The central idea of this paper is to identify the principal characteristics of a just society according to Rawls' vision. This way, we try to show how the principles of justice constitutes a mediation between certain conception of society and her basic structure. The idea from which Rawls organizes justice as equity is the idea of society as a system of social cooperation among free and equal people. This conception of person that Rawls handles is fundamental. Free and equal persons cannot accept utilitarianism that justifies that the well-being of the majority is more important than the freedom of a group of person. Utilitarianism as philosophical theory is unable to build the institutions of a democratic society. In consequence, justice as equity, which expresses across two principles of justice, appears as a more viable alternative. The first principle is the principle of equal freedom and the second principle recognizes the social and economic inequalities, but the former says in what moment they can be well-taken: they must couple with the principle of just equality of opportunities and the principle of difference. These principles are designed principally for the basic structure of society. Having said this, a just society is a society that has a just basic structure.