A State would be happy where philosophers were kings, or kings philosophers.
If you ask: What is the good of education? The answer is easy: Education makes good men and good men act nobly.
Reality is created by the mind, we can change our reality by changing our mind.
...that not life, but a good life, is to be chiefly valued.
And the quality of good judgement is clearly a form of knowledge and skill, as it is because of knowledge and not because of ignorance that we judge well.
Mathematics is like draughts in being suitable for the young, not too difficult, amusing, and without peril to the state.