The Stoic moral system rests on four cardinal virtues: wisdom (sophia), courage (andreia), justice (dikaiosune), and temperance (sophrosune). Wisdom is the capacity to judge what is truly good, bad, or indifferent; it is the foundation because every other virtue depends on correct judgment. Courage is persistence in pursuing the good despite fear or hardship. Justice is treating others with fairness and kindness and recognizing one's social obligations. Temperance is self-discipline over pleasures, appetites, and passions. Justice in particular reflects the Stoic belief that human beings share a common rationality and are therefore fellow citizens of a single cosmic polity, a doctrine called cosmopolitanism, expressed through the related view of sympatheia, the sense that all things are interconnected and mutually responsive.
Underpinning this ethics is the Stoic doctrine of logos, the rational principle that orders the cosmos. Humans participate in this logos through reason, and to "live according to nature" is to live in harmony with both rational human nature and the broader order of the universe. Stoics distinguished sharply between pathē, the destructive passions that arise from false judgments, and eupatheiai, the rational healthy emotions that arise from correct ones. The three eupatheiai are joy (chara), which replaces base pleasure; caution (eulabeia), which replaces base fear; and rational wishing (boulēsis), which replaces base appetite. The goal is apatheia, often mistranslated as apathy but really meaning freedom from being ruled by reactive passions, not absence of feeling.
External things like health, wealth, reputation, illness, poverty, and dishonor are classified as indifferents: they are not good or bad in themselves, though some are preferred when they do not compromise virtue. An appropriate action (kathēkon) is one consistent with one's nature and role; a perfect action (katorthōma) is the same action performed with full virtue, for the right reason in the right way. A settled steadiness of mind through both good and bad fortune, ataraxia, is what Stoics aimed for, and they shared this goal with Epicureans, though they reached it by very different paths. Marcus Aurelius called this inner freedom the inner citadel, the inviolable mental space where no external can reach without your permission.