In A Theory of Justice, John Rawls writes that his theory of justice as fairness is contractarian and specifically builds on the social contract theory of Locke, Rousseau, and Kant.

Although Kant is less concerned with political thought than the other philosophers mentioned, he is clear that the most reasonable foundation for government is that the law should reflect a national collective will. The social contract is only a contract in the vaguest terms, since the individual citizen has no choice as to whether to agree to it or not. Nonetheless, Kant believes that any good law must be of the type that the reasonable citizen would approve if given the chance.

Rawls agrees with this and concentrates on refining the idea of the reasonable citizen. His famous "veil of ignorance" is a Kantian idea in that it equates reason with ethical integrity. There is nothing unreasonable in self-interest as a basis for personal decisions that principally affect oneself, but Rawls wants to abolish it as a factor in making decisions for a whole society.

In this way, his view of a just law follows that of Kant, who insists that the law reflects collective will, not individual will. It follows that any reasonable citizen taken at random should approve of the law, not only a citizen who belongs to a specially privileged group.