Justice is one of the four cardinal virtues of the Stoic system (alongside φρόνησις — practical wisdom, ἀνδρεία — courage, σωφροσύνη — temperance). Chrysippus defined δικαιοσύνη as ἐπιστήμη ἀπονεμητικὴ τῆς ἀξίας ἑκάστῳ — "the knowledge of how to distribute to each what he deserves." In the Stoic system it is not one of four "separate" virtues but an aspect of the single virtue, the aspect specifically tied to the social nature of the human being: justice is the manner in which practical reason is realised in social relations.

SVF III 262–294 (the doctrine of the four virtues); III 264 (the definition of δικαιοσύνη); DL VII 92–94; Stob. Ecl. II 59–60 W; LS 61. The Platonic background: Resp. IV 433a–434c. Aristotle: Eth. Nic. V in its entirety. In Marcus the form δικαιότης (a contraction of δικαιοσύνη) at Med. 2.5; 3.6; 09-31 (δικαιότης in what is "from your own cause": justice as the discipline of action); 10.11; 12.15. The full form δικαιοσύνη — 05-12 (among the true goods is δικαιοσύνη, against the seeming goods of the many); 05-34 (the good lies in a just disposition and action, ἐν διαθέσει δικαίᾳ); 06-47 (to live μετ’ ἀληθείας καὶ δικαιοσύνης, benevolent even to liars); 06-50 (to act when ὁ τῆς δικαιοσύνης λόγος leads); 07-54 (κατὰ δικαιοσύνην toward the people at hand — the second member of the triad); 07-63 (souls are deprived of δικαιοσύνη too against their will — hence gentleness); 08-39 (δικαιοσύνη has no counter-virtue in the rational constitution — there is no "too much" of it).

In 02-05 δικαιότης rounds off the quartet of virtue-tonalities in which one is to act: σεμνότης (dignity), φιλοστοργία (natural affection), ἐλευθερία (freedom), δικαιότης (justice). The inclusion of justice is a structural turn: virtuous action in Marcus is inseparable from "social rightness." Cf. Med. 11.10 — the famous formula: "δικαιοσύνη is not one of the virtues; it is virtue in its social dimension; all the rest (courage, temperance, prudence) are its preconditions." Related to DOGMAoikeiosis (the ontological ground of social ethics) and TERMsynergia (its active expression).