Rawls

If men’s inclination to self-interest makes their vigilance against one another necessary, their public sense of justice makes their secure association together possible. Among individuals with disparate aims and purposes a shared conception of justice establishes the bonds of civic friendship; the general desire for justice limits the pursuit of other ends. One may think of a public conception of justice as constituting the fundamental charter of a well-ordered human association. Existing societies are of course seldom well-ordered in this sense, for what is just and unjust is usually in dispute. Men disagree about which principles should define the basic terms of their association. Yet we may still say, despite this disagreement, that they each have a conception of justice. That is, they understand the need for, and they are prepared to affirm, a characteristic set of principles for assigning basic rights and duties and for determining what they take to be the proper distribution of the benefits and burdens of social cooperation.