"It is a mark of a truly great mind to be able to make a great discovery with few means."

"I consider that I possess no senses; I imagine that body, figure, extension, motion and place are but fictions of my mind."

"I concluded that I was a substance whose whole essence or nature consists only in thinking, and that, in order to exist, it needs no place and depends on no material thing."

"I should know better than to believe that everything I perceive through my senses is true."

"Divide each difficulty into as many parts as is feasible and necessary to resolve it."