Hart identified the need to clarify "the understanding of law, coercion, and morality as different but related social phenomena". Lord Patrick Devlin attempted to provide this clarification, on the relationship between the law and the prevailing moral climate in a society, by posing the following three questions:
“Has society the right to pass judgment at all on matters of morals? Ought there, in other words, to be a public morality, or are morals always a matter for private judgment?”
“If society has the right to pass judgment, has it also the right to use the weapon of the law to enforce it?”
“If so, ought it to use that weapon in all cases or only in some; and if only in some, on what principles should it distinguish?” 
His own answer to the first question is as follows:
“…society is not something that is kept together physically; it is held by the invisible bonds of common thought. If the bonds were too far relaxed the members would drift apart. A common morality is part of the bondage. The bondage is part of the price of society; and mankind, which needs society, must pay its price”.
In this book the Legal and Moral Dimensions of power are analysed separately, so the need for "public morality" was addressed in the previous chapter (4.4.2), where it was argued, in agreement with Devlin, that some common standards for socially-acceptable behaviour can be agreed – even in a pluralist society.
To Devlin's second question, whether society "has the right to use the weapon of law to enforce" public morality, he gave this answer:
“…it is not possible to set theoretical limits to the power of the State to legislate against immorality. It is not possible to settle in advance exceptions to the general rule or to define inflexibly areas of morality into which the law is in no circumstances to be allowed to enter. Society is entitled by means of its laws to protect itself from dangers, whether from within or without.” 
The concept of society being constitutionally “entitled” to use the law to protect itself from dangers is not contentious in itself, but Devlin fails to address the question of topics where legislation risks being unacceptable to portions of the population – particularly in a pluralist society – as discussed later in this chapter (5.4.3).
Devlin's own answer to his third question, of when to use the “weapon of law” to enforce “public morality”, is highly contentious. It is given in two parts:
“Immorality then, for the purpose of the law, is what every right-minded person is presumed to consider to be immoral”;
“Nothing should be punished by the law that does not lie beyond the limits of tolerance. It is not nearly enough to say that a majority dislike a practice; there must be a real feeling of reprobation.”
He provides further definition on "every right-minded person" by appealing to the concepts of "the man in the street", “the man in the Clapham omnibus” or “the man in the jury box”. This book is addressing questions of governance in the 21st century, where pluralism is increasingly a reality, and it cannot be assumed that one would get consistent answers from "the man in the street" – so there is a problem in using the "reprobation" of the majority as a basis for law. As Hart pointed out, there are “points at which thought is needed before we turn popular morality into criminal law”. There is a balance to be struck, between individual freedom and the desire for legislation, particularly on morally controversial issues – which is another topic discussed later in this chapter (5.4.4).
Devlin failed to provide a critical analysis of what constitutes a real danger to society and where the use of the law is appropriate. He did, though, usefully characterise the relationship between the law and morality:
“We all recognize the gap between the moral law and the law of the land. No man is worth much who regulates his conduct with the sole object of escaping punishment, and every worthy society sets for its members standards which are above those of the law. We recognize the existence of such higher standards when we use expressions such as 'moral obligation' and 'morally bound'.”
He thus endorsed the position taken in this book: that the Legal and Moral Dimensions are different and that the Moral Dimension has a wider scope. Leonard Read observed that the “external government”, or what he called “the law without” which is provided by the Legal Dimension of governance, is not a substitute for the Moral Dimension: “the law without has but a limited competence when it comes to controlling—let alone improving—behavior”.
Those aspects of behaviour which are within the scope of the law are more strongly enforced, using the coercive power of the State, and have both a Legal and a Moral Dimension. Several considerations come into play when deciding whether to legislate, as illustrated by the example of litter:
· Some people might find it morally acceptable to drop litter, perhaps thinking: ‘I want to drop litter and I don't mind if you do. We pay our taxes, so someone else will pick it up’.
· Other people find the litter offensive and don’t want to pay more tax.
If this problem is left purely in the Moral Dimension, there is a risk of someone provoking conflict by asking a stranger to refrain from dropping litter. The existence of a law demonstrates society’s contractual agreement to condemn the practice; it reinforces people's right to ask others to change their behaviour; it allows them to call for law enforcement rather than take the risk of trying to exert moral pressure themselves; and the existence of the law acts as a deterrent to prevent the behaviour.
In terms of cause and effect, the relationship between law and morality varies. Legislators in Britain led the abolition of capital punishment in 1965, but they were responding to a change which was already beginning in the case of the 1967 Sexual Offences Bill – as described by Andrew Marr: 
“Though there was still formidable public support for hanging, MPs were becoming increasingly unhappy about it. Silverman formed a national campaign to end the death penalty.”
“[With the Sexual Offences Bill] politicians were reacting to a changing mood, if not among the whole public, then at least among what would later be called with easy disparagement, the chattering classes.”
Irrespective of whether the law is leading or following public opinion, it is adding a coercive element to the operation of the Moral Dimension.
© PatternsofPower.org, 2014
 H.L.A. Hart, The Concept of Law, Preface.
 Lord Patrick Devlin, Morals and the Criminal Law, pp. 72-79.
 Lord Patrick Devlin, Morals and the Criminal Law, p. 76.
 Lord Patrick Devlin, Morals and the Criminal Law, pp. 78 and 80.
 H.L.A. Hart, Immorality and Treason, p. 85.
 Lord Patrick Devlin, Morals and the Criminal Law, p. 82.
 This quotation comes from Leonard Read’s essay The Law Without, from Four Essays. These were available in April 2014 at http://smeedonstate-ism.com/Library/Four%20Essays%20by%20Leonard%20Read.pdf.
 Andrew Marr's accounts of the abolition of the death penalty and the Sexual Offences Bill appeared in his book A History of Modern Britain (pp. 251-4).
The Sexual Offences Act of 1967 belatedly followed the 1957 Wolfenden Report, as Jeffrey Weeks explained in a report entitled Wolfenden and beyond: the remaking of homosexual history, which was published on the History & Policy website and was available in April 2014 at http://www.historyandpolicy.org/papers/policy-paper-51.html. His report noted the extent of the cultural change which was achieved both then and subsequently:
“In the 1950s Britain was widely regarded as having one of the most conservative sexual cultures in the world, with one of the most draconian penal codes. Today it has one of the most liberal and tolerant.”