How we perceive the past, what we see in it and what we ignore, depends on our current perspective. Anyone who has looked back over their own life at various points will appreciate that. It is equally true of historical writing: the past looks different to different histor­ians and at different times. This book grew out of my attempt to understand the profound chasm between our present attitudes to sex and those that prevailed for most of western history. In describing this change I have highlighted the themes and the time-frame that seemed to me most evidently important, and concentrated on the views of the educated middling and upper classes of the period. This was not a democratic world: its public culture was disproportionately shaped and controlled by these dominant social groups. Yet, as I have tried to show, it was also an increasingly open and pluralist society, in which sexual attitudes were far from uniform.

Other scholars and scientists take different perspectives. Some would lay greater stress on the limits of sexual discipline before the eighteenth century, or on its continued strength thereafter, or on varia­tions between sexes, classes, and regions. Others assert that the most fundamental aspects of sexual behaviour are neurologically hardwired into our brains, so that studying the history of sexual attitudes doesn’t reveal anything significant. But that is like saying that politics is always about the pursuit of power, without trying to understand how govern­ment evolved from tribal conflict to parliamentary democracy, or why even today it takes such different forms around the world.

How we view the past equally shapes how we see the present. The argument of this book has been that the origin of modern western attitudes to sex lies in the great intellectual and social revolutions of the eighteenth century. For well over a thousand years, from the early middle ages to the seventeenth century, the enforcement of ever – stricter public discipline over sexual behaviour was a central preoccupation of every Christian community across the globe – yet by 1800 this had been replaced by a fundamentally different outlook. This radical transformation laid the ground for the sexual culture of the Victorians, of the twentieth century, and of our own day.

The most basic modern novelty was a perennial indeterminacy about the limits of sexual freedom. In place of a relatively coherent, authoritative world view that had endured for centuries, the Enlight­enment left a much greater confusion and plurality of moral perspectives, with irresolvable tensions between them. That has been part of our modern condition ever since. So, too, have been the growth of sexual liberty; the increasing dominance of urban ways of living and discussing sex; the presumption that men are naturally more sex­ually active and women more passive; an enduring association between morality and class; and our endlessly fluctuating obsessions with ‘natural’ and ‘unnatural’ behaviour, pornography and celebrity, and the distinction between the ‘public’ and the ‘private’. These have been the dominant themes of nineteenth – and twentieth-century sex­ual culture. Only by looking back at the transition from the pre-modern to the modern world can we properly understand where they came from.