Among the many topics explored by the philosophy of sexuality are procreation, contraception, celibacy, marriage, adultery, casual sex, flirting, prostitution, homosexuality, masturbation, seduction, rape, sexual harassment, sadomasochism, pornography, bestiality, and pedophilia. What do all these things have in common? All are related in various ways to the vast domain of human sexuality. That is, they are related, on the one hand, to the human desires and activities that involve the search for and attainment of sexual pleasure or satisfaction and, on the other hand, to the human desires and activities that involve the creation of new human beings. For it is a natural feature of human beings that certain sorts of behaviors and certain bodily organs are and can be employed either for pleasure or for reproduction, or for both.
The philosophy of sexuality explores these topics both conceptually and normatively. Conceptual analysis is carried out in the philosophy of sexuality in order to clarify the fundamental notions of sexual desire and sexual activity. Conceptual analysis is also carried out in attempting to arrive at satisfactory definitions of adultery, prostitution, rape, pornography, and so forth. Conceptual analysis (for example: what are the distinctive features of a desire that make it sexual desire instead of something else? In what ways does seduction differ from nonviolent rape?) is often difficult and seemingly picky, but proves rewarding in unanticipated and surprising ways.
Normative philosophy of sexuality inquires about the value of sexual activity and sexual pleasure and of the various forms they take. Thus the philosophy of sexuality is concerned with the perennial questions of sexual morality and constitutes a large branch of applied ethics . Normative philosophy of sexuality investigates what contribution is made to the good or virtuous life by sexuality, and tries to determine what moral obligations we have to refrain from performing certain sexual acts and what moral permissions we have to engage in others.
Some philosophers of sexuality carry out conceptual analysis and the study of sexual ethics separately. They believe that it is one thing to define a sexual phenomenon (such as rape or adultery) and quite another thing to evaluate it. Other philosophers of sexuality believe that a robust distinction between defining a sexual phenomenon and arriving at moral evaluations of it cannot be made, that analyses of sexual concepts and moral evaluations of sexual acts influence each other. Whether there actually is a tidy distinction between values and morals, on the one hand, and natural, social, or conceptual facts, on the other hand, is one of those fascinating, endlessly debated issues in philosophy, and is not limited to the philosophy of sexuality.
