SOCRATES: Perhaps we may be wrong; if so, you in your wisdom should convince us that we are mistaken in preferring justice to injustice. THRASYMACHUS: And how am I to convince you, he said, if you are not already convinced by what I have just said; what more can I do for you? Would you have me put the proof bodily into your souls?
PlatoWhen the mind's eye rests on objects illuminated by truth and reality, it understands and comprehends them, and functions intelligently; but when it turns to the twilight world of change and decay, it can only form opinions, its vision is confused and its beliefs shifting, and it seems to lack intelligence.
PlatoTrue 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.
Plato