Normativity in Lewis' and Bicchieri's Accounts of Conventions and Norms

Lewis [3] argues that, generally, we ought to conform to con- ventions because that answers (1) our own preferences, and (2) the preferences of others. While (1) is based on instrumental rationality, (2) is based on a moral principle or norm: other things being equal, we should do what answers others’ preferences. Bicchieri [1] claims there is a third kind of normativity, neither rational nor moral, that applies to social norms. I argue that conventions draw their normativity from instrumental rationality and other independent moral principles or norms, and that it is unclear what further normativity could there be.