In Protestant Britain 400 years ago, unless you were fairly rich and powerful, it must have taken extraordinary courage to commit adultery or to fornicate. Even if you were not found out, you could be certain that an angry God knew of your sin, and unless you were sincerely penitent he would burn you for all eternity. But adultery and fornication were crimes as well as sins, and if you were caught, and especially if your crime led to the birth of a child, the consequences could be appalling.

Faramerz Dabhoiwala begins his book with an account of a couple convicted in 1612 of fornication and of producing a bastard child in the city of Westminster. They are stripped to the waist, tied to the tail of a cart, whipped from the Gatehouse Prison by the abbey all the way to Temple Bar, and there banished from the city, from their relations, their friends and their livelihoods. The strict sexual discipline imposed by the courts was popular, and it got stricter. By 1650 adultery was made a capital crime. The passions of adulterers must have been overwhelming to make them take such risks.

A hundred years later things looked very different. "A new openness about sex had transformed the culture of the English-speaking world"  at least for some. Buggery, of course, would be a capital offence for a century to come, and as at other times in history a new sexual permissiveness was not entirely good news for women. As the legal policing of heterosexual sex largely disappeared, the number of illegitimate births increased, and with it the number of women regarded as "ruined". But among heterosexual men, not just the rich and powerful but also the middle-class and moderately well-off, sexual behaviour had come to be seen as a largely private matter, with the paradoxical result that "a whole range of sexual ideas and practices, within and without marriage, was now discussed, celebrated and indulged more publicly than ever before".

This is Dabhoiwala's "first sexual revolution", and he sees it in relation partly to the movement of population from the country to the towns, where there were more places and occasions for the sexes to meet and less opportunity for the community at large to inspect and control individual behaviour. But he understands it too in relation to the enlightenment in Europe and north America, and the model it created of civilisation based on the principles of "privacy, equality, and freedom".

No one is likely to argue, but one of the good things about this book is that it does not offer to explain this revolution in terms of its supposed causes, but to place it in as wide a context as possible, as a "central part" of a model of civilisation that changed everything  the province of legislation, the influence of religion, the rights of citizens  as well as sexual behaviour and our beliefs about it. The result is an informative, wide-ranging book that is also compellingly readable.

Revolutions, of course, are never complete, and the male intellectuals in the vanguard of the sexual revolution were keen that this one would be no exception. The prohibition on polygamy was tirelessly interrogated, but no one seemed very keen to advocate polyandry, which raised questions about the inheritance of property that would have remodelled society to a much too revolutionary degree. The call to return to a legendary time when "women, and all other things were in common" was really a call to share women and nothing much else. Sexual desire was argued to be a natural appetite, like hunger or thirst, implanted by God, and which he must have intended us to satisfy; but though both men and women were meant to eat when hungry and drink when thirsty, it was surely not likely that God intended women to have sex whenever they felt like it. God had made the sexes different, and it was as "natural" for women to be chaste as it was for men to take pleasure wherever they found it.

Many writers on religion began to question the eternal punishments that a supposedly loving God was believed to visit on sexual offenders. For the libertines of the later 18th century, the new uncertainty about the dangers of hellfire transformed it from the strongest of all deterrents to a risk that put the spice into vice. But for men in public life, the greatest benefit of the sexual revolution may have been the increasing agreement that, as long as a man's sexual behaviour did not impede the fulfilment of his public duties, it was no one's business but his own.

Enlightenment thinking had a dramatic effect on how the phenomenon of prostitution was understood. The sexual liberation of well-off heterosexual men made it convenient to regard prostitution as positively necessary to the health of society, and to approach it as a social phenomenon: not just the result of the supposed moral failings of women too idle to get a proper job, but an effect of systemic ignorance and poverty. Fallen women who displayed the right kind of modest contrition became the object of fashionable charities. At the same time, it increasingly came to be seen that women become prostitutes as a result of their treatment by men, and a standard narrative begins to circulate, especially in the novel, about how prostitutes are made.

