The §kpÊrvsiw, or world's conflagration, followed by the restoration of an identical world seems to go against the rationality of the Stoic god. The aim of this paper is to show that Cleanthes, the second head of the School, can avoid this paradox. According to Cleanthes, the conflagration is an inevitable side-effect of the necessary means used by god to sustain the world. Given that this side-effect is contrary to god's sustaining activity, but unavoidable, god's rationality requires the restoration of an identical world once the conflagration subsides. The paper also deals with the relation between Cleanthes and other early Stoics on the topic of conflagration. In particular, Cleanthes' position seems to differ from Chrysippus'. For in contrast with the Cleanthean god, who causes the conflagration as a sideeffect only, the Chrysippean god, according to an influential interpretation put forward by Jaap Mansfeld, causes the conflagration as his ultimate cosmological goal.In orthodox Stoic theory, the present world (kÒsmow) will be destroyed by god through a mighty fire or 'conflagration' ( §kpÊrvsiw). Once the conflagration subsides, a restoration occurs, known as the épokatãstasiw. In it, god builds a new world, exactly identical to the present one. But if so, why does the Stoic god destroy the world in the first place? In this paper, I explore one possible answer to this question -that of Cleanthes, the second Head of the Stoic school (331-232 BCE).The idea of a conflagration followed by a restoration poses several philosophical problems. But the one just mentioned affects the rationality and goodness of god. The problem had already been perceived by Aristotle while attacking the notion that the world is perishable (De Philosophia fr. 19c Ross = fr. 21 Rose 3 ).If [the new world] is like [the old], its artificer will have laboured in vain (efi dɘmoiow, mataiopÒnow ı texn¤thw), differing in nothing from silly children, who often when playing on the beach make great piles of sand and then undermine them with their hands and pull them down again. (Barnes/Lawrence trans.)