Rene Descartes

I think, therefore I am.

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

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

Doubt is the origin of wisdom.

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

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

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

I hope that posterity will judge me kindly, not only as to the things which I have explained, but also as to those which I have intentionally omitted so as to leave to others the pleasure of discovery.

The power of judging well and of distinguishing the true from the false, which is properly what is called good sense or reason, is by nature equal in all men.

I desire to live in peace and to continue the life I have begun, adopting as my motto 'to live well, one must live concealed'.

To be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it.

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.

The greatest good for each of us is to live freely and happily.

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

For it is not enough to have a good mind, but rather it is necessary to apply it well.

I have been nourished by books, and I have found in them a great deal of good as well as a great deal of evil.

The first precept was never to accept anything for true which I did not clearly know to be such.

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

The will is by its nature so free that it can never be constrained.

He who has a firm and stable mind will find that in all conditions of life he can be master of himself.