"The difference between us is that I am a man of the world, and you are a man of books."

"I desire to live in peace and to continue the life I have begun, adopting as my motto 'to live well, one must live concealed'."

"I think, therefore I am — this is the first and most certain conclusion that anyone who philosophizes in order should arrive at."

"It is not enough to apply our mind to things, but we must also apply it to ourselves."

"I know that I exist, but I do not know what I am."