It is important to study religion and ethics in conjunction with human sexuality because they frequently provide the framework within which people judge the rightness or wrongness of sexual activity. They give rise to attitudes that influence the way members of a society regard sexuality, and they are therefore powerful influences on behavior. Religion and ethics may be hedonistic (pleasure oriented) or ascetic (emphasizing self-discipline). They may be legalistic (operating by rules) or situational (making decisions in concrete situations, with few rules).

In the great ethical traditions, ancient Judaism had a positive, though legalistic, view of sexuality. Christian sources are ambivalent about sexuality, with Jesus saying little on the subject and with St. Paul, influenced by the immorality of Roman culture and his expectation of the end of the world, being somewhat negative. Later, Christianity became much more ascetic, as reflected in the writings of Augustine and Thomas Aquinas, who placed Catholic moral theology in the natural-law mold. The Protestant Reformation abolished clerical celibacy and opened the door to greater individual freedom in ethics. Today, new biblical scholarship has led to a wide variety of positions on issues of sexual ethics.

Humanistic ethics rejects external authority, replacing it with a person-centered approach to ethics. A variety of approaches to sexuality can be found in Islam, Hinduism, and Buddhism.

Six ethical issues involving human sexuality have provoked lively debate recently. Although the Western ethical tradition opposes sex outside marriage, some liberals are open to sex among the unmarried, under certain conditions. Contraception is opposed by Roman Catholicism and Orthodox Judaism on scriptural and natural-law grounds, but it is valued positively by other groups. Abortion provokes a very emotional argument, with positions ranging from condemnation on the grounds that it is murder to a view that asserts the moral right of women to control their own bodies. Although the traditional view condemns homosexuality absolutely, there is some movement toward either a qualified approval of at least civil rights for gay people or a more complete acceptance of their lifestyle. The spread of AIDS poses serious ethical problems, which involve a balancing of individual needs with the welfare of society. Developments in the technology of human reproduction are creating complex ethical issues with few clear norms.

A possible resolution of the conflict between the Old Morality and the New Morality involves an ethics of human sexuality, neither hedonistic nor rigidly ascetic, which takes seriously the historical tradition of ethical thinking while insisting that decisions be made on the basis of the specific situation.