Abstract In a democratic nation state with a relatively open economy, does the state have an obligation to seek to achieve equality among its citizens? If so, where does that obligation come from? And equality of what? I argue that the luck egalitarian conception of equality of opportunity, which requires the state to compensate for contingencies for which individuals are not responsible but not for those for which they are, is incompatible with the practical functioning and moral underpinning of a market economy. I discuss two views which focus on equality in social, political and economic relationships between individuals—Anderson’s conception of relational equality and my economic conception of mutual benefit. These approaches have a similar contractual or contractarian structure: they work from the several viewpoints of potential participants in cooperative ventures rather than the synoptic viewpoint of a moral spectator. They provide complementary justifications for social insurance.