For ordinary people, however, law reform in these matters is not the neutral thing that Mill and his followers suppose it to be. To discover that the law no longer enforces a moral prohibition that is fundamental to your worldview is to suffer a kind of existential challenge: a sense of being cut off from the public space, so as to enter it unprotected. This feeling is part of the daily diet of Muslims in Western society, and we ought by now to be grown up enough to acknowledge it. I am not saying such a feeling is right or appropriate in our current circumstances. But it is natural, all the same, and the proof of this lies in the fact that self-declared liberals are also subject to it. When the Labour Party took office in 1997, the House of Commons was suddenly filled with people animated by left-liberal causes, many of them concerning the extension of the permissive agenda in matters of sex. During the next decade we saw the age of consent for homosexual intercourse lowered from 18 to 16, legislation to permit the teaching of homosexuality as an "option" in schools and legislation introducing "civil unions" and quasi-marital rights between homosexual partners. All this was supported with arguments of the kind advanced by Mill, to the effect that "you may think it immoral; but if you cannot prove that it harms anyone, you cannot forbid it."

At the same time, however, when it came to animals, our legislators took quite the opposite view. One of their number introduced a private member's Bill to ban fur farming, which was subsequently converted into government policy. The arguments given for the Bill, which had the support of a majority in the Commons, carefully avoided all mention of liberty, rights and harm. Those concepts belong, after all, to the opposition, which could reasonably claim that the liberties of fur farmers were being curtailed, with no proof of harm to other people - and, incidentally, no proof of harm to the animals either. The arguments given for the Bill hinged on something called "public morality". By this was meant "the aspect of morality with which the law rightly concerns itself, with a view to improving the observable conduct of the nation". To rear animals for their skins, when these were to be used entirely for the production of luxuries, was regarded as so offensive to "public morality" that it was well within the remit of a democratic state to pass a law forbidding it.

It goes without saying that this argument reverses at a stroke the jurisprudential foundations of legal reforms concerning sexual offences. When Hart and Devlin argued over "the enforcement of morals", it was in the wake of the case of Shaw v. DPP (1961) 2 A.E.R. 446. (1962) A.C. 223, in which the publication of a "ladies' directory" - an act of extraordinary innocence in comparison with the daily diet of today's internet - was held to be a criminal offence, because it was an offence to something called "public morals". Liberal opinion at the time objected strongly to the phrase "public morals", as though there were an aspect of morality that somehow escaped the confines of the private conscience to roam at large in the public world, looking for actions to punish.