The emerald formula. A maxim with a mirror structure: the human "whatever anyone does or says — TERMI must be ἀγαθός" is repeated in the voice of the stone: "…I must be emerald and keep my own colour" (τὸ ἐμαυτοῦ χρῶμα ἔχειν). The argument is from the nature of the thing: the emerald's colour is not a reaction to its surroundings but its own quality; other people's words and deeds do not enter the stone's constitution. So goodness (ἀγαθόν) is not a response to others' behaviour but my colour: the one thing "whatever anyone does" cannot touch — cf. the DOGMAdichotomy at 5.25 ("another sins — his affair; I keep my own disposition") and 9.20 (another's wrong must be left where it arose).

The row of standards: gold, emerald, purple. Three objects of unconditional value in the ancient world — and all three valuable in themselves, not by recognition: the direct pair is 4.20, which says literally: "does the little emerald become worse if it is not praised?" (τί γὰρ χεῖρον γίνεται σμαράγδιον ἑαυτοῦ, ἐὰν μὴ ἐπαινῆται;). There the stone argued against the thirst for praise; here — against infection by another's badness: two faces of the same autarky of the good. The inverse image is the soul dyed by its thoughts (5.16: the soul is "steeped" in its impressions; 6.30: "see that you are not Caesarified, not dyed purple"): the soul, unlike the stone, can be dyed — which is why keeping one's own colour is for it not a given but a task. Note the irony of the series: πορφύρα — the imperial dye — stands in one row with the stones as something that must keep its own colour rather than recolour its wearer.

A maxim for repetition. τοῦτο ἀεὶ ἔλεγεν — the stone "would always be saying this": the formula is built as a πρόχειρον to be repeated at every collision with another's baseness. The governing discipline is action (to remain good in the deed); the sustaining one, assent (not to take another's evil as a reason to betray oneself).