An influential view of sexual morality claims that participant consent is sufficient for the moral permissibility of a sexual act. I argue that the complex and frequently dark nature of sexual desire precludes this, because some sexual desire has a character such that it should not be gratified, even if this were consented to. I illustrate this with a discussion of a famous literary character, the Vicomte de Valmont, and draw on Kant's anthropology to illuminate the nature of such desire, (...) before offering an account of its psychological roots. In the course of the paper I explain why the view of sexual desire endorsed by my main opponents is mistaken, and attack the limited conception of the normative which is a central plank in the argument of a prominent recent defender of the view, Igor Primoratz. (shrink)