"Silence is a source of great strength."

"We don't see things as they are, we see them as we are."

"The only true wisdom is in knowing you know nothing."

"He who has a why to live can bear almost any how."

"Science is organized knowledge. Wisdom is organized life."

"Common sense is not so common."

"To know what you know and what you do not know, that is true knowledge."

"The only thing I know is that I know nothing."