A teenage girl, the daughter of a country family of impeccable moral reputation, is spotted by a young gentleman who lays siege to her chastity with repeated promises of marriage. Hopelessly in love, the girl eventually agrees to elope with him to London. But the young gent speaks less and less of marriage, soon tires of his easy conquest, and passes her on to a friend or simply deserts her. Destitute, possibly pregnant, unable to return to her parents, she ends up on the streets.

The point of this narrative is less to condemn the behaviour of men than to persuade male and female readers alike that prostitutes are human and deserve our pity. The story fitted the new genre of the novel, which could offer a much fuller, more circumstantial account of why people behave as they do, than any previous form of literature, and was programmed to persuade us that the more we understood, the more we would forgive.

Dabhoiwala believes the novel played a vital part in changing how prostitutes came to be regarded, but I am not so sure: the tolerant morality of the novel was a frequent target of those who worried about female conduct, and even in novels themselves, novel-reading was often seen as predisposing young girls to seduction, and therefore (as the standard narrative had it) to prostitution. Respectable novelists such as Jane Austen tended to avoid the issue.

To some small degree Dabhoiwala seems to me to exaggerate his sexual revolution by allowing his eyes to drift up the social scale as his story moves forward in time. In particular, I was left wondering how far ordinary, lower-class heterosexual men shared in the freedoms enjoyed by their social superiors in the 18th century; they don't get much attention. Overall, however, he has done a wonderful job. Determined to acknowledge the limitations of the sexual revolution he describes, unwilling to minimise the advantages it brought, careful to remind us that the sexual discipline often violently enforced by some non-western cultures was, for most of its history, enforced as eagerly in the west too, Dabhoiwala has to tread a difficult path through a more or less limitless field, and he manages it with great care and unselfconscious aplomb.

 John Barrell's The Spirit of Despotism: Invasions of Privacy in the 1790s is published by Oxford University Press

Faramerz Dabhoiwala, senior fellow in history at Exeter College, Oxford, recently exhorted people to read his new book, The Origins of Sex, because "it will almost certainly improve their sex lives". Though the subtitle promises the reader "a history of the first sexual revolution"  which, according to Dabhoiwala, took place in the late 17th and 18th centuries  the book offers not a connected narrative, but a series of meditations on topics tangentially related to the history of ideas.

Perhaps because he is a member of the other place, Dabhoiwala ignores the kinds of economic, social and demographic history that were systematised at Cambridge. It is not enough to show that somebody somewhere was thinking thoughts that we might think of as amazingly progressive, without investigating whether those ideas were leavening public discourse or changing the attitudes of the multitude. Dabhoiwala's sources, 100 closely printed pages of them, are modish theoretical discussions of the topics he chooses to address. He nowhere tests his basic assumptions against actual behaviour. His ignorance of the bookselling trade, for example, leads him to confuse Grub Street productions by the likes of John Dunton, whom he mistakenly dubs "a leading journalist and bookseller", with mainstream publication.

Libertine and libertarian texts are as old as literature. Dabhoiwala's account of the tradition is less cogent because he limits himself to the English language. Historically, subversion and pornography were the province of the class of educated gentlemen who had the option of collecting and sharing dangerous and titillating works in languages that could not be read by women or servants. Ovid's Elegies, for example, were easily available in Latin. It was when Marlowe translated them into English that the book was burned.

The spread of literacy eventually breached what had been the province of an educated masculine upper class, but this is not the story that Dabhoiwala chooses to tell, perhaps because any account of the rearguard action of the Victorian authorities against the spread of sexual information would have neutralised his thesis there and then. He quotes Byron's most subversive ideas several times, apparently without realising that Byron left England in disgust in 1816 precisely because there was no hope of any kind of revolution. The rule of prurience and hypocrisy would remain unchallenged to this day. Prurience and hypocrisy are the twin forces driving the phone-hacking saga.

Inventive non-reproductive sex with catamites and concubines too was a cherished privilege of the most privileged classes in European society. In 1526, no authority was high enough to prevent or even dissuade Federigo Gonzaga from commissioning Giulio Romano to provide illustrations of naked couples copulating in 16 different positions for his private cabinet in the Palazzo del Te. It was only when the designs were engraved for print by Marcantonio Raimondi that Pope Clement VII interfered, had the plates destroyed and Raimondi flung in prison.

