 Even in its confined role, however, consent has attracted powerful criticism. (For a good survey see Simmons 1979: 57–100; for a qualified defence see Beran 1987.) Much of it has focused on the questions of whether consent is in fact given and, if given, whether it would bind. The first thing to notice is that here consent is meant to be a performative commitment that undertakes an obligation through the very act of consenting. Thus, it is closer to how we normally understand the notion of a promise, rather than to how consent is used in other contexts. (When you consent to surgery, for example, you don’t incur an obligation to undergo surgery. You simply waive your objection to undergoing surgery.) Like other promises and oaths, however, there are limits to the validity of consent. Not only because consent is invalid if secured via coercion, manipulation or duress, but also because there are things we lack the moral power to consent to. Locke, for example, argues that one can consent neither to be killed nor to slavery, and thus not to anything tantamount to slavery, including absolute government. One can imagine a similar argument to the conclusion that political consent must be revocable. But as we build in all these validity conditions, the commitment itself seems to be doing less and less work, leading some to conclude it becomes “essentially irrelevant” (Pitkin 1965 [1972: 57]). Consent is saved from irrelevance only if we can explain why we also value a power to bind ourselves to obey. David Hume could conceive no reason at all: promise-keeping is an “artificial virtue” serving the public good, just like obedience to law. So long as law is tolerably legitimate—and Hume is prepared to give it a very wide berth—a promise to obey is redundant, for any plausible answer to the question of why we are bound by the promise would “immediately, without any circuit, have accounted for our obligation to allegiance”; “being of like force and authority, we gain nothing by resolving the one into the other” (Hume 1748 [1985: 481]).