I can doubt everything, except one thing, and that is the very fact that I doubt. Simply put - I think, therefore I am
Rene DescartesThe nature of matter, or body considered in general, consists not in its being something which is hard or heavy or coloured, or which affects the senses in any way, but simply in its being something which is extended in length, breadth and depth.
Rene DescartesIf ... it is not in my power to arrive at the knowledge of any truth, I may at least do what is in my power, namely, suspend judgement.
Rene Descartes