The duality of the concept of justice is considered. There are two kinds of justice: Hierarchical justice and Equal justice. The processes, emergence and boundaries of justice are defined. It is shown that the instinct of self-preservation created conditions for the emergence of Hierarchical Justice. Reason is necessary for the emergence of Justice of Equality. Conclusion: Just relations are a compensation for obedience to the strong or to the rules of society. Power is a product of the development of Hierarchical Justice. Democracy is a compensation for the loss of rights by the possibility to choose the rulers. The product of the development of Justice of Equality is specialization and functionality in society, dissemination of knowledge and experience. The framework of behavior set by the requirement of Equality Justice created the transformation of competition from opposition to the desire to act more effectively. The positive and negative manifestations of Equity are examined. The emergence of harmony in society, based on the harmony of the interaction of fairnesses, is described. The emergence of contradictions between morality and law is explained. It is shown that Equality Justice evolutionarily displaces Hierarchy Justice, but will not achieve complete superiority.Key words: justice, hierarchy, equality, self-preservation instinct, reason, efficiency, compensation