Every form of government tends to perish by excess of its basic principle. Aristocracy ruins itself by limiting too narrowly the circle within which power is confined; oligarchy ruins itself by the incautious scramble for immediate wealth. In either case the end result is revolution. When revolution comes it may seem to arise from little causes and petty whims; but though it may spring from slight occasions it is the precipitate result of grave and accumulated wrongs; when a body is weakened by neglected ills, the merest exposure may bring serious disease…
But even democracy ruins itself by excess -– of democracy. Its basic principle is the equal right of all to hold office and determine public policy. This is at first glance a delightful arrangement: it becomes disastrous because the people are not properly equipped by education to select the best rulers and wisest courses. “As to the people they have no understanding, and only repeat what their rulers are pleased to tell them” (Protagoras, 317); to get a doctrine accepted or rejected it is necessary only to have it praised or ridiculed in a popular play…
Plato complains that whereas in simpler matters –- like shoe-making -– we think that only a specially-trained person will serve our purpose, in politics we presume that every one who knows how to get votes knows how to administer a city or a state… To devise a method of barring incompetence and knavery from public office, and of selecting and preparing the best to rule for the common good -– that is the problem of political philosophy.
From Ch. 1 “Plato”, pt. V of The Story of Philosophy (Durant, Will)