Lon L. Fuller

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Lon L. Fuller
Born (1902-06-15)June 15, 1902
Hereford, Texas, United States
Died April 8, 1978(1978-04-08) (aged 75)
Munich, Bavaria, Germany
Era 20th-century philosophy
Region Western Philosophy
Main interests
Legal philosophy
Notable ideas
“Eight Ways to Fail to Make a Law,” "The Demands of the Inner Morality of the Law," Eight Legal Excellences"

Lon Luvois Fuller (June 15, 1902 – April 8, 1978) was a noted legal philosopher, who criticized legal positivism and defended a secular and procedural form of natural law theory. Fuller was professor of Law at Harvard University for many years, and is noted in American law for his contributions to both jurisprudence and the law of contracts. His debate in 1958 with the prominent British legal philosopher H. L. A. Hart in the Harvard Law Review (Vol. 71) was important in framing the modern conflict between legal positivism and natural law theory. In his widely discussed 1964 book, The Morality of Law, Fuller argues that all systems of law contain an "internal morality" that imposes on individuals a presumptive obligation of obedience. According to law professor Robert S. Summers, "Fuller was one of the four most important American legal theorists of the last hundred years."[1]

The Internal Morality of Law

In his 1958 debate with Hart and more fully in The Morality of Law (1964), Fuller sought to steer a middle course between traditional natural law theory and legal positivism. Like most legal academics of his day, Fuller rejected traditional religious forms of natural law theory, which view human law as rooted in a rationally knowable and universally binding "higher law" that derives from God.[2] He also rejected the idea, found in some traditional natural law theorists and famously endorsed by Martin Luther King, Jr. in his Letter from Birmingham Jail, that an unjust law is not a law. On the other hand, Fuller also denied the core claim of legal positivism that there is no necessary connection between law and morality. According to Fuller, certain moral standards, which he calls "principles of legality," are built into the very concept of law, so that nothing counts as genuine law that fails to meet these standards. In virtue of these principles of legality, there is an inner morality to the law that imposes a prima facie moral obligation to obey any particular law. Some laws, he admits, may be so wicked or unjust that they should not be obeyed. But even in these cases, he argues, there are positive features of the law that impose a defeasible moral duty to obey them.

According to Fuller, all purported legal rules must meet eight minimal conditions in order to count as genuine laws. The rules must be (1) sufficiently general, (2) publicly promulgated, (3) prospective (i.e., applicable only to future behavior, not past), (4) at least minimally clear and intelligible, (5) free of contradictions, (6) relatively constant, so that they don't continuously change from day to day, (7) possible to obey, and (8) administered in a way that does not wildly diverge from their obvious or apparent meaning.[3] These are Fuller's "principles of legality." Together, he argues, they guarantee that all law will embody certain moral standards of respect, fairness, and predictability that constitute important aspects of the rule of law.

Fuller presents these issues in The Morality of Law with an entertaining story about an imaginary king named Rex who attempts to rule but finds he is unable to do so in any meaningful way when any of these conditions are not met. Fuller contends that the purpose of law is to subject "human conduct to the governance of rules".[4] If any of the eight principles is flagrantly lacking in a system of governance, the system will not be a legal one. The more closely a system is able to adhere to them, the nearer it will be to the rule-of-law ideal, though in reality all systems must make compromises and will fall short of perfect ideals of clarity, consistency, stability, and so forth.

In a review of The Morality of Law, Hart criticises Fuller's work, saying that these principles are merely ones of means-ends efficiency; it is inappropriate, he says, to call them a morality.[5] Employing Fuller's eight principles of legality, one could just as well have an inner morality of poisoning as an inner morality of law, which Hart claims is absurd. Other critics have challenged Fuller's claim that there is a prima facie obligation to obey all laws. Some laws, it is claimed, are so unjust and oppressive that there is not even a presumptive moral duty to obey them.[6]


  • Law in Quest of Itself, 1940
  • Basic Contract Law, 1947 (second edition, 1964)
  • Problems of Jurisprudence, 1949
  • The Morality of Law, 1964 (second edition, 1969)
  • Legal Fictions, 1967
  • Anatomy of Law, 1968

See also


  1. Summers, Robert S., Lon L. Fuller. London: Edward Arnold, 1984, p. 1. (The other three, according to Summers, are Oliver Wendell Holmes, Jr., Roscoe Pound, and Karl Llewellyn.)
  2. Summers, Lon L. Fuller, p. 64.
  3. Lon L. Fuller, The Morality of Law, rev. ed. New Haven CT: Yale University Press, 1969, pp. 33-38; cf. Summers, Lon L. Fuller, p. 28.
  4. Fuller, The Morality of Law, p. 74.
  5. H. L. A. Hart, Essays in Jurisprudence and Philosophy. Clarendon Press, Oxford, 1983, p. 347.
  6. Andrew Altman. Arguing about Law: An Introduction to Legal Philosophy, 2nd ed. Belmont, CA: Wadsworth, 2001, p. 57.

Further reading

External links