The ruling part is a clear, sweet spring (πηγὴ διαυγὴς καὶ γλυκεῖα) welling up with drinkable water. Let someone revile it, let him cast mud or dung into it — the spring "is in no way stained" (οὐδαμῶς βαφήσεται): it "quickly disperses and washes out" (διασκεδάσει καὶ ἐκκλύσει) what was thrown in and goes on pouring forth clear water. Outward abuse and filth cannot dye a living source — they are merely carried off by its current.

The key contrast is the spring versus the stagnant well (πηγὴ ἀέναος / φρέαρ): a living, self-renewing fount cannot be muddied, whereas standing water takes in whatever falls into it and grows turbid. The difference is not strength but motion: so long as the source flows, the filth does not settle. The condition of purity is therefore active: "to guard yourself every hour toward freedom — with kindliness, simplicity, and modesty."

Med. 08-51 — the image in pure form: a clear spring which, reviled and pelted with filth, "does not cease welling up" and "is nowhere stained"; the demarcating question — "when will you possess an ever-flowing spring (πηγὴ ἀέναος), and not a stagnant well (φρέαρ)?"

• Med. 07-59 — the kindred image: "dig within — within is the spring of good (ἔνδον ἡ πηγὴ τοῦ ἀγαθοῦ), which will not run dry if you keep digging." There the stress is on the depth and inexhaustibility of the source; here, on its imperviousness to pollution.

The image serves the DOGMAself-sufficiency of the ruling part (purity wells up from within, it is not applied from outside) and the DOGMAdichotomy (another's abuse and filth do not reach the water — "not my harm"). It is kindred to the TERMcalm (the smooth surface as rest) and to the mind-sphere (invulnerability). The difference from the sphere is real: the sphere is static perfection and invulnerability (nothing touches it); the spring is dynamic self-cleansing (it does not merely keep the filth out but carries and washes it away, renewing itself). The meaningful contrast is the stagnant well: the mind that lets the external (grievances, judgments) settle and go stale within it. The practical key is to keep the source in motion: the ceaseless "care for freedom."