Rene Descartes

Doubt is the origin of wisdom.

Perfect numbers like perfect men are very rare.

I think, therefore I am.

If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.

It is not enough to have a good mind. The main thing is to use it well.

One cannot conceive anything so strange and so implausible that it has not already been said by one philosopher or another.

A state is better governed which has few laws, and those laws strictly observed.