Axia literally means "worth," "what something is worth." It is the Stoic technical term for the value of indifferent things (TERMadiaphora) — the intermediate scale that lets the Stoic act rationally in the world without converting an indifferent into a good or an evil.

The Stoic structure of value is three-tiered:

Within the TERMindifferents, axia distinguishes:

• προηγμένα (preferred) — what has positive axia: health, strength, beauty, ability, friends, property sufficient for a virtuous life. These are naturally to be pursued.
• ἀποπροηγμένα (dispreferred) — what has negative axia (apaxia): illness, mutilation, disgrace, poverty. These are naturally to be avoided.
• οὐδέτερα — strictly "without axia," neutral: odd/even, the length of a hair.

Chrysippus gives the formula: τὰ μὲν προηγμένα τὴν ἀξίαν ἔχει, τὰ δὲ ἀποπροηγμένα τὴν ἀπαξίαν — "the preferred have axia, the dispreferred have apaxia" (DL VII 105).

The crucial point: axia does not turn a thing into a good. Health has high positive axia, but is not ἀγαθόν. The implication: I rationally prefer health to illness (I choose the remedy, I avoid danger), but I am not distressed by illness, because it is not a genuine evil. Axia regulates action; virtue regulates the state of the soul.

SVF III 124–139 (Chrysippus on axia); DL VII 105–107 (the classical exposition); Stob. Ecl. II 79–85 W; Cic. De fin. III 50–52 (Cato on προηγμένα and axia; the Latinisation aestimatio); LS 58 ("Value and indifferents"). Polemic: Plut. De Stoic. rep. 1048a–c (on the fine distinctions as contradictory). In Marcus axia is not central as a term (he works mainly with TERMἀδιάφορα), but it does appear: Med. 3.6 ("nothing ought to be valued above…"); 4.20.

The Stoic doctrine of axia is a fine piece of engineering that resolves a paradox. Without it the Stoics would be apologists for total apathy: "everything external is indifferent, so do whatever you like." With it: "everything external is indifferent in respect of good/evil status, but is differentiable in respect of axia for the purposes of rational action."

This structure enables the Stoic to be active in the world: to treat wounds, secure food, defend the state, help friends. All these actions are rational because they are directed at proēgmena (health, safety, well-being, friendship). But the sage never depends on their attainment — if the actions fail, he does not suffer (suffering would be a false πάθος born from a false evaluative assent).

Cicero's Latinisation aestimatio (whence French estime, German Schätzung, English esteem) had a large part in shaping the European vocabulary of evaluation. The idea of "value distinct from the good" passes through the Stoics → the schoolmen and enters the modern era, where it is discussed in Kant (Wert / Würde, value and dignity), in Nietzsche (Umwertung aller Werte), and in the phenomenologists (Scheler).

See also:

• TERMτιμή — "honour, price" — a kindred term in the same semantic field, but narrower (social recognition).
• TERMadiaphora — the category within which axia makes its distinctions.
• the self-sufficiency of virtue — the doctrine that rests on the distinction between the good and axia.