"If you would be a real seeker after truth, you must at least
once in your life doubt, as far as possible, all things."
"Of all things, good sense is the most fairly distributed:
everyone thinks he is so well supplied with it that even those
who are the hardest to satisfy in every other respect never
desire more of it than they already have."
"...long chains of perfectly simple and easy reasonings by
means of which geometers are accustomed to carry out their
most difficult demonstrations had led me to fancy that
everything that can fall under human knowledge forms a similar
sequence; and that so long as we avoid accepting as true what
is not so, and always preserve the right order of deduction of
one thing from another, there can be nothing too remote to be
reached in the end, or to well hidden to be discovered."
- René Descartes (1596-1650), Discours de la Methode (1637)