I did not imitate the skeptics who doubt only for doubting's sake, and pretend to be always undecided; on the contrary, my whole intention was to arrive at a certainty, and to dig away the drift and the sand until I reached the rock or the clay beneath.

I was convinced that our beliefs are based much more on custom and example than on any certain knowledge.

It's the familiar love-hate syndrome of seduction: "I don't really care what it is I say, I care only that you like it."

In the matter of a difficult question it is more likely that the truth should have been discovered by the few than by the many.

The only secure knowledge is that I exist.

Reason is nothing without imagination.

These 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.