Hart, Fuller and Devlin Theories of Law and Morality


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This essay will explore the theories of Hart, Fuller and Devlin and consider there views on the link between law and morality. It will consider the debates mounted between Hart and Fuller and Hart and Devlin and what these debates add to our understanding to the link between law and morality. It will be argued and concluded that morality plays an important and essential role in our understanding of our legal responsibilities. It will recognise that there has been a long association between morality and law and that traditionally law has been associated with religions, customs and divinity.

The Hart – Fuller Debate

To understand Hart’s criticism of Fuller it is important to familiarise and understand the eight principles of the “inner morality” of the law that Fuller asserts and how in his view law and morality are intertwined. Fuller asserts that:

A legal system must be base on or reveal some kind of regular tends. As such law should be founded on generalisations of conduct such as rules, rather than simply following arbitrary adjudication.
Laws must be publicised so that subjects know how they are supposed to behave.
Rules will not have the desired effect if it is likely that your present actions will not be judged by them in future. As such, retrospective legislation should not be abused.
Laws should be comprehensible, even if it is only lawyers who understand them
Laws should not be contradictory.
Laws should not expect the subject to perform the impossible.
Law should not change so frequently that the subject cannot orient his actions to it
There should not be a significant difference between the actual administration of the law and what the written rules say

These criteria are in the form of moral rules of duty. Fuller expresses them as principles or goals; generality of laws; promulgation of laws; minimising the use of retrospective laws; clarity; lack of contradiction; possibility of obedience, constancy through time; consistency between the words and practice of law[1].

Hart’s criticism of Fuller’s eight principles of “inner morality” of law must be understood. These principles, which loosely describe requirements of procedural justice, were claimed by Fuller to ensure that a legal system would satisfy the demand of morality, to the extent that a legal system which adhered to all of the principles would explain the all-important idea of “fidelity to law” In other words, such a legal system would command obedience with moral justification.

Fuller’s key idea is that evil aims lack a “logic” and coherence that moral aims have. Thus, paying attention to the “coherence” of the laws ensures their morality. The argument is unfortunate because it does, of course, claim too much. Hart’s criticism is that we could, equally, have eight principles of the “inner morality” of the poisoner’s art. Or we can improvise further[2]. We can talk of the principles of the inner morality of Nazism, for example, or the principles of the inner morality of chess. Fuller’s explanation of the Nazi regime is insufficient and flawed, and we must take on Hart’s analysis. Fuller argues that the Nazi regime was so intrinsically evil that it could not be law, this it is argued, is not a sufficient conclusion. The point is that the idea of principles in themselves with the attendant explanation at a general level of what is to be achieved and consistency is insufficient to establish the moral nature of such practices.

This was that there is an important sense of legal justification that claims made in the name of law are morally serious. At the least, the person who makes a genuine claim for legal justification of an immoral, Nazi-type legal system must believe that there is some moral force to his claim.

Against Fuller, Hart insisted that the identification of a directive as law indicated nothing about the moral authority of that directive and thus nothing about whether that directive should be obeyed[3]. Consequently, claimed Hart, official and citizen disobedience to immoral directives would be facilitated not by pretending that such directives failed to qualify as legal just because of their perceived iniquity, but rather by internalising the fundamental positivist insight that law and morality were conceptually distinct. Because of this conceptual distinction between law and morality, Hart argued, a directive’s legality said nothing about its morality[4]

The Hart- Devlin Debate

Again, it is important at the outside to understand Devlin’s approach to law and morality, before considering Hart’s criticism of his approach. In “The Enforcement of Morals[5]” Devlin supported the view that law should not tolerate that which the reasonable man finds disgusting. Society needs a moral identity, because it is the moral values of society that make it cohere. For Devlin, even private acts of immorality can weaken the fabric of society if they are sufficiently grave.

The balance that Devlin seeks to achieve is placed in the context of the political morality of contemporary society, where toleration is itself a prime moral principle. Thus there “Must be toleration of the maximum individual freedom that is consistent with the integrity of society[6]”. Devlin’s justification for the legal enforcement of morality is an extension of the harm principle to a perceived threat to society, rather than harm to other individuals. This seems quite a reasonable proposition. However this test is one that masquerades as (1) a relevant test for the principle and (2) an objective test. Devlin’s reasonable man is not asked in sociological terms what immorality is actually threatening to society. He is asked, instead, what he feels disgust at.

