The following passage is adapted from a journal article. 

To understand John Rawls's theory of justice, one first needs to grasp what he was reacting against. The dominant approach in pre-Rawls political philosophy was utilitarianism, which emphasized maximizing the fulfillment of people's preferences. At first sight, utilitarianism seems plausible—what else should we do but try to achieve the most satisfaction possible for the greatest number of people?—but the theory has some odd consequences. Suppose executing an innocent person will appease a mob, and that doing so will therefore increase total satisfaction. Incredibly, a utilitarian would have to endorse the execution. Rawls accordingly complains that, in the utilitarian view, there is no reason "why the violation of the liberty of a few might not be made right by the greater good shared by many."

If we reject utilitarianism and its view about the aim of the good life, how can we know what justice requires? Rawls offers an ingenious answer. He asserts that even if people do not agree on the aim of the good life, they can accept a fair procedure for settling what the principles of justice should be. This is key to Rawls's theory: Whatever arises from a fair procedure is just.

But what is a fair procedure? Rawls again has a clever approach, beginning with his famous veil of ignorance. Suppose five children have to divide a cake among themselves. One child cuts the cake but does not know who will get which shares. The child is likely to divide the cake into equal shares to avoid the possibility of receiving the smallest share, an arrangement that the others will also admit to be fair. By denying the child information that would bias the result, a fair outcome can be achieved.

Rawls generalizes the point of this example of the veil of ignorance. His thought experiment features a situation, which he calls the original position, in which people are self-interested but do not know their own station in life, abilities, tastes, or even gender. Under the limits of this ignorance, individuals motivated by self-interest endeavor to arrive at a solution in which they will not lose, because nobody loses. The result will be a just arrangement.

Rawls thinks that people, regardless of their plan of life, want certain "primary goods." These include rights and liberties, powers and opportunities, and income and wealth. Without these primary goods, people cannot accomplish their goals, whatever they may be. Hence, any individual in the original position will agree that everyone should get at least a minimum amount of these primary goods. Unfortunately, this is an inherently redistributionist idea, since the primary goods are not natural properties of human beings. If someone lacks a primary good, it must be provided, at the expense of others if necessary.