The Stoic cosmos is cyclical in returning. Every cosmic cycle ends in an ἐκπύρωσις (a universal conflagration: all things return to the primary creative fire, πῦρ τεχνικόν); there follows a διακόσμησις — a new ordering of the world from the same fire; and the whole process repeats. The crucial point is that the repetition occurs in the very same forms (ὁμοειδῶς, ταὐτά): not "similar" events, but the same Socrates will drink the same hemlock, the same Alexander will conquer the same Asia. This is numerical return, not an "echo" or a "reminiscence."

The logic of the Stoic argument:

1. The cosmos is governed by a single TERMLogos / TERMfate;
2. That Logos is absolutely complete and has no discernible "alternatives": given the matter and the Logos, the outcome is fixed;
3. After the TERMcosmic cycles matter returns to its initial state, while the Logos remains unchanged;
4. ⇒ The next cycle reproduces the same course of events, numerically identical.

In this the Stoic position differs radically from the Platonic (where the Ideas exist outside the cosmos and the cosmos imitates them, which leaves room for inexact realisation) and from the Epicurean (where chance clinamina introduce into the cosmos an irreducible variability). For the Stoic the repetition is absolute, because causation is absolute.

SVF I 109 (Zeno on the conflagration); I 497–512 (Cleanthes); II 596–632 (Chrysippus — the main corpus on the cosmic cycles); II 599 (παλιγγενεσία, "rebirth"); the classical doxographies: DL VII 142; Plut. De Stoic. rep. 1052b–c; De comm. not. 1067a (Plutarch criticises the doctrine as inconsistent with the godlikeness of the sage, who, supposedly, would have to give the same assents in every cycle); Origen C. Cels. IV 67; V 20 (the Christian polemic); Cic. De nat. deor. II 118 (the conflagration); LS 46 ("Cosmogony, cosmology, and immortality"), 52 ("Causation and fate"). In Marcus the theme of cosmic periodicity is a leitmotif: Med. 2.14; 5.13; 6.4 (the world in eternal cycle); 6.15; 6.37 ("the one who has seen the present has seen all"); 7.19; 9.28; 10.7; 11.1; 12.26.

In 02-14 the doctrine of return works as the great leveller of life-durations: "all things from eternity are of one kind and recur, and therefore it makes no difference whether a person observes the same things for a hundred years, two hundred, or infinite time" (πάντα ἐξ ἀιδίου ὁμοειδῆ καὶ ἀνακυκλούμενα καὶ οὐδὲν διαφέρει...). This is an ethical argument drawn from physics: the duration of a life is an indifferent, because on the cosmic scale a long life and a short life observe the same things; neither receives "more that is unique." The long-liver does not see more — he sees the same things for longer.

The connection with the memory of death: eternal recurrence makes death not a finale but simply a moment in an infinite series. For the Stoic this is not consolation by way of personal immortality (the Socrates of cycle N+1 does not "remember" the life of cycle N — these are distinct subjectivities, even though they are numerically identical acts): the doctrine does its work not on individual hope but on cosmic levelling. Paradoxically: precisely because I myself do not return, my death is no exceptional catastrophe — the cosmos will produce me (and my contemporaries) again and again, without my participation.

The connection with Nietzsche: Nietzsche takes this Stoic idea directly (with Heraclitus as intermediary) and turns it into an existential thesis: "if this very moment were to recur eternally — could you will it?" In the Stoics no such question is posed: for them the repetition is a cosmological fact, not the object of acceptance or refusal. But the structural resemblance is large, and part of the Nietzschean force of the doctrine descends from its Stoic origin.

See also TERMmetabole — the cyclical transformation of the elements as the mechanism of return; TERMheimarmene — the deterministic Logos that secures the identity of the cycles.