Michel Foucault was a French thinker (he lived from 1924-1984), and as such was gloriously broad-ranging in the things he wrote about - crime and punishment, sexuality, hospitals, and all sorts. He was fascinated by the way that power operates in the stories we tell about the world and ourselves, where those stories came from, and how they change us. He didn't invent the famous pendulum - that was another Foucault - which is a bit sad, because it would be quite funny, given the topic of this post.
Foucault's History of Sexuality (or Volume 1 of it anyway, which is the only bit I've read) basically asks this: We tell ourselves a story that we are a sexually repressed society, that from the 17th century we began to be ashamed of sex, and reluctant to talk about it where before we were free and easy and happy to be bawdy. No longer comfortable telling dirty jokes, we became like the Victorians, so terrified of our own sexuality that we started covering up suggestive table legs. The twentieth century, then, has seen the beginning of our liberation from this repression, but we're still basically repressed. And yet, Foucault says, is that really what happened? Didn't the 17th century in fact see a new explosion of different ways of talking about sexuality - the emergence of psychoanalysis, of new laws regulating exactly what sort of sex was and wasn't ok, of medical names for specific perversions, of programmes designed to regulate the sexuality of children. We, Foucault says, are a society which “has been loudly castigating itself for its hypocrisy for more than a century, which speaks verbosely of its own silence, takes great pains to relate in detail the things it does not say, denounces the powers it exercises, and promises to liberate itself from the very laws that have made it function.” The question isn't “why are we repressed?” but “Why do we say with so much passion and so much resentment against our most recent past, against our present and against ourselves, that we are repressed?”
Foucault locates the start of the change in the practise of confession. Apparently, in ye olde days, confessing a sexual sin meant describing in great detail who did what to whom, in what position, the precise moment of pleasure. But from around the 17th century, they changed: less focus on practicalities, and much more on the internal things: thoughts, desires, feeling, which before had been unimportant as long as no one acted them. Sex became something much more internal, much more deeply rooted in the centre of the person, much more essential to their identity. And as sex extended throughout the whole person, Foucault argues, so did power - doctors, psychiatrists, educators, lawmakers - all were given new abilities to control and dictate behaviour and even thoughts. Sexuality was born: the idea that the nexus of thoughts, desires and preferences each person has was in some way deeply constitutive of their very self.
Where before, marital sex was much discussed and everything else seen as basically the same category of adultery/promiscuity, we began to define specific perversions, and instead of having people who did perverted things, we saw the emergence of people who were perverts - homosexuals, paedophiles, sadists, masochists (and actually, it was this creation of new positive identities for people that enabled them to fight for their rights - until we believed in gay people, instead of people who perpetrated gay acts, we couldn't really even think about gay rights).
Our sexuality isn't just there, Foucault argues - it is formed, moulded, directed and dictated by the stories we tell within our society, by the theories and laws and standards of "normality", and within these stories, power operates, controlling all of us in different ways, making us who we are, making our sexuality what it is.