Book 2 · Section 38

(38) When therefore a want and terrible scarcity of virtue seizes upon cities, and when a great abundance of folly overwhelms everything, then God, like the stream of an overflowing torrent, being desirous to wash away all the power and impetuosity of wickedness, in order to purify our race, gives vigour and power to those men who by their natures are fitted to exercise dominion, (39) for without a stern soul wickedness cannot be got rid of. And just as cities keep executioners for the punishment of murderers, and traitors, and sacrilegious persons, not because they approve of the dispositions of the men, but because they have need of the serviceable part of their ministrations; in the same manner the Ruler of this mighty city, the world, appoints tyrants, like ordinary executioners, to be over those cities in which he sees that violence, and injustice, and impiety prevail, and all other kinds of evils in abundance, that he may by these means put an end to their existence. (40) And then he thinks it right to pursue the guilty, as men who have been serving these vices from the impulses of an impure and pitiless soul, with every punishment imaginable, as the ringleaders; for as the power of fire when it has consumed the fuel which was given to it, at last consumes itself also, so also do those who have received supreme power over nations, when they have exhausted the cities and rendered them destitute of inhabitants, at last perish themselves among them, suffering due punishment for all that they have done.