γαλήνη is "calm," the smooth surface of a windless sea; in Marcus it is a metaphor-name for the achieved calm of the soul, the positive state that supervenes when troublesome impressions have been wiped away. Unlike ἀταραξία (imperturbability, the absence of anxiety — with an Epicurean colouring) and TERMἀπάθεια (freedom from the passions — a technical Stoic concept), γαλήνη names not the absence of something but a positively felt clear stillness. It is kin to the image of the clear sky: if αἰθρία is the fair weather overhead, γαλήνη is the smooth water beneath the keel. It is reached not by suppression but by withdrawing assent from the disturbing TERMimpression: remove the false judgement, and the sea calms of itself.

Med. 05-02 (wipe out the impression and be at once in perfect γαλήνη); 07-28 (γαλήνη from just action — the wake of virtue); 07-33 (the mind keeps its γαλήνη by ἀπόληψις — walling the pain off); 07-68 (the mind in γαλήνη even as beasts tear the flesh); 08-28 (the soul may keep its αἰθρία and γαλήνη, refusing to call pain an evil); 12.22 (γαλήνη and the "quiet anchorage" of the soul). The background: the image of the "calm sea" as an ideal state of the soul; cf. ἀταραξία in Epicurus and TERMεὔροια βίου in the Stoics. The fuller technique that leads to the calm is Med. 9.7 (ἐξάλειψον φαντασίαν).

In 05-02 γαλήνη is the goal of a one-line exercise of assent: "how easy" (εὔκολον) it is to wipe out the disturbing TERMimpression and be at once in perfect calm. The word is emphatically maritime and positive: not "non-anxiety" but a smooth surface.