Time is a river of becoming (ποταμὸς τῶν γινομένων) and a violent stream (ῥεῦμα βίαιον): no sooner is a thing seen than it is swept past, another rushes into its place, and it too will be carried off. Nothing abides. The image renders the radical transience of all things — the Heraclitean flux (Heraclitus, DK B12) applied to time. The river's waters are the events themselves, τὰ γινόμενα; αἰών here is not "eternity" but time-as-age, a ceaseless flow.

The therapeutic point: since all is but water flowing by, it is senseless to cling to the passing or to dread its loss (cf. 06-15 — "in this flowing stream, where nothing is stable, what is there to prize?"). Only the present TERM"now" is real, and that but for a moment; and it alone can be lost (2.14).

04-43 — the image in pure form. The cognate series of flux / transience:

• Med. 05-23 — the substance of things like a river in perpetual flow, nothing stands still;
• Med. 06-15 — some things hurrying into being, others out of it; in the stream nothing is stable;
• Med. 07-19 — all bodies sweep through the universal substance "as through a rushing torrent" (χείμαρρος); eternity has "swallowed down" the Chrysippuses and Socrateses;
• Med. 2.17 — the substance flowing, all impermanent;
• Med. 4.46 — Marcus quotes Heraclitus directly (the death of earth is to become water, and so on).

On the present: Med. 2.14 — one can lose only the current "now" (TERMparon).

In 04-43 the image serves the discipline of desire through the contemplation of nature (φυσιολογία): reconciliation with the flow and non-attachment to the passing (DOGMAamor-fati). Logically it stands beside the other images of TERMchange / flux, but with a distinctive stress on non-abiding: unlike the seed-image (everything-is-seed, where the stress is on generative productivity) and the image of the one living cosmos (04-40, where the stress is on coordination), here it falls on the ceaseless sweeping-away of all things.