Illusory joy is often worth more than genuine sorrow.

Intuition is the undoubting conception of a pure and attentive mind, which arises from the light of reason alone, and is more certain than deduction.

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

Each problem that I solved became a rule, which served afterwards to solve other problems.

It is best not to go on for great quest for truth , it will only make you miserable

I suppose therefore that all things I see are illusions; I believe that nothing has ever existed of everything my lying memory tells me. I think I have no senses. I believe that body, shape, extension, motion, location are functions. What is there then that can be taken as true? Perhaps only this one thing, that nothing at all is certain.

Although my knowledge grows more and more, nevertheless I do not for that reason believe that it can ever be actually infinite, since it can never reach a point so high that it will be unable to attain any greater increase.