"I shall proceed by setting aside all that in which I can suppose there to be the slightest doubt, just as if I had discovered that it was wholly false."

"The whole of philosophy is like a tree, whose roots are metaphysics, whose trunk is physics, and whose branches are all the other sciences."

"The greatest minds are capable of the greatest vices as well as of the greatest virtues."

"Our knowledge of the external world is derived from our senses, and our senses are often unreliable."

"The will, as far as it is considered formally in itself, is one of the chief perfections of man."