By three methods we may learn wisdom: First, by reflection, which is noblest; Second, by imitation, which is easiest; and third by experience, which is the bitterest.

Confucius

There is more intelligence in your body than in your best wisdom.

Nietzsche

I shall never cease from the practice and teaching of philosophy, exhorting anyone whom I meet after my manner, and convincing him, saying: O my friend, why do you who are a citizen of the great and mighty and wise city of Athens, care so much about laying up the greatest amount of money and honor and reputation, and so little about wisdom and truth and the greatest improvement of the soul, which you never regard or heed at all? Are you not ashamed of this? And if the person with whom I am arguing says: Yes, but I do care: I do not depart or let him go at once; I interrogate and examine and cross-examine him, and if I think that he has no virtue, but only says that he has, I reproach him with overvaluing the greater, and undervaluing the less.

Socrates

Discovery consists of seeing what everybody has seen and thinking what nobody has thought.

Albert Szent-Gyorgyi

Uncertainty is an uncomfortable position, but certainty is an absurd position.

Voltaire