René Descartes

1. “I think; therefore I am.”
   -René Descartes
2. “If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.”
   -René Descartes
3. “One cannot conceive anything so strange and so implausible that it has not already been said by one philosopher or another.”
   -René Descartes