In the Republic, having discussed the class of producers and the class of guardians, Socrates goes on to discuss the third and last class of citizen in his ideal State, the class of rulers.

Rulers should be chosen from amongst the guardians after close observation and rigorous testing of their loyalty to the State.

Guardians who are chosen as rulers should receive further education; guardians who are not chosen as rulers should no longer be known as ‘guardians’ but as ‘auxiliaries,’ whose role it is to implement the will of the rulers.

Socrates says that all the citizens should be told a useful lie so as to promote allegiance to the State and enforce its three-tiered social order.

According to this myth of the metals, every citizen is born out of the earth of the State and every other citizen is his brother or sister. Yet God has framed them differently, mixing different metals into their soul: gold for the rulers, silver for the auxiliaries, and brass or iron for the husbandmen and craftsmen.

Children are usually made of the same metal as their parents, but if this is not the case the child must either descend or ascend in the social order. If ever a child made of brass or iron was to become a guardian, the State would be destroyed.

As guardians are made of divine gold and silver, they should have nothing to do with the earthly sorts which have been ‘the source of many unholy deeds’.

Guardians should not have any private property; they should live together in housing provided by the state, and receive from the citizens no more than their daily sustenance.

Guardians may be the happiest of men in spite, or because, of their deprivations, for the arts and crafts are equally liable to degenerate under the influence of wealth as they are under the influence of poverty: ‘the one is the parent of luxury and indolence, and the other of meanness and viciousness, and both of discontent’.

Neel Burton is author of The Gang of Three: Socrates, Plato, Aristotle.