Human behavior flows from three main sources: desire, emotion, and knowledge.

I was stupid enough to think that we ought to speak the truth about each person eulogised, and to make this the foundation, and from these truths to choose the most beautiful things and arrange them in the most elegant way; and I was quite proud to think how well I should speak, because I believed that I knew the truth.

You ought not attempt to cure the eyes without the head, or the head without the body, so neither ought you attempt to cure the body without the soul.

Renouncing the honors at which the world aims, I desire only to know the truth... and to the maximum of power, I exhort all other men to do the same.

True opinions are a fine thing and do all sorts of good so long as they stay in their place; but they will not stay long. They run away from a man's mind, so they are not worth much until you tether them by working out the reason. Once they are tied down, they become knowledge, and are stable.

Let no-one ignorant of geometry enter. Said to have been inscribed above the door of Plato's Academy.

The human race will have no respite from evils until those who are really philosophers acquire political power or until, through some divine dispensation, those who rule and have political authority in the cities become real philosophers.