likely to) produce an outcome that I desire. This standard “belief-desire” model of action invokes what philosophers of psychology and action theorists aptly refer to as a “folk psychology.”

Suppose the prevailing distribution of property rights is unjust as determined by the relevant conception of distributive justice. You have far more than you should have under that theory and I have far less. Then I defraud you and in doing so reallocate resources so that our holdings ex post more closely approximate what distributive justice requires. Do I have a duty to return the property to you?

There are many good reasons for requiring me to return to you what I have taken. One is that while you may have no right in justice to all that you own, it does not follow that I do, or that I have a right to take it. Thus, requiring me to return the property to you is a way of recognizing that I had no right to take it from you in the first place.

This essay is part of a larger project exploring the extent to which the market paradigm might be usefully employed to explain and in some instances justify nonmarket institutions. The focus of the market paradigm in this essay is the relationship between the idea of a perfectly competitive market and aspects of both the rationality of political association and the theory of collective choice. In particular, this essay seeks to identify what connections, if any, exist between one kind of market account of the rationality of political association and one kind of market-based social choice rule. The market theory of political association I intend to discuss I call “market contractarianism,” and the collective choice rule whose relation to it I intend to explore is the unanimity rule. What, if anything, is the relationship between market contractarianism and the unanimity rule?