  This concept is the target of David Lewis’s celebrated analysis in Convention (1969). A social convention is a regularity widely observed by some group of agents. But not every regularity is a convention. We all eat, sleep, and breathe, yet these are not conventions. In contrast, the fact that everyone in the United States drives on the right side of the road rather than the left is a convention. We also abide by conventions of etiquette, dress, eating, and so on.