Place in the book. The exercise of the contemplation of nature (φυσιολογία) in its "flux" facet: the classic image of the river-substance and the abyss of time. The discipline of desire (non-attachment to the transient).
The river of substance. "MOTIFSubstance (οὐσία) is like a river in a continual flow (ῥύσει)": TERMthe activities are in ceaseless changes (μεταβολαῖς), the causes "in myriad turns" (τροπαῖς), and hardly anything stands still (οὐδὲν ἑστώς). The Heraclitean flux (Heraclitus, DK B12) applied to all that is: every thing is only a temporary configuration in the stream.
The abyss of time. Close at hand lies "EXERCISEthe boundless abyss (ἀχανές) of past and future, in which all things disappear." A temporal "view from above": between the two abysses of non-being, every object of pride is a point, swept off in an instant. Only the "now" is real, and that but for a moment.
The therapy. Hence the conclusion: since all is carried off, and carried off quickly — "is he not a fool" (μωρός) who, amid this, is puffed up (φυσώμενος — pride), torn (σπώμενος — anxiety), or aggrieved (σχετλιάζων — complaint), "as though it were for long"? The irony of the close: it vexes him only "for a time, and a short time." Contemplating the flux dissolves attachment and gives rise to the DOGMAacceptance of the flow.
Discipline and parallels. The principal discipline is desire (φυσιολογία, non-attachment); the secondary is assent (dispelling the false valuation of "important / long-lasting"). Parallels: Med. 4.43 (04-43, the river of becoming), 2.17, 6.15 (in the stream nothing is stable), 05-13 (the endless transformation of the parts of the self).