There is an ongoing debate about the “ontology” of consent. Some argue that it is a mental act, some that it is a “hybrid” of a mental act plus behaviour that signifies that act; others argue that consent is a performative, akin to promising or commanding. Here it is argued that all these views are mistaken—though some more so than others. We begin with the question whether a normatively efficacious act of consent can be completed in the mind alone. Standard objections to this “mentalist” account of consent can be rebutted. Here we identify a much deeper problem for mentalism. Normatively transformative acts of consent change others’ reasons for acting in a distinctive—“robust”—way. Robust reason-changing involves acts aimed at fulfilling a distinctive kind of reflexive and recognition-directed intention. Such acts cannot be coherently performed in the mind alone. Consent is not a mental act, but nor is it the signification of such an act. Acts of consent cannot be “completed” in the mind, and it is a mistake to view consent behaviour as making known a completed act of consent. The robust reason-changing account of consent developed here shares something with the performative theory, but is not saddled with a label whose home is philosophy of language. Certain kinds of performative utterance may change reasons robustly, but not all robust reason-changing involves or requires acts of speech, and consent can be effected by a wide range of behavioural acts.