I was preoccupied by a number of puzzles during the time I was researching and writing Sexuality in Europe: A Twentieth-Century History. Among other things, I was interested in the puzzle of historical causation. I was curious to use the tools of comparative history as well as the study of transnational flows of people and ideas, and of market forces and wars and diplomatic pressures, to understand what particular conjunctions of multiple factors may have caused sexual cultures (including laws, behaviours, and values) to move either in more liberal-progressive or more neotraditionalist-conservative or overtly repressive directions. At the same time, and throughout, I was all too acutely aware that ‘sexuality’ – that elusive and contested ‘it’ – was and is precisely one of those realms of human existence that continually defy and confuse our assumptions about what exactly constitutes restriction or liberation. I was thus also especially interested to reconstruct as well as possible, using the broadest range of types of sources, how exactly people in the past expressed how they imagined and experienced whatever they thought sexuality was and, in addition, how they battled over the ethics of sexual matters. On the one hand, sexuality – like faith or work – is one of those phenomena in which representations and reality are inevitably inextricable, and I was constantly fascinated with how people grappled with that inextricability, in all its complex manifestations. After all, not only what was considered appropriate or normal or good (in the eyes of God, or the neighbours, or the doctors, or the activists, or the popular advice-writers), but also what was considered (or even physiologically felt) as anxiety-producing or immoral and/or – not least – as sexually thrilling or deeply satisfying has clearly varied considerably across time and place. On the other hand, I was particularly interested in the recurrent and remarkable gaps between lived experiences and personal, private insights, and that which was perceived to be publicly, politically defensible. The gap between the quietly lived and the openly articulable could be stark; it often took tremendous courage to defend sexual freedom, in dictatorships certainly, but also in democracies. I therefore also paid special attention to how those defences were framed, in each place and moment, and with what intended and unintended effects. So while the twentieth century in Europe is often called ‘the century of sex’ and seen as an era of increasing liberalisation, I was convinced of the need to complicate the liberalisation paradigm.