Law and morality — the Hart–Devlin debate

The Hart–Devlin debate is the canonical modern English debate about legal moralism: whether the criminal law may properly be used to enforce conventional morality merely because it is conventional morality. It is not a debate about whether law and morality ever overlap. Nor is it a debate about whether legislators may act on moral reasons. Hart and Devlin both accepted that law often reflects moral judgment and that some morally wrongful conduct may properly be criminalised. The disagreement concerns a narrower but fundamental question: is the immorality of conduct, as judged by the ordinary moral feelings of the community, itself a sufficient reason for criminal prohibition?

Devlin answered, in substance, yes. He argued that every society depends upon a shared morality: not merely shared preferences, but moral bonds without which social existence disintegrates. Since the law may protect society against external attack and internal disorder, it may also protect society against practices which threaten its moral structure. This was not presented as a licence for every moral prejudice. Devlin required the reaction of the reasonable person, not private bigotry, and he insisted upon standards of intolerance, indignation and disgust. But he did maintain that moral disintegration is a public harm which law may forestall.

Hart answered, in substance, no. Drawing on Mill, Hart argued that the fact that conduct is immoral, even widely and sincerely thought so, does not by itself justify coercive criminal prohibition. The criminal law needs a more specific public justification: prevention of harm, protection from exploitation, preservation of public order, or sometimes protection from serious offence. Hart’s central concern was the distinction between positive morality — the morality actually accepted by a community — and critical morality — the morality which withstands rational scrutiny. Devlin’s appeal to shared moral feeling, Hart argued, risks mistaking social repugnance for reasoned justification.

For Cambridge Part II purposes, the importance of the debate is threefold. First, it tests the relation between legal positivism and political morality. Hart’s positivism does not entail moral indifference; it enables critical evaluation of law from outside the law’s own validity criteria. Secondly, it links jurisprudence with criminal law, rights, and constitutional adjudication: obscenity, homosexuality, sadomasochistic injury, assisted dying and privacy all raise variations of the same issue. Thirdly, it exposes a recurring methodological problem in legal theory: should political justification begin from social practices and their sustaining conditions, or from individual liberty and the burden of justification imposed on coercion?

In an examination essay, avoid reducing the debate to slogans. Devlin is not simply authoritarian; Hart is not simply permissive. Devlin offers a social thesis about the conditions of political association. Hart offers a liberal thesis about the justificatory limits of coercion. The best answers test both theses against examples and against later developments: Dworkin’s attack on appeals to conventional morality, Feinberg’s refinement of the harm principle, Raz’s perfectionist liberalism, and the Human Rights Act’s turn to legality, proportionality and private life.

The immediate context was the Report of the Committee on Homosexual Offences and Prostitution, chaired by Sir John Wolfenden and published in 1957. The Wolfenden Committee recommended that consensual homosexual conduct between adults in private should no longer be a criminal offence. Its most famous proposition was that there must remain a realm of private morality and immorality which is not the law’s business. That proposition did not assert that the conduct was morally good. It asserted that criminal law was an improper instrument for policing consensual adult sexual conduct in private.

The background matters. Mid-twentieth-century English criminal law contained offences rooted in Victorian and Edwardian moral regulation: obscenity, soliciting, homosexual offences, public indecency, and offences associated with brothels and prostitution. The criminal process was not merely protecting persons from violence or theft; it was also marking certain sexual and expressive practices as public wrongs. The Wolfenden Report therefore raised a constitutional and jurisprudential question: when Parliament criminalises conduct because it is regarded as immoral, what kind of reason is that?

Devlin entered the debate in his 1959 Maccabaean Lecture, later developed in The Enforcement of Morals. His intervention was partly a response to Wolfenden’s separation between crime and sin. He argued that the report understated the law’s legitimate concern with the moral fabric of society. Society, in Devlin’s view, is not merely an aggregation of individuals under a common police force. It is constituted by common ideas about how its members should live. If shared morality is part of what makes a society the society it is, then deliberate legal neutrality towards practices thought to undermine that morality may be a failure of self-preservation.

Hart’s reply, Law, Liberty and Morality, appeared in 1963. Hart’s argument was sharpened by his broader jurisprudential project. In The Concept of Law he had separated the existence and validity of law from its moral merit. In the Devlin debate, that separation becomes politically important: because law is not necessarily moral, the moral justification of coercion must be argued rather than assumed from social consensus. Hart did not defend moral scepticism. He defended the liberal proposition that coercive state power requires a justification more demanding than the assertion that most citizens feel disgust or indignation.

The legislative sequel was partial and cautious. The Sexual Offences Act 1967 decriminalised, in limited circumstances, homosexual acts in private between men over the then age threshold. That statute was not a full triumph of Hartian liberalism: it retained restrictions and left broader social stigma untouched. Nevertheless, it signalled that private sexual morality could no longer be treated as straightforwardly criminal merely because conventional opinion disapproved.

The judicial sequel was more ambivalent. Shaw v DPP and Knuller appeared to vindicate Devlinian themes by recognising, or at least preserving, common law powers over public morals. Later, R v Brown showed that English criminal law remained willing to treat consensual adult sexual conduct as criminal where serious injury was involved and where the court characterised the conduct as harmful to public morality or social welfare. Conversely, Strasbourg privacy jurisprudence, beginning with Dudgeon v United Kingdom, gave legal form to the Wolfenden-Hart claim that private consensual sexuality lies within a protected sphere.

