John Rawls’ use of a contractarian strategy for justifying basic principles of justice has raised the hope that a similar strategy might work for a theory of right and moral principles generally. I want to show that this hope cannot be fulfilled.

In what follows I interpret contractarianism in a Rawlsian way on the grounds that his is the most plausible version of the doctrine we are likely to get. I am not however concerned with the details of Rawls’ argument for justice but instead with an idea that appears to underlie the contractarian strategy. In order to avoid the complications of Rawlsian exegesis, I choose to discuss the doctrine as it might be used to justify a moral principle of mutual assistance and not as Rawls in fact uses it to justify principles of justice.