Justice concerns itself with the proper ordering of things and people within a society. As a concept it has been subject to philosophical, legal, and theological reflection and debate throughout history. A number of important questions surrounding justice have been fiercely debated over the course of western history: What is justice? What does it demand of individuals and societies? What is the proper distribution of wealth and resources in society: equal, meritocratic, according to status, or some other arrangement? There are myriad possible answers to these questions from divergent perspectives on the political and philosophical spectrum.

According to most theories of justice, it is overwhelmingly important: John Rawls, for instance, claims that "Justice is the first virtue of social institutions, as truth is of systems of thought." Justice can be thought of as distinct from and more fundamental than benevolence, charity, mercy, generosity or compassion. Justice has traditionally been associated with concepts of fate, reincarnation or Divine Providence, i.e. with a life in accordance with the cosmic plan. The association of justice with fairness has thus been historically and culturally rare and is perhaps chiefly a modern innovation [in western societies]. for Muslims, it is one of the fundamental values prescribed by al-Qur'an, and termed by Ibn Khaldun in his rise and fall of civilizations as a value on which creation is based.

Studies at UCLA in 2008 have indicated that reactions to fairness are "wired" into the brain and that, "Fairness is activating the same part of the brain that responds to food in rats... This is consistent with the notion that being treated fairly satisfies a basic need". Research conducted in 2003 at Emory University, Georgia, involving Capuchin Monkeys demonstrated that other cooperative animals also possess such a sense and that "inequity aversion may not be uniquely human." indicating that ideas of fairness and justice may be instinctual in nature.

Utilitarianism is a form of consequentialism, where punishment is forward-looking. Justified by the ability to achieve future social benefits resulting in crime reduction, the moral worth of an action is determined by its outcome.

Retributive justice regulates proportionate response to crime proven by lawful evidence, so that punishment is justly imposed and considered as morally correct and fully deserved. The law of retaliation (lex talionis) is a military theory of retributive justice, which says that reciprocity should be equal to the wrong suffered; "life for life, wound for wound, stripe for stripe."

Restorative justice is concerned not so much with retribution and punishment as with (a) making the victim whole and (b) reintegrating the offender into society. This approach frequently brings an offender and a victim together, so that the offender can better understand the effect his/her offense had on the victim.

Distributive justice is directed at the proper allocation of things — wealth, power, reward, respect — between different people.

Oppressive Law exercises an authoritarian approach to legislation that is "totally unrelated to justice", a tyrannical interpretation of law is one in which the population lives under restriction from unlawful legislation.

Kira" is the death god who craves justice. By killing criminals using only a book which he/she may write names in.

Some theorists, such as the classical Greeks and Romans, conceive of justice as a virtue—a property of people, and only derivatively of their actions and the institutions they create. Others emphasize actions or institutions, and only derivatively the people who bring them about. The source of justice has variously been attributed to harmony, divine command, natural law, or human creation.