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

Common sense is the most widely shared commodity in the world, for every man is convinced that he is well supplied with it.

Doubt is the origin of wisdom.

Conquer yourself rather than the world.

The only thing we have power over is our own mind.

Cogito, ergo sum.

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

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.

I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake.

To live without philosophizing is in truth the same as keeping the eyes closed without attempting to open them.

The preservation of health should be the first study of those who are wise.

Except our own thoughts, there is nothing absolutely in our power.

The first precept was never to accept a thing as true until I knew it as such without a single doubt.

Divide each difficulty into as many parts as is feasible and necessary to resolve it.

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

The greatest minds are capable of the greatest vices as well as of the greatest virtues.

I think, therefore I am.

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

For I found myself embarrassed with so many doubts and errors that it seemed to me that the effort to instruct myself had no effect other than the increasing discovery of my own ignorance.

He who hid well, lived well.