"The tendency to aggression is an innate, independent, instinctual disposition in man... it constitutes the most powerful obstacle to culture."

"No one who has tasted the forbidden fruit of knowledge can ever again be satisfied with the primitive bliss of ignorance."

"Obsessive cleanliness is not a sign of virtue. It is a symptom of an anal character."

"I consider myself to be a man of science, not a philosopher."

"Where id was, there ego shall be."