A Theory of Justice is a work of political philosophy and ethics by John Rawls. It was originally published in 1971 and revised in both 1975 (for the translated editions) and 1999. In A Theory of Justice, Rawls attempts to solve the problem of distributive justice (the socially just distribution of goods in a society) by utilising a variant of the familiar device of the social contract. The resultant theory is known as "Justice as Fairness", from which Rawls derives his two principles of justice: the liberty principle and the difference principle.