A Theory of Justice (1971), by John Rawls, is "one of the most influential works in moral and political philosophy written in the twentieth century," according to Samuel Freeman in the Collected Papers of John Rawls (1999).

A Theory of Justiceis Rawls's attempt to formulate a philosophy of justice and a theoretical program for establishing political structures designed to preserve social justice and individual liberty. Rawls writes in reaction to the then predominant theory of utilitarianism, which posits that justice is defined by that which provides the greatest good for the greatest number of people. Rawls proposes a theoretical person who, shrouded in a veil of ignorance, must design a just society without foreknowledge of his or her own status in that society. Rawls asserts that from this objective vantage point, which he calls the original position, the individual will choose a system of justice that adequately provides for those positioned on the lowest rungs of society. The individual will do so because he or she may end up in such a disadvantaged position and will want to be adequately provided for. Rawls draws from earlier theories of political philosophy that posit a social contract by which individuals implicitly agree to the terms on which they are governed in any society. Rawls concludes that such a social contract, formulated from the perspective of the original position, will guarantee a just society without sacrificing the happiness or liberty of any one individual.

Rawls addresses issues of liberty, social equality, democracy, and the conflict of interests between the individual and society.