René Descartes

A man is but the product of his thoughts; what he thinks, he becomes.

From The Philosophical Writings of Descartes

Cogito, ergo sum.

From The Philosophical Writings of Descartes

To live without Hope is to Cease to live.

From The Philosophical Writings of Descartes

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

From The Philosophical Writings of Descartes

The passions can be regulated by reason.

From The Passions of the Soul

Fear is the passion that most commonly affects the mind.

From The Passions of the Soul

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.

From The Philosophical Writings of Descartes

The more perfect a thing is, the more of it is required.

From The Philosophical Writings of Descartes

Joy is a passion that arises from the knowledge of a present good.

From The Passions of the Soul

The mind is a thing that thinks.

From The Philosophical Writings of Descartes