The analogy between the legislator and the craftsman on which Plato insists, breaks down because the legislator is dealing with men like himself, men who can to some extent conceive their own end in life and cannot be treated merely as means to the end of the legislator.

The sense of the value of "ruling and being ruled in turn" is derived from the experience that the ruler may use his power to subordinate the lives of the citizens of the state not to the common good but to his own private purposes.

In modern terms, it is a simple, rough-and-ready attempt to solve that constant problem of politics, how efficient government is to be combined with popular control.

This problem arises from the imperfection of human nature, apparent in rulers as well as in ruled, and if the principle which attempts to solve it be admitted as a principle of importance in the formation of the best constitution, then the starting-point of politics will be man's actual imperfection, not his ideal nature.

Instead, then, of beginning with a state which would express man's ideal nature, and adapting it as well as may be to man's actual shortcomings from that ideal, we must recognise that the state and all political machinery are as much the expression of man's weakness as of his ideal possibilities.