The grounds of those persuasions which are to be found amongst men, so various, different, and wholly contradictory; and yet asserted somewhere or other with such assurance and confidence, that he that shall take a view of the opinions of mankind, observe their opposition, and at the same time consider the fondness and devotion wherewith they are embraced, the resolution and eagerness wherewith they are maintained, may perhaps have reason to suspect, that either there is no such thing as truth at all, or that mankind hath no sufficient means to attain a certain knowledge of it.
The Philosophical Works of Descartes, ed., tr. Elizabeth S. Haldane and GRT Ross (New York: Dover, 1955, orig; Meditations on First Philosophy, orig. 1647), p. 144
It is now some years since I detected how many are the false beliefs that I had from my earliest youth admitted as true, and how doubtful was everything I had since constructed on this basis, and from that time I was convinced that I must once for all seriously undertake to rid myself of all the opinions which I formerly accepted, and commence to build anew from the foundation…