Place in the book. A passage of physics: what I am made of, where I shall go — and why this is nothing to fear. The discipline of desire, rooted in physics: to understand the constitution of the cosmos is to accept one's place in it.

The two principles. "I consist of the causal (αἰτιῶδες) and the material (ὑλικόν)" — the Stoic two first principles (δύο ἀρχαί): the active, τὸ ποιοῦν (the Logos, god), and the passive, τὸ πάσχον (ὕλη, matter). Both are eternal: nothing perishes into non-being nor arises out of non-being (a law of conservation). Long renders αἰτιῶδες as "the formal" — the active, form-giving principle.

Endless change. Since both principles are indestructible, every part of me will by TERMchange (μεταβολή) become a part of the cosmos, and that another part, and so without end; and I too arose by such a change, and my parents before me, and so backward without end. The "I" is a transient node in a ceaseless transformation, not an island sprung from nothing. Cf. 04-14: the return of the part into the seminal reason of the Whole by transmutation.

Eternal recurrence. The closing proviso: "even if DOGMAthe cosmos is administered by finite periods" (κατὰ περιόδους πεπερασμένας) — the Stoic cyclical cosmos: the world periodically dissolves into the creative fire (ἐκπύρωσις) and is reborn identical (παλιγγενεσία). Marcus notes that his argument holds on either cosmology — whether time is infinite and linear, or a series of finite recurring cycles.

The consolation. Hence an implicit therapy of death: since I am composed of eternal principles and merely transform (I do not vanish), there is nothing dreadful in death — pure physics grounding acceptance (cf. death as the σύγκρισις/λύσις of the elements). This is the "discipline of desire" at its physical root.

Discipline and parallels. The principal discipline is desire (EXERCISEthe contemplation of nature that leads to acceptance). The term is TERMmetabole; the doctrines are DOGMAeternal recurrence and DOGMAthe unity of the cosmos. Parallel: Med. 4.14 (04-14).