“I must go beyond the dark world of sense information to the clear brilliance of the sunlight of the outside world. Once done, it becomes my duty to go back to the cave in order to illuminate the minds of those imprisoned in the 'darkness' of sensory knowledge.”

“Here's something else I'd like your opinion about," I said. "If he went back underground and sat down again in the same spot, wouldn't the sudden transition from the sunlight mean that his eyes would be overwhelmed by darkness?" "Certainly," he replied. "Now, the process of adjustment would be quite long this time, and suppose that before his eyes had settled down and while he wasn't seeing well, he had once again to compete against those same old prisoners at identifying those shadows. Would he make a fool of himself? Wouldn't they say that he'd come back from his upward journey with his eyes ruined, and that it wasn't even worth trying to go up there? And would they -- if they could -- grab hold of anyone who tried to set them free and take them up there and kill him?”

“Whereas, our argument shows that the power and capacity of learning exists in the soul already; and that just as the eye was unable to turn from darkness to light without the whole body, so too the instrument of knowledge can only by the movement of the whole soul be turned from the world of becoming into that of being, and learn by degrees to endure the sight of being, and of the brightest and best of being, or in other words, of the good.”

“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.”

“To go to the world below, having a soul which is like a vessel full of injustice, is the last and worst of all the evils”

“The society we have described can never grow into a reality or see the light of day, and there will be no end to the troubles of states, or indeed, my dear Glaucon, of humanity itself, till philosophers become rulers in this world, or till those we now call kings and rulers really and truly become philosophers, and political power and philosophy thus come into the same hands.”

“A library of wisdom, is more precious than all wealth, and all things that are desirable cannot be compared to it. Whoever therefore claims to be zealous of truth, of happiness, of wisdom or knowledge, must become a lover of books.”