Rene Descartes

I am certain that I am a thinking thing, and that I have a body, and that I am distinct from my body.

The greatest good is to live with reason, and therefore, to live without passions.

I know that I exist, but I do not know what I am.

The mind is more easily known than the body.

It is proper to a philosopher to doubt everything, at least once.

I think, therefore I am a doubt.

The soul is not in the body as a pilot in his ship, but intimately joined and intermingled with it.

I am a thinking substance, that is, a mind, or soul, or intellect, or reason.

The existence of God is a necessary consequence of my idea of God.

I have always held that the two questions, God and the Soul, were the chief of those which ought to be demonstrated by the help of philosophy rather than of theology.

Our knowledge of the external world is derived from our senses, and our senses are often unreliable.

The nature of the mind is entirely distinct from that of the body.

I found it possible to reject all my former beliefs, and to admit nothing as true that I had not clearly conceived.

The existence of God is as certain as any geometrical demonstration.

The chief cause of human error is the confused nature of our perceptions.

The light of natural reason shows us that there is a God.

I am a thinking thing, that is to say a mind, or a soul, or an understanding, or a reason.

The greatest good for man is to live according to reason.

I resolved to seek no other knowledge than that which I might find within myself, or in the great book of the world.

The existence of God is clearly demonstrated by the very idea of God.