The Republic Book VIII begins when Plato has already arrived to his conclusion for the best form of government. He believes, as he talks to Glaucon about it, that the best King is one who is the best of philosophers and the best at war. Plato was more of a political philosopher and all his other theories were in some ways helping his theories on politics. Hence, we can assume that they were derived to support his political theories. For instance, his theory of Ideal Forms and his theory about psyche or soul also establish his political theory. He also believes that “political science” is the most important form of education.
Plato tells us that everything decays and therefore, forms of government also decay. The best form of government deteriorates into a less perfect form and then an even lesser appreciated form. Likewise, the form of government diminishes in character and integrity to become the worst of all forms.
Although, Plato uses the number four for his stages of governance or forms of government in the Republic, he actually talks about five particular forms. He starts with the best and shows us how one stage transforms into another stage of governance because of deterioration.
The first stage of political governance is the best form of government according to Plato. It is called aristocracy or government of the best. The ruler has to be the best of philosophers and the best at war as mentioned earlier. Excellence and education is a priority and equality is observed under the rule of an aristocrat.
An aristocracy changes mildly into a timocracy or government of honor. This form of government is one in which the ruler is more involved in warfare, hence, a government of honor comes to being. The ruler is honored by public and this makes it similar to an aristocracy but the state is involved more into warfare. Plato, also, explains how timocracy comes to being in the first place. According to Plato, there are particular periods in which people should have babies and when babies are born otherwise it leads to deterioration and inequality. Metals are mixed when they shouldn’t; hence, bronze and iron combine to fight for money, while silver and gold come together and fight to bring back aristocracy. This brings chaos and inequality which causes a state involved in warfare.
Similarly, timocracy degrades into an oligarchy. Oligarchy is a government of few and the rich are the few that rule the majority of the poor. Oligarchy just naturally evolves from timocracy because a nation indulged in war will accumulate a lot of wealth and it will lose its respect for excellence. The few rich people will begin to rule and suppress the poor. The rich will be scared of arming the poor majority, fearing they will turn on them and the state will be a weak one. Extreme poverty will bring crime rate and illiteracy to their peaks.
The poor majority will soon come together to form an even worse form of government, democracy. This is the form of government in which everyone wants to be rich, Plato believed. Democracy takes birth when rich have made the poor loathe them and love of revolution begins to spring amongst poor. Therefore some revolutionists rise and either kill or exile the rich rulers, forming a new, just government with freedom as their priority. In a rule like this one there is no compulsion for anything. You can choose to not join the army even if you are competent. The insatiable desire of freedom forms a nation where teachers fear students and children fight parents. Hence, people start disregarding all laws and nobody wants to be ruled. Although, someone obviously does rule and they are slightly richer than all the other population. The common people start taking their rulers as oligarchs. This is when someone stands up as the defender of democracy.
This is where another form of government and the worst of all, comes to existence. The defender of democracy makes all sorts of promises and pretends very kind in the beginning. He overthrows the rulers and when he has defended democracy and is no longer required, he keeps bringing fake problems to make the people feel that they need him. When the people discover he is not needed and they stand for that, the true face unleashes and we find that the defender of the democracy is a tyrant. This is how the fifth, most repulsive stage of governance, tyranny, comes to being.
Now one way to put down Plato’s five stages of governance were to simply name and describe them. But, I believe, this is not how Plato wants us to know them. He wants us to know them in the form he writes, as to show which form deteriorates to which and which one is the best. Aristocracy is the best and it keeps deteriorating from timocracy to oligarchy to democracy and then to the worst, tyranny.
 Translated by Allan Bloom, The Republic of Plato, Second Edition, (United States: 1991), p. 221.
 Translated by Lenora Cohen, Alexandre Koyre’s Discovering Plato, (New York: Columbia University press, 1945), p. 53.
 Translated by Benjamin Jowett, The Republic, Third Edition, (Oxford: Clarendon Press, 1936), p.205
 Translated by Allan Bloom, The Republic of Plato, Second Edition, (United States: 1991), p. 222
 Translated by Allan Bloom, The Republic of Plato, Second Edition, (United States: 1991), p. 223.
 Translated by Benjamin Jowett, The Republic, Third Edition, (Oxford: Clarendon Press, 1936), p. 206
 Translated by Allan Bloom, The Republic of Plato, Second Edition, (United States: 1991), p. 241.
 Translated by Allan Bloom, The Republic of Plato, Second Edition, (United States: 1991), p. 243.