What we generally mean by justice is actually fairness. We live in a society where order is held by common rules and standards; and as a result, trust, trade and co-operation are facilitated for the benefit of the majority. Fairness lies at the core of these rules–it is a natural instinct that helps us divide benefits in a way that keeps the majority happy…a sense for what’s “right”.
Justice isn’t fairness–it’s the enforcement of fairness, be that within or without the law. It’s not a thing in itself but rather something that one does. Furthermore, justice is only desired by the weak. The strong take by breaking the unwritten rules of fairness. If the strong are harmed, they will seek retribution for it is within their means to do so. If the weak are harmed, they will seek retribution through justice for direct retribution is inaccessible to them. Justice is what protects the weak from the strong through the enforcement of fairness.