"It is hard for a city composed in this way to change, but everything that comes in being must decay. Not even a constitution such as this will last for ever. It, too, must face dissolution." (VIII 546 a).
How are these statements plausible if there are just philosopher kings to check and balance the mistakes made by the lower classes of the city or even the mistakes that another philosopher king himself makes. To this, Plato would argue that his perfect rulers must eventually have a time when their sense perception is off and they miscalculate the timing of marriages and births in the city. This, then, will beget unworthy children that will grow to be unworthy citizens or rulers. In turn, these unworthy rulers will eventually create an even more hideous class of rulers, mainly tyrants. This is how Plato believes the fours lower stages of constitution will descend from the original aristocratic kallipolis. (VIII 546 a-c).
But how is Plato's argument about the decay of constitutions plausible? Do not the philosopher kings have the highest knowledge and do not they have the understanding of what the Form of Good is? Plato himself states that philosopher kings do have this knowledge and understanding. He says that a philosopher king is " by nature a friend and relative of truth, justice, courage, and moderation." (VI 487 e) It is understood, from the above paragraph, that the philosopher kings go through a period of faulty sense perception, but do all the philosopher kings go through this period at the same time? These philosopher kings most likely make individual miscalculations concerning marriages and births at individual times. If this were true, how can philosopher kings not notice the huge miscalculations and faulty sense perceptions revealed by their fellow philosopher kings? As they are described in book VI, it seems that philosopher kings have the knowledge and understanding to correct these mistakes and prevent the destruction of their good and just kallipolis.
