Chapter 4 evaluates Kantian ethics of sex, considering both Kant’s original framework and the revised interpretations of Allen Wood and Helga Varden. Kant’s traditional views, alongside classical natural law, are uniquely capable of explaining most commonsense sexual prohibitions—however, only because it seems he borrowed from natural law when it comes to the bedroom. To this he added rigid concerns about objectification and violation of the Formula of Humanity that implies a prudish obligation that couples minimize sex. Kant thus cannot account for the goodness of spousal sexuality. Wood and Varden propose a different natural purpose for sex, allowing far greater sexual liberty than Kant—or common sense, for that matter—could accept.