Even Freud was agin it

The distinguished Swiss doctor S. A. D. Tissot believed it to be more dangerous than smallpox. Kant thought it was worse than suicide. Other distinguished luminaries of the Enlightenment saw it as the cause of general debility, moral corruption and premature death. Masturbation, the solitary, secret vice, had a dramatic career, from round about 1712, as Thomas Laqueur dates it in this important book, to roughly the first world war, as the gateway to numberless, often nameless horrors. Quacks and pornographers made fortunes from the new taboo. Philosophers constructed moral systems around the obloquy that sex with oneself produced. Meanwhile, generations of young people, male and female, had their sexual lives blighted by the fear inculcated in vulnerable minds by the torrents of medical expertise, moral instruction and popular mocking targeted at the most common, least harmful, most privatised erotic activity in the world. Why?

Historians have long been puzzled by what might be called the moment of masturbatory madness. Beginning with the publication of Onania - "an 88-page tract, by a profit-seeking quack doctor cum pornographer" - sometime between 1708 and 1716, a new sexual pathology, with an awesome ability to generate guilt, shame and anxiety, emerged. After a murky but rapidly growing adolescence, the new disease reached maturity and respectability in 1760 with the publication of the French edition of Tissot's Onanism , which became a literary sensation across Europe.

Thereafter, there was no holding back. Masturbation was launched into the mainstream as a serious malady, and solitary sex became the target of passionate polemic and of medico-moral intervention. Only in the 20th century were the doubts aroused by what Alex Comfort called the "anxiety makers" listened to. Today, in a culture of omnipresent pornography and the worldwide web, which consecrates universal incitements to solitary sex, the idea of masturbation as an appalling disease seems an insanity, testimony of a more oppressive and repressive age.

Laqueur's brilliant study takes this topic in sexual studies - the rise and fall of masturbation as a sexual pathology - and subjects it to the best sort of contemporary historical scholarship, combining historical detective work and detailed explication with a long view. He identifies the author of Onania as John Marten, a surgeon and quack, who had been prosecuted in 1708 for obscenity. But such details are incidental to a wider attempt to understand the genealogy of the new disease. Laqueur shows that what emerged in the early 18th century was a new way of conceptualising masturbation, fundamentally different from the ways in which solitary sex was seen in classical, Jewish or Christian traditions. The result is not only illuminating about the main topic, but becomes a way of understanding western sexual history as a whole.

In part, this is a continuation of the project of Laqueur's earlier book, Making Sex (1990), which explores the ways in which the long-established concept of one gender shifted in the 18th century towards the dualistic, complementary system of "two sexes" we take for granted today. The timelines are similar in this analysis of solitary sex, with the age of Enlightenment as the crucial turning point. The timing is crucial because it undermines the idea that masturbation was tabooed as an enactment of irrational repression. In fact, the best minds of the age, and the most fervent advocates of unshackling the chains of unreason, were enthusiastic supporters of the new understanding of masturbation. The fear of masturbation needs to be understood as more than a temporary aberration of a dark past. Rather, it can only really be understood, Laqueur suggests, as integral to the Enlightenment project itself, to the birth pangs of modernity.

Masturbation, says Laqueur, is the sexuality of the modern self. It is protean, unbounded, limited only by imagination. It is the sexuality of secrecy, privacy and excess. It is self-governed, autonomous, autarchic. It is the sexuality of fantasy. It is a denial of the social. This is what made sex with the self such a threat to the doctors, theorists and moralists of the 18th century. It represented the pursuit of pleasure without social ties or mutual obligation. It threatened the delicate ties of civil society that Enlightenment worthies sought to strengthen to moderate the stark opposition of state and society. It represented the genie of selfishness unleashed by the new world of commerce and individualism. The onanist was the alter ego, the nasty brother and sister, of the modern self struggling to be born. Masturbation was the vice of individuation in a society where the old ramparts against uncontrolled desire had crumbled. It pointed to a world of solipsism that denied moderation, real autonomy and reason.

Yet the effect of this tirade against meaningless freedom was to blight countless lives, inhibit sexual happiness, impose a medico-moral hegemony over the erotic as a replacement for clerical interference, and delay, rather than speed up, the working through of an individual, secular, sexual ethics to replace the vacuum left by the decay of religion and of a hierarchical social order. So powerful was the legacy of Marten, Tissot and the Encyclopaedists who embraced their ideas, of Rousseau, Kant and countless doctors, schoolmasters, scoutmasters and other zealots, that it became almost impossible to escape their embrace. Even Freud, who re-wrote the story of auto-eroticism to make it the root of all sexuality, could not escape the feeling that masturbation must have some harmful effects.

Solitary sex, Laqueur argues, is consistently seen as a problem in the context of the cultural flux produced by rapid social and economic change.

Today, we are in the midst of massive cultural transformations, but it is a world in which sex with the self has found its destiny - not as the gateway to vice, but as the royal (super) highway to private pleasures and infinite fantasy. The joy of masturbation, as Quentin Crisp quipped, is that you don't have to dress up for it. That was what Enlightenment polemicists feared. In the world of what Dennis Altman calls "global sex", that has become its justification.

Jeffrey Weeks is professor of sociology, at South Bank University.