"To be able to live without fear, without anxiety, without sadness, and without any other passion which could disturb the tranquillity of the soul."

"I have always taken the greatest pleasure in seeking out and acquiring knowledge."

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

"The mind is a substance whose whole essence or nature is to think, and which needs no place, nor depends on any material thing, in order to exist."

"I think, therefore I am."