The relation of Reciprocity to Justice has been stated already. [4]
But we must not forget that the subject of our investigation is at once Justice in the absolute sense and Political Justice. Political Justice means justice as between free and （actually or proportionately） equal persons, living a common life for the purpose of satisfying their needs. Hence between people not free and equal political justice cannot exist, but only a sort of justice in a metaphorical sense. For justice can only exist between those whose mutual relations are regulated by law, and law exists among those between whom there is a possibility of injustice, for the administration of the law means the discrimination of what is just and what is unjust. Persons therefore between whom injustice can exist can act unjustly towards each other （although unjust action does not necessarily involve injustice）: to act unjustly meaning to assign oneself too large a share of things generally good and too small a share of things generally evil. [5] This is why we do not permit a man to rule, but the law, because a man rules in his own interest,