Justice is the name for a human characteristic that everyone feels spontaneously: what is fair or unfair in a social relationship. Animals do not have justice. The human reason (logos – λόγος) acts in order to reveal what is included in justice. Thus, as a participation in justice, the human conscience (logos) finds the law. Away from modern (and current) theories of natural law that sets rules either to be applied directly to social reality or to be individual powers to be opposed to positive law, the classical theory of law is a social quest directed toward doing the right thing. In the wake of Aristotle, classical natural law is a methodology (based on dialectics) to find justice in society. The etymology of dialectics, dia-lektos, teaches us that it signifies the exchange of words between different interlocutors. In this sense, dialectics is practiced every day by those gathering together, who receive advice relating to a given situation. Dialectic does not solely aim to persuade; but also tries to look for the natural law. Legal conclusions, notwithstanding the authority submitting them, are ultimately questionable. Having been born in dialectic, these conclusions remain as such. Nonetheless, their very existence gives the natural law, a fragmented expression of justice. Unlike morality, or the precepts of divine law, natural law is not given at all: it must be established through dialectic. Morality retains a reduced role, broadly limited to the discovery of natural law’s essence, for example by prohibiting murder from being accepted in principle. Still, such a moral prescription does not solve the problem to know who is guilty of murder. As a methodology, classical natural law acknowledges the contingency of social norms with regard to the distribution of common goods. As a process that attends to the common good available and the merits of people understood in a broad fashion as encompassing the resources they possess, classical natural law cannot a priori determine what specific rights or goods particular specific people should have. Adapting to reality is necessary: a dialogue is always established to amend the contours of justice. For this purpose, classical natural law is the methodology for justice to achieve its new forms, to distinguish new data from the social distribution of goods and responsibilities. The protection of the worker, of the minor or of the foreigner is of indisputable moral value, though its implementation follows the oscillations of time. However, as a moral horizon, seeking justice involves a perennial effort to recognise other humans as human.