Bargaining and the impartiality of the social contract

The question of what a group of rational agents would agree on were they to deliberate on how to organise society is central to all hypothetical social contract theories. If morality is to be based on a social contract, we need to know the terms of this contract. One type of social contract theory, contractarianism, aims to derive morality from rationality alone. Contractarians need to show, amongst other things, that rational and self-interested individuals would agree on an impartial division of a cooperative surplus. But it is often claimed that contractarians cannot show this without introducing moral assumptions. This paper argues that on the right understanding of the question contractarians are asking, these worries can be answered. Without relying on moral assumptions, the paper offers a novel derivation of symmetry, which is the axiom responsible for the impartiality of the most famous economic bargaining solutions appealed to by contractarians.