  Lewis (1969, pp. 97–100) anticipates such objections and attempts to forestall them. He argues that conventions will tend to become norms. Once a convention prevails in some population, any member of the population will recognize that others expect him to conform to it and that they prefer he do so. He will also recognize that conforming answers to his own preferences. It follow that he ought to conform, since, other things being equal, one ought to do what answers both to one’s own preferences and to those of other people. Moreover, if people see that he fails to conform, then they will tend to sanction him through punishment, reproach, or distrust, since they will see that he acts contrary both to his own preferences and to theirs. To some extent, this argument recalls Hume’s argument in the Treatise that conventions of property generate moral norms. Robert Sugden (1986/2004) develops the line of thought in more detail.