In this article I am concerned with reasoning about matters of justice. There is no doubt that justice-reasoning is a significant mode of ethical reasoning and its importance is therefore generally accepted. But there is a considerable debate concerning the role formal justice can play in reasoning about justice. In this paper, I first provide an analysis of formal justice. I then show that the concept of formal justice is identical to one notion of fairness and I illustrate the function (...) of formal justice in reasoning about issues of fairness. In the third section, I argue that formal justice is an essential component of justice tout court and I demonstrate its value for understanding and assessing reasoning about matters of justice. The overall result of this investigation is that formal justice is an important notion that has a special function in moral thinking, which has not been sufficiently appreciated in the literature. (shrink)