A. A. Long's Hellenistic Philosophy sets out how Stoic physics, developed by Zeno of Citium and elaborated in far greater technical detail by Chrysippus, held that the cosmos is a single living, rational body that periodically undergoes ekpyrosis, a total conflagration in which everything, including the other three classical elements, reverts to pure fire, the most active and divine of the elements in Stoic physics. Rather than an ending, the Stoics understood this conflagration as a return to the cosmos's purest state, the fiery divine reason, or Logos, that the Stoics identified with Zeus and held to be the active principle organizing all matter throughout every phase of the cycle, destructive as much as constructive.
From this state of pure fire, the Stoics held that a new cosmos is born, unfolding again through the four elements and the whole structured universe of stars, earth and living things, in a process called palingenesis, or rebirth, beginning the cycle anew. Long stresses that this was presented as sober physical doctrine following from Stoic premises about the nature of fire and divine reason, not as a speculative myth borrowed from outside the school, distinguishing it from the mythic world-age schemes of Hesiod or the Hindu yugas even though the overall shape, cosmic destruction followed by renewal, is broadly similar.