He is unworthy of the name of man who is ignorant of the fact that the diagonal of a square is incommensurable with its side.

...in every man there is an eye of the soul, which...is more precious far than ten thousand bodily eyes, for by it alone is truth seen.

I prefer nothing, unless it is true.

The disposition of noble dogs is to be gentle with people they know and the opposite with those they don't know...How, then, can the dog be anything other than a lover of learning since it defines what's its own and what's alien.

Education and admonition commence in the first years of childhood, and last to the very end of life.

By education I mean that training in excellence from youth upward which makes a man passionately desire to be a perfect citizen, and teaches him to rule, and to obey, with justice. This is the only education which deserves the name.

The tyranny imposed on the soul by anger, or fear, or lust, or pain, or envy, or desire, I generally call 'injustice.'