 John Stuart Mill (1806–1873) defended a version of liberal utilitarianism, but scholars disagree about what kind of utilitarianism that was. We can safely say that, as a utilitarian, Mill thought human conduct should promote the happiness or welfare of those affected. But was Mill an act-utilitarian, who thought that right acts are those that promote as much happiness as can be done on the particular occasion, given the alternatives available to the agent? Or was he a rule-utilitarian, who thought that right conduct was conduct permitted by rules that, when publicly known to be generally accepted or followed, would maximize happiness or welfare? Or was he a motive-utilitarian, who thought that one should act as the person with the motives or virtues most productive of happiness should act? (For a discussion of these interpretive questions, see the related entry on  Mill’s moral and political philosophy.)  Although this entry will steer clear of these interpretive hurdles and will concentrate on Mill’s discussion of the nature of happiness and of some of the institutional structures that can promote happiness, these questions of interpretation will be relevant to a final assessment of Mill in Section 4, below.