In the Nomoi, Plato writes his mature reflections. With the aim of thinking to project of a new constitution that can be realized, especially in the first books considered authentic proems to the book, Plato presents the basis for a sort of philosophy of history, according to which, after millennia from each other, humanity purifies itself through great catastrophes, from which only a few men are able to save. A theory taken into consideration for a long time in the ancient world and which also finds reference in previous dialogues, in particular in the Timaeus. According to the Athenian philosopher, these cataclysms represent the starting point for the birth of human activities, and, therefore, of the institutions and techniques which, passing through various historical phases, determine the corruption, mostly of the soul. But in this development, how can this logical reasoning of philosophy of history be placed within the constitutional theories already thought by Plato?