Sexuality isn't a "thing" that is then repressed by power, or that must be discovered through careful investigation. Sexuality is a social construct that channels a variety of different power relations. Our concept of sexuality is built by the strategies that make use of it: it serves as a network that joins together physical sensations and pleasure, the incitement to discourse, the formation of specialized knowledge, and political controls and resistance.
Foucault identifies four centers that have related power and knowledge to sex. First, the "hysterization of women's bodies" has led us to think of the female body first as highly sexual and second as an object of medical knowledge. The female body, as a center for reproduction, has also come to be considered a matter of public interest and public control. Second, the "pedagogization of children's sex" sees children as highly sexual creatures, and sees this sexuality as something dangerous that needs to be monitored and controlled. Third, the "socialization of procreative behavior" sees reproduction and therefore sex as a matter of public importance, and disapproves of non- procreative sex. Fourth, the "psychiatrization of perverse pleasure" is the result of studying sex as a medical and psychiatric phenomenon. It highlights divergences from normal sexual behavior and identifies them as illnesses that need correcting. Foucault emphasizes that these four centers do not "repress" sexuality; the concept of sexuality does not exist except as it is framed by these discourses.
Foucault distinguishes between what he calls the "deployment of alliance" and the "deployment of sexuality." The former is a system of kinship ties that exists in almost every culture. It consists of a number of spoken or unspoken rules regarding marriage, family ties, ancestry and so on. The latter, which has increasingly come to replace the former in modern society, is far less regulatory and far more variegated. While the deployment of alliance essentially works to maintain the stable structure of society, the deployment of sexuality provides an ever-changing structure that allows us to interpret a range of phenomena in their relation to sex and pleasure. Foucault suggests that the deployment of sexuality evolved from the deployment of alliance, as the earlier emphasis on what sorts of relations were permitted was replaced by an emphasis on what sort of sensations were permitted.
All four strategic centers deal with family relations. Foucault concludes that the family does not repress sexuality, but nurtures it. The deployment of alliance focuses specifically on family relations, so it is in the family that the deployment of alliance and the deployment of sexuality have the most contact. Foucault suggests that the deployment of alliance maintains some control over family relations and thus on the deployment of sexuality by means of the taboo it places on incest.
Foucault traces the emergence of sexuality to the seventeenth century, where the Christian emphasis on sins of the flesh led to an increasing awareness of sexuality in family relations. The system of alliance, in trying to regulate this new sexual intensification of family relations, brought in the advice of doctors, priests, and educators. This attempt at regulation only helped to spread the discourse on sexuality, and consequently sexuality itself. Our discourse on sexuality is still used to maintain the set of laws and taboos laid out by the deployment of alliance. While sexuality was born out of this alliance, it is now used to support the alliance.
Characterizations of sexuality share a perception of sexuality as a thing that exists, in some sort of way, in the world. Regardless of who we are, how we think, or what we talk about, our sexuality would still take a form similar to the one it takes now. We perceive our sexuality as something we can discover or not discover, but that is not deeply affected by our discovery of it. We think of sexuality in the same way that we might think about consciousness: it is not a material "thing," but it is an aspect of who we are, and has an existence independent of how we talk about it. Foucault thinks this conception of sexuality commits a category error. It is like identifying a verb as a noun and then discussing what kind of a noun it is. Sexuality, according to Foucault does not exist in us in the way our consciousness exists in us. Rather, he asserts, it is a construct that has grown out of certain kinds of discourse. In this sense, it is something like a co-ordinate system in geometry: it is a system that helps us gain a particular perspective on an issue.