The growing discourse on sex, particularly in the 19th century, had the effect of turning sex into a problem of truth. Sex was seen as something dangerous: perverse pleasures could be a threat not just to one person, but also to society as a whole. Knowing about sex became increasingly important, but it was equally important that this knowledge should take the side of common morality. Learned discourse on sex was full of distortions and downright falsehoods that supported popular prudishness toward unorthodox sexual practices. Foucault remarks that there was hardly any commerce between the study of human sexual behavior and the scientific procedures involved in the biological study of plant and animal reproduction. Rather than emphasize the biases of this learned discourse, however, Foucault points out that, within this framework of discourses, sex was no longer treated only as a matter for morality, and became treated as a matter of knowledge, and of truth and falsehood.
The modern West is not the first place to develop a discourse about the truth of sex. The cultures of Rome, China, Japan, India, and the Arabic-Muslim world, have all treated sex as an object of knowledge. However, Foucault distinguishes these societies from our own by saying they deal in an ars erotica ("erotic art") whereas we deal in a scientia sexualis ("science of sexuality").
The knowledge passed on by the ars erotica is a knowledge of sensual pleasure. The truth it contains is the truth about pleasure itself: how pleasure can be experienced, intensified or maximized. A mystique and secrecy evolves around this knowledge, and it can only be passed from an experienced master to an initiated novice. There is no question of what pleasures are permitted and what forbidden: only a question of the pleasures themselves.
The scientia sexualis, by contrast, deals with confessions extracted from the unlearned rather than secrets passed down from the learned. Since the Middle Ages, Foucault asserts, confession has become increasingly important to us. In law, we demand the confession of criminals; in literature, we relish self- conscious confession; in philosophy, we have increasingly come to see truth as something to be dug out of our own consciousness.
Now that confession has become an omnipresent aspect of our daily lives, we no longer think of the power pushing us toward confession as a constraint placed upon us. On the contrary, we have come to think of confession as a way of finding truth, a form of liberation from repressive powers that try to silence us. Foucault writes that we have become "subjects in both senses of the word": we are subjected to powers that draw confessions from us, and through confession we come to see ourselves as thinking subjects, the subject of confession.
The distinction between ars and scientia is similar to the academic distinction between the arts and the sciences. The sciences deal with the world we inhabit and the arts deal with our responses to that world. That is, the sciences encompass a set of fact that would presumably be true whether or not human beings even existed, whereas the arts deal precisely with the human response to experience. The Greek word eros denotes sexual love, desire, and pleasure. Eros refers to sex as a sensual fact, whereas sexualis refers to sex as an abstract concept. Ars erotica, then, focuses largely on sex as a human phenomenon, something we do, something we enjoy, something we desire. Scientia sexualis highlights the inhuman aspect of sex, the fact of sex as a form of reproduction that we indulge in in much the same way as animals. Ars erotica speaks from personal experience, while scientia sexualis speaks from the perspective of a distanced observer.