=210.= In connexion with the doctrine of the conflagration the Stoics were called upon to take sides upon the favourite philosophic problem whether the universe is perishable, as Democritus and Epicurus hold, or imperishable, as the Peripatetics say[114]. In replying to this question, as in the theory as a whole, they relied on the authority of Heraclitus[115]. The word universe is used in two senses: there is an eternal universe (namely that already described as the universal substance made individual by the possession of quality[116]), which persists throughout an unending series of creations and conflagrations[117]. In another sense the universe, considered in relation to its present ordering, is perishable[118]. Just in the same way the word ‘city’ is used in two senses; and that which is a community of citizens may endure, even though the collection of temples and houses also called the ‘city’ is destroyed by fire[119]. [Sidenote: Dissentient Stoics.] =211.= The doctrine of the conflagration was not maintained by all Stoic teachers with equal conviction. Zeno treated it with fulness in his book ‘on the universe[120]’; and Cleanthes and Chrysippus both assert that the whole universe is destined to change into fire, returning to that from which, as from a seed, it has sprung[121]. In the transition period, owing to the positive influence of Plato and Aristotle, and the critical acumen of Carneades, many leading Stoics abandoned the theory[122]. Posidonius however, though a pupil of Panaetius (the most conspicuous of the doubters[123]), was quite orthodox on this subject; though he pays to his master the tribute of asserting that the universe is the most permanent being imaginable[124], and that its existence will continue through an immense and _almost_ unlimited period of time[125]. In the Roman period the conflagration is not only an accepted dogma, but one that makes a strong appeal to the feelings. For with the conflagration there comes to an end the struggle of the evil against the good; and the Deity may at last claim for himself a period of rest, during which he will contemplate with calmness the history of the universe that has passed away[126], and plan for himself a better one to follow[127]. [Sidenote: The reconstruction.]