Further he asserts that whilst the reasonable man test is employed as a way of alienating a courtroom issue from the subjective opinions of parties to a particular legal issue, it does not necessarily have the same effect in this situation. Devlin employs the term reasonable man to give the impression of objectivity. However it is a fiction to suggest that there is a reasonable man when it comes to difficult moral issues. The reasonable man of legal fiction is one who employs practical reason and due consideration when acting. However, all the practical reason and due consideration in the world will not change the preferences an prejudices that embody disgust. On the issue of homosexuality, many people intellectually feel that people’s sexual orientation is not a matter for legal intervention, but they nonetheless find homosexual acts to be repellent. The reasonable man test is thus a spurious validation for prevailing societal aesthetics, rather than a test of what society feels to be threatening[7].

Devlin’s view should be contrasted with the view of Hart. In Law, Liberty and Morality[8], Hart recognises that there does not seem to be any real widely shared morality, and there can be no freedom if we are compelled to accept only those things that others approve of.

Hart notes that there are certain constants of the human condition, which he terms the minimum content of natural law, such as the vulnerability of human beings. If we disregard these sociological facts it would be tantamount to suicide. But beyond these facts, society is faced with a choice of what rules to adopt in order to protect us from the frailties of the human condition[9]. Hart seems to assert that since the development of a society is a collective odyssey, the values that a society has adopted for its preservation and progress constitute a shared morality of sorts. This does not mean that the norms that a society has accepted and retained are ones that are logically necessary for the achievement of social preservation. However, they are instrumental in the maintenance of social cohesion. For this reason he would not accept Devlin’s analogy of deviation from moral norms with treason against society[10]. It may be that a change in morality can result in friction, but it need not result in the collapse of society.

Hart also adopts the harm principle, but denies that consent can be used as a mitigating factor. Equally, immoral acts in public may be harmful to others and, as such, open to legal censure, whereas acts in private should not be a matter for the law. His justification is that while the first is the legitimate prevention of harm, the latter is the enforcement of the societal will over the individual. Hart finds paternalism justified, but not enforce morality per se.


These theories forwarded create good arguments both for and against the inclusion of morality in law. A more complex case for the non-separation of laws and morals have been made more recently by Detmold:

“Hart’s mistake…. Was to try to run two incompatible analyses together; the analysis of sociological statements, where existence can be separated from bindingness and thus from moral statements; and the analysis of internal normative statements, where it cannot. The Concept of Law suffers throughout from a failure to separate these things[11]

This is a true anylasis of Hart’s theories, and it was said at the introduction that it would be concluded that morality was a necessary part of the law and indeed it was important in helping society to understand its moral obligations, this is concluded. However it is difficulty to reach these conclusions, when the definition of morality is considered, it is such an abstract concept is it even possible to pin it down to a definition? It suffices to say that there is no requirement to look outside information or reason in order to find and answer to some moral dilemmas. Often moral feelings run against he grain of other people’s views and even our own reasoning. As such, morals defined in this way are capable of producing infinite disagreement, since different people’s consciences dictate different things. Considering morals in this light suggests that there is absence of universal agreement, if this is the case, how can they effect our understanding of our legal obligations? This would mean that the legal obligations of one person are not necessarily that of another person, this said it follows that what is legally wrong finds its basis somewhere and it is suggested that this base is morality. Although it should be recognised that no all laws are moral- this means that our understanding of the legal/moral argument whilst added to by the debates of Hart, Devlin and Fuller, is not concluded, and it is unlikely that it ever will be.


Journal Articles

Curzon L, (1992) “Jurisprudence: The Hart-Fuller Debate” Student Law Review 1992 6 (Sum) 55-56

Hayry H, (1991) “Liberalism and Legal Moralism: The Hart-Devlin Debate and Beyond” Ratio Juris 4(2) 202-218

Schauer F, (2005) “The Social Construction of the Concept of Law: A Reply to Julia Dickinson”, Oxford Journal of Legal Studies 25 (493)


Devlin P, (1965) “The Enforcement of Morals”, Oxford University Press, Oxford

Detmold M J, (1984) “The Unity of Law and Morality: A Refutation of Legal Positivism”, London: Routledge & Kegan Paul

Doherty M, (2003) “Jurisprudence: The Philosophy of Law”, Third Edition, Old Bailey Press

Fuller L, (1969) “The Morality of Law” Yale (reprinted 2003)

H L A Hart, (1963) “Law, Liberty and Morality”, Oxford University Press, Oxford

Lloyd D, (2001) “Lloyd’s Introduction to Jurisprudence”, Seventh Edition, London, Sweet and Maxwell