In John Rawls's A Theory of Justice, he offers an imaginative scenario in which people would have the opportunity to create a just society that they would have to live under. They would be, Rawls says, shrouded in a "veil of ignorance" about the role they would play in society. He claims that if people were actually put in this scenario, the rational choice would be to provide for one's own support should one wind up at the lower rather than the higher end of the social spectrum. By presenting this thought experiment, Rawls wants to show what type of society has a rational foundation:
Just as each person must decide by rational reflection what constitutes his good, that is, the system of ends that it is rational for him to pursue, so a group of persons must decide once and for all what is...just and unjust. The choice which rational men would make in this hypothetical situation of equal liberty...determines the principle of justice.
In this way, the "veil of ignorance" would lead to a justice that was founded on two essential principles. First, it would be a justice founded on individual liberty. Second, it would allow for a society where the least fortunate people were cared for by the rest of society. These principles were often held to be mutually exclusive, and by creating a thought experiment based on a "veil of ignorance," Rawls asserted that he had shown a way to reconcile them theoretically.