Is Consensual Non-Monogamy Ethical?

Traditionally, monogamy has been the dominant form of romantic relationships, but today, more and more people practice consensual non-monogamy, including open relationships and polyamory. Proponents of such formats also call them “ethical non-monogamy”. This article critically examines the moral permissibility of non-monogamous relationships. It first offers a liberal argument for traditional sexual ethics, which views romantic love as a necessary condition for the moral permissibility of sexual relations. This argument is based on the liberal principle, dating back to Immanuel Kant, that a person should not be used as a mere means or instrument. Only in loving sex do people not use their partners as instruments for their own pleasure. It then offers an evolutionary argument for modal monogamy, that is, the thesis that romantic love can only be monogamous. It concludes that only in monogamous relationships can people treat each other with due respect. Paradoxically, it is monogamy that best advances feminist goals and serves as the most progressive and emancipatory moral framework for sexual relations.