This chapter aims to give an account of social science’s various contributions to the issue of the different levels of social justice. More specifically, we analyse the ways social justice is applied at each of the (micro, mezzo and macro) social levels. One of the main difficulties the empirical social sciences need to overcome is how they observe or even measure how the moral principles and prevailing ideals arising from moral and political philosophy are concretely embodied in levels and areas where they interact and are disputed within particular groups and in the daily lives of individuals. This distance between the moral norm that is thought to float outside the social world and the numerous more or less developed and more or less contradictory concrete judgements we express every day and that frame our actions in a more or less reflective way raises the question of the levels or degrees of understanding of social justice, if only as a way of appreciating the diversity and complexity that have developed within this field of research in recent decades.