Plato tested the king by stressing the radical difficulty and lifestyle transformation that true philosophy involves:
Those who are not really philosophers but have only a coating of opinions, like men whose bodies are tanned by the sun, when they see how much learning is required, and how great the labour, and how orderly their daily lives must be to suit the subject they are pursuing, conclude that the task is too difficult; and rightly so, for they are not equipped for this pursuit.
Plato describes this pursuit in detail:
Only when … names, definitions and visual and other perceptions have been rubbed against one another and tested, pupil and teacher asking and answering questions in good will and without envy, only then, when reason and knowledge are at the very extremity of human effort, can they illuminate the nature of any object.
As Plato wrote, philosophy ‘is not something that can be put into words like other sciences’. Instead, ‘after long-continued exchange between teacher and pupil, in joint pursuit of the subject, suddenly like light flashing forth when a fire is kindled, it is born in the soul and straight away nourishes itself.’ Rather than the competitive striving and isolation that define so much contemporary academic life, genuine philosophical practice requires friendships and collaboration devoted to advancing the flourishing of an entire community.
In The Birth of Tragedy (1872), Friedrich Nietzsche declared: ‘Knowledge kills action; action requires the veils of illusion.’ We still live under the dismal shadow of this belief. Our age of radical individualism and specialisation sanctions the split of knowledge and power, with academics pursuing one as politicians exercise the other. Plato’s Seventh Letter provides a different vision by recalling the intimate and necessary connection between philosophy and politics, community and justice, friendship and knowledge. Above all, it teaches us that action requires knowledge, and knowledge requires action. Knowledge is neither ‘illusion’, nor merely an instrument for the pursuit of power. It is a collective practice best cultivated in communities of philosophical friendship. An age of democracy doesn’t automatically need to abandon Plato’s ideal of the philosopher-king; we need only to expand it until friendship and education bind together as many people as possible into philosopher-citizens, ruling together in ‘good will’ and ‘without envy’.
https://aeon.co/essays/when-philosopher-met-king-on-platos-italian-voyages
Know Thyself 