That consent often makes a serious normative difference is a non-negotiable feature of our common-sensical moral views, for “consent turns a rape into love-making, a kidnapping into a Sunday drive, a battery into a football tackle, a theft into a gift, and a trespass into a dinner party.” (Hurd 1996). And yet, a host of problems make giving a theoretical account of the role of consent harder than perhaps expected. Such problems become especially serious for liberalism – where consent seems especially significant, because of the central role of the value of autonomy in the liberal tradition. A central way of allowing people to be partial authors of their life stories is to require that certain things cannot be done to them without their consent. And unsurprisingly, liberals have been heavily relying on the role of consent – in personal interactions, and often also in justifying the legitimacy of the state. If the moral role of consent can be challenged, then, this is a huge problem for liberalism.

And indeed, the status of consent has been challenged, and with good reason. For starters, merely uttering the words “I hereby consent” is neither necessary nor sufficient for operating “the magic of consent” (Hurd 1996). Consent – fully normatively valid consent – may, of course, be given implicitly or tacitly. And according to some – though this is much more controversial – even hypothetical consent (consent that would have been given under some hypothetical conditions but that is not actually given) can sometimes do the work actual consent can do (Stark 2000, Enoch 2017). More importantly, explicitly consenting is not sufficient for valid consent either. There are many ways in which consent may be flawed, ways that render it less than fully normatively valid. So liberals must face up to the challenge of offering an understanding of flawed consent that will still leave sufficient room for consent to play its non-negotiable normative role.

The theoretical challenge here, then, is to give an account of how and why consent matters, in a way that will simultaneously respect the underlying (liberal-friendly) non-negotiable intuitions about consent mattering, but also accommodate the fact that consent is neither sufficient nor necessary for the normative effects of consent to materialize.