" According to Plato, internal strife, class war, fomented by self-interest and especially material or economic self-interest, is the main force of ‘social dynamics’. The Marxian formula ‘The history of all hitherto existing societies is a history of class struggle’ fits Plato’s historicism nearly as well as that of Marx. The four most conspicuous periods or ‘landmarks in the history of political degeneration’, and, at the same time, ‘the most important … varieties of existing states’, are described by Plato in the following order. First after the perfect state comes ‘timarchy’ or ‘timocracy’, the rule of the noble who seek honour and fame; secondly, oligarchy, the rule of the rich families; ‘next in order, democracy is born’, the rule of liberty which means lawlessness; and last comes ‘tyranny … the fourth and final sickness of the city’.
As can be seen from the last remark, Plato looks upon history, which to him is a history of social decay, as if it were the history of an illness: the patient is society; and, as we shall see later, the statesman ought to be a physician (and vice versa)—a healer, a saviour.
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We see that Plato aimed at setting out a system of historical periods, governed by a law of evolution; in other words, he aimed at a historicist theory of society. This attempt was revived by Rousseau, and was made fashionable by Comte and Mill, and by Hegel and Marx; but considering the historical evidence then available, Plato’s system of historical periods was just as good as that of any of these modern historicists. (The main difference lies in the evaluation of the course taken by history. While the aristocrat Plato condemned the development he described, these modern authors applauded it, believing as they did in a law of historical progress.)
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It is important to note that Plato explicitly identified this best and oldest among the existing states with the Dorian constitution of Sparta and Crete, and that these two tribal aristocracies did in fact represent the oldest existing forms of political life within Greece. Most of Plato’s excellent description of their institutions is given in certain parts of his description of the best or perfect state, to which timocracy is so similar. (Through his doctrine of the similarity between Sparta and the perfect state, Plato became one of the most successful propagators of what I should like to call ‘the Great Myth of Sparta’—the perennial and influential myth of the supremacy of the Spartan constitution and way of life.) "

― Karl Popper , The Open Society and Its Enemies - Volume One: The Spell of Plato