Genre and place in the book. The fifteenth passage is a short gnomic fragment — one of the most obscure in the whole book — on moral perception. After the exhortation to urgency (03-14), a cryptic note: people (Οὐκ ἴσασι — "they do not know") do not grasp how many things common action-words signify; and "seeing what ought to be done" (τὰ πρακτέα) is accomplished not by the bodily eyes but by "another kind of vision" (ἑτέρᾳ τινὶ ὄψει) — the inner eye of moral judgement.

Textual caveat. The connection of the verb-list to the "other vision" is disputed, and the passage is elliptical; some editors suspect compression or corruption. The reading below is therefore given as the most probable, not as certain.

Structure.

1. Οὐκ ἴσασι, πόσα σημαίνει — "they do not know how many things are signified by" — the verbs: τὸ κλέπτειν (stealing), τὸ σπείρειν (sowing), τὸ ὠνεῖσθαι (buying), τὸ ἡσυχάζειν (keeping quiet / staying still), τὸ ὁρᾶν τὰ πρακτέα (seeing what is to be done).
2. ὃ οὐκ ὀφθαλμοῖς γίνεται ἀλλ’ ἑτέρᾳ τινὶ ὄψει — "which is done not by the eyes but by another kind of vision."

Key analyses.

• The polysemy of action-words (πόσα σημαίνει). The probable sense: ordinary words for actions carry many significations; one and the same outward act (theft? sowing? buying? inaction?) can be morally very different things, and which signification is morally relevant — "what ought to be done" — is grasped not by literal sight but by moral insight.
• τὰ πρακτέα — "the things to be done." Conceptually near καθῆκον (the appropriate act, "the fitting"), but the word here is πρακτέα (the verbal adjective of πράσσω), not καθῆκον; hence the link to kathekon is thematic, not lexical.
• ἑτέρα ὄψις — "another kind of vision." The inner eye, the eye of the mind/soul. Moral discernment sees what the bodily eyes do not: the moral quality of an act, the thing that should be done. This is the faculty of judgement (judgement / the ruling part / intellect) "seeing" rightly — though Marcus names it only obliquely ("another sight"). The metaphor of the soul's eye is Platonic (Rep. VII, the eye of the soul turned toward the Good) and Stoic.
• The verb-list. Possibly: even mundane acts (stealing, sowing, buying, keeping still) are polysemous; only the "other vision" discerns what each is morally. (The reading of the list is uncertain — see the caveat above.)

The disciplines. The leading one is assent: moral discernment, the "other vision" that judges/perceives rightly, beyond the senses (the correct valuation of what a thing is and what is to be done). The secondary is action: τὰ πρακτέα, the appropriate deeds that this vision discerns.

Stylistics. Extreme brevity and ellipsis (a gnomic fragment). The asyndetic list of verbs (κλέπτειν, σπείρειν, ὠνεῖσθαι, ἡσυχάζειν). The arresting close — "another kind of vision" (ἑτέρᾳ τινὶ ὄψει). The contrast of the bodily eyes with the sight of the soul.

Parallels. The eye of the soul / inner vision — Plato Rep. 518c–519b (the eye of the soul turned toward the Good). The discernment of the fitting (καθήκοντα / τὰ πρακτέα) — DL VII 107–108; kathekon.