  What are social conventions? A natural first thought is that they are explicit agreements, such as promises or contracts, enacted either by parties to the convention or by people suitably related to those parties (such as their ancestors). This conception underwrites at least one famous conventionalist account: Thomas Hobbes’s theory of government as resulting from a social contract, into which agents enter so as to leave the state of nature. However, it seems clear that the vast majority of interesting social phenomena, including government, involve no explicit historical act of agreement. Social conventions can arise and persist without overt convening.