Rene Descartes

The greatest minds, as they are capable of the highest excellencies, are open likewise to the greatest aberrations.
~ in Discourse On Method

No opinion, however absurd and incredible, can be imagined, which has not been maintained by some one of the philosophers.
~ in Discourse On Method

Except our own thoughts, there is nothing absolutely in our power.
~ in Discourse On Method

What is there, then, that can be esteemed true? Perhaps this only that there is absolutely nothing certain.
~ in Meditationes de prima philosophia

The reading of all good books is like conversation with the finest men of past centuries.