For Part II, the historical context should not be treated as antiquarian. The debate recurs wherever the state invokes morality to limit liberty: pornography, prostitution, drug use, religious offence, same-sex intimacy, gender and sexuality, assisted dying, surrogacy, and public order. The institutional setting has changed — from parliamentary sovereignty and common law moralism to Convention rights and proportionality — but the core question remains whether coercion may be justified by moral disapproval alone.

1. The distinction between positive and critical morality. Hart’s most important analytic move is to distinguish the morality actually accepted by a society from the morality which is justified on reflection. Positive morality is a social fact: what people believe, condemn, tolerate or celebrate. Critical morality asks whether those beliefs are defensible. Devlin’s argument begins from positive morality, although he tries to discipline it through the perspective of the reasonable person. Hart’s objection is that ordinary moral consensus may embody prejudice, ignorance or fear. The mere fact that a practice causes disgust does not show that it is wrong, still less that it should be criminal.

This distinction connects directly with earlier weeks. Hart’s positivism separates legal validity from moral merit; it therefore makes room for external criticism of law. Natural law theories, by contrast, are more likely to insist that law’s authority is internally connected to moral reason. Dworkin’s interpretivism complicates the picture: legal rights may depend upon the best moral interpretation of legal practice, not merely upon enacted rules. In the Hart–Devlin debate, however, the central issue is not the validity of law but the justification of criminalisation.

1. The harm principle. Hart’s liberalism is Millian but not mechanically Mill’s. The harm principle says that coercion is justified to prevent harm to others, not merely to make people morally better or to save them from self-regarding vice. Hart accepts qualifications: paternalism may sometimes be justified, especially where consent is impaired or choices are not fully voluntary; public indecency and nuisance may be regulated; exploitation may be prevented. The important point is that these are independent reasons. They are not reducible to the proposition that the conduct is immoral.

1. Legal moralism. Legal moralism is the view that the immorality of conduct can itself be a reason for criminalisation. There are stronger and weaker versions. Strong legal moralism says immorality is sufficient reason, subject only to practical limits. Weak legal moralism says immorality is relevant but not conclusive. Devlin is often read as a strong conventional moralist, though this requires care. He does not say that every sin must be criminalised. He says that society may use law to preserve the moral consensus on which its existence depends. His claim is not primarily perfectionist — the state promoting the good life — but preservationist — the state defending the conditions of social life.

The case law does not map neatly onto Hart and Devlin. English courts have not usually announced themselves as Hartian liberals or Devlinian moralists. The cases are important because they show how courts have converted abstract claims about morality into doctrines of criminal liability, privacy, public policy and proportionality.

Shaw v DPP is the most Devlinian case in tone. The House of Lords upheld liability connected with the publication of a directory of prostitutes and endorsed a common law offence of conspiracy to corrupt public morals. Viscount Simonds’ language suggested that courts retained a residual power to conserve the moral welfare of the state. For jurisprudence, Shaw is not important because of its facts alone; it is important because it treats public morality as an object of legal protection in itself. Hart criticised this mode of reasoning as giving judicial effect to moral disapproval without sufficient democratic or liberal constraint.

Knuller is more cautious but no less revealing. The House of Lords declined to overrule Shaw, preserving the offence of conspiracy to corrupt public morals. Yet several speeches were uneasy about judicial creation of broad moral offences. Knuller therefore illustrates the tension between legality and moralism: even if society may protect morals, should judges define the relevant morality through open-ended common law crimes? This raises rule of law concerns that are independent of Hart’s substantive liberalism.

Dudgeon v United Kingdom marks a decisive rights-based challenge to legal moralism. The European Court of Human Rights held that Northern Irish criminalisation of consensual homosexual conduct in private violated Article 8. The Court accepted that protection of morals was a legitimate aim, but held the interference disproportionate. That is not the same as saying morality is irrelevant. It is saying that moral disapproval cannot automatically outweigh private life. The case gives institutional form to a Hartian presumption: the burden lies on the state to justify intrusion into private adult intimacy.

R v Brown is the principal modern English counterpoint. The majority held that consent was no defence to charges arising from sadomasochistic activities causing actual bodily harm or worse. The judgments invoked public interest, injury, cruelty and moral considerations. Brown is often used in essays to show the limits of simple libertarianism: the conduct was private and consensual, yet the law intervened. But it also shows the dangers of moral characterisation. If the result turns on serious harm, Hart may accommodate it. If it turns on disgust at homosexual sadomasochism, it looks Devlinian.

Pretty and Nicklinson move the debate from sexuality to autonomy and death. In both, the courts treated assisted dying as an area where private autonomy, sanctity of life, protection of the vulnerable and institutional competence interact. These cases do not fit the Wolfenden paradigm of harmless private vice. The moral disagreement is deeper: whether the law should respect autonomous choice to die or maintain an absolute prohibition because of risks to others and the symbolic value of life. They show that Hart’s harm principle is a starting point, not a complete constitutional theory.

The cumulative lesson is that modern law has not abolished morality. It has required moral claims to appear in more disciplined forms: harm, vulnerability, exploitation, dignity, rights of others, proportionality and public reason. The Hart–Devlin debate remains the conceptual frame for asking whether those forms are genuine justifications or merely conventional morality in translated language.

See practice questions section below.

See further reading section below.