Some versions of Romano's sketches survived. In 1527, when Pietro Aretino supplied 16 Sonetti lussuriosi (in the language of the common people) to accompany the engravings, the second edition was seized and destroyed. And yet Aretino's Postures, as they came to be called, were famous all over Europe. The only artist mentioned by Shakespeare is "that rare Italian master Julio Romano". Dabhoiwala mentions Aretino once, apparently imagining that he was some kind of classical writer to be quoted only by the pretentious.

Sexual revolution or no, there is still no useful English translation of Aretino's Postures. In 2008, prior to a Cadogan Hall performance of Michael Nyman's setting of 8 Lust Songs from the Sonetti lussuriosi, the management hastily ordered the withdrawal of the concert programmes, because they provided an English translation of the poems: Aretino is still too hot for the English to handle.

Dabhoiwala spends so much time reading about libertine literature, he barely registers that the vast mass of publication in print in the English-speaking world between the 16th and 18th centuries is religious in character. Pornography was always available for those who sought it out; the difference is that in the 21st century pornography is as ubiquitous as religion once was. Its sadomasochistic stock in trade is still the same. No sexual revolution will happen until the role of penetration as a mechanism of domination is obliterated, until it makes no sense to snarl at anyone: "Get fucked", until "fucked" does not mean "ruined".

Sexual culture is so protean that we can hardly generalise about it; parents' attitudes are different from their children's and their children's attitudes may be different from one another's; kids in one school bus will be shocked and horrified at what is going on in another. Sex is simultaneously suppressed and commoditised. Its expression is both covert and blatant. Nowadays, masturbation is supposed to be good for us and yet "wanker" is a word of withering abuse. When sex is a duty, it palls; when it is absolutely forbidden, it becomes unbearably exciting.

Most of us might imagine that, across human history, there is a fairly constant oscillation between the powers of repression and expression; Dabhoiwala is convinced of an underlying trend. His approach commits him to bizarre generalisations; when he cites the case of a man and a woman condemned to flogging for fornication in 1612, we learn that for "most of western history" the public punishment of such offenders was "a normal event".

Shakespeare's brother Edmund, a poor player, fathered a bastard child, owned it, had it christened and buried in his parish church, but we heard nothing of any flogging for him or the child's mother. Nearly one-third of women married in Shakespeare's parish church in the 1560s were pregnant. Dabhoiwala's contention that "since the dawn of English civilisation the courts and the church had enforced the principle that illicit sex should not be tolerated by the community" is simply not true. What is true is that religious and secular authorities made fitful attempts to enforce laws against illicit sex, often for crass ulterior motives. For many years, the landlord who collected the rents from the stews of Southwark was none other than the Bishop of Winchester.

Condemnations of fornication can be found in every epoch. How they relate to actual practice is virtually impossible to establish, but Dabhoiwala will treat them as evidence. Church fathers may inveigh against premarital pregnancy but until we examine church registers to see how often infants were baptised within months or even weeks of the parents' wedding, we can't be sure that anyone was listening. When people do start listening, as they did in England at the turn of the 16th century, we have to try to work out why.

Rich men have always got away with producing bastards as long as they picked up the tab; condemnations of bastardy are usually prompted by concern about a tribe of bastards having to be raised "on the parish". Only when economic interests and outrage coincide will the result be systematic persecution. When half the townspeople are already on poor relief, the church and the corporation have good reason to join forces in persecuting unwed mothers. That persecution continues to this day, as successive governments redouble their futile efforts to stamp out teenage pregnancy.

For Dabhoiwala, "the whole of western history" begins somewhere in the middle ages, but every gentleman learned his vices from reading Petronius, Ovid, Martial and Virgil in his impressionable adolescence. He also learned how to vilify his political opponents by depicting them as repulsive lechers. Dabhoiwala quotes Rochester's famous lampoon of Charles II, whose sceptre and prick were of a length  apparently without realising that in the poem, the king's fictive priapism stands for his lust for absolute power. Obscenity has been an essential tool of political satire at least since Juvenal. As a way of discrediting a political opponent, the imputation of sexual irregularity is as effective in the fatness of these pursy times as it ever was. Ambitious gay male politicians are still having to get married  to women. Plus ça change