 John Rawls’ theory of justice is the most widely-cited example of a contractarian theory, but before outlining it, two words of caution are necessary. First, the shape of the theory has evolved from its first incarnation in Rawls (1958) through his major work A Theory of Justice (Rawls 1971) and on to Rawls (1993) and Rawls (2001). Second, although Rawls has consistently claimed that the principles of justice he defends are the principles that would be selected by people in a suitably designed ‘original position’ in which they are asked to choose the social and political institutions they will live under – this is what qualifies his theory as contractarian – it is less clear how important a role the contract itself plays in his thinking. His principles, which are discussed elsewhere (see the entry on  John Rawls),  can be defended on their own merits as a theory of social justice for a modern liberal society, even if their contractual grounding proves to be unsound. Rawls presents the contracting parties as seeking to advance their own interests as they decide which principles to favour, but under two informational constraints. First, they are not allowed to know their own ‘conception of the good’ – what ends they personally find it most valuable to pursue – so the principles must be couched in terms of ‘primary goods’, understood as goods that it is better to have more rather than less of whatever conception of the good you favour. Second, they are placed behind a ‘veil of ignorance’ that deprives them of any knowledge of personal characteristics, such as their gender, their place in society, or the talents and skills they possess. This means that they have no basis on which to bargain for advantage, and have to consider themselves as generic persons who might be male or female, talented or untalented, and so forth. In consequence, Rawls argues, all will choose to live under impartial principles that work to no-one’s advantage in particular.