In sexual matters, the concept of consent has recently come to the forefront. The concept allows a distinction to be made, notably from a legal standpoint, between what is considered to be raped and what is not. It is however a concept that is difficult to define with any clarity; its boundaries are fuzzy and it is the subject of much controversy, particularly with regard to the issues of prostitution and sadomasochistic practices (BDSM) within the ethics of sexuality. The purpose of this article is to attempt to clarify the terms of the debate. It firstly questions the foundations of sexual consent by analysing the differences or the conceptual confusion between desire and will, based initially on a reading of the philosophers of the 17th century René Descartes and Baruch Spinoza, who have opposing ideas with regard to the position of desire relative to intellect in human beings, before moving on to the psychoanalyst Sigmund Freud, who introduces the idea of unconscious desire. The article then shows that the impossibility of absolute liberty, and therefore consent free of any constraint, leads certain feminist organisations to question individual consent, even when it has been clearly formulated, and to invoke against this the notion of human dignity in a transcending sense, inspired by Immanuel Kant, the German philosopher of the 18th century. This concept is examined and studied in cases of prostitution and sadomasochism (BDSM). The conceptual analysis ultimately reveals the metaphysical nature both of the individualistic approach of consent and of the Kant-inspired approach of human dignity.