Polity is the best form of government.

This statement is the best example of Aristotle's principle of golden mean. Aristotle believes that moderation is the best way of life. Polity is the best practicable form of government for following reasons:

1. Polity is a golden mean between two extremes- Oligarchy and democracy. Polity avoids extreme features of the 2 systems, Polity in the rule middle class. It is the rule of neither few nor many poor. Thus, it does not have problem of vices of two systems. 
2. Rule of the middle class is better because rich people do not have the habit of obedience to law whereas poor people lack the ability to rule. 
3. Both rich and poor have natural hatred against each other and both trust the middle class more than each other. 
4. Both rich and poor are naturally inclined to commit crime.

Thus, the rule of these classes that is rich and poor is not conducive for political stability and health of the society.

Middle class have the habit of obedience to law. Middle class possesses property so they have characteristics of responsibility. It is good because there are no glaring inequalities. So that is why the state should promote the middle class. Thus, Aristotle justified polity on the principle of golden mean.