When it is not in our power to determine what is true, we ought to follow what is most probable.
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.
If I find some reason for doubt in each of my beliefs, that will be enough to reject all of them.
I will follow this strategy until I discover something that is certain or, at least, until I discover that it is certain only that nothing is certain.
I was thus led to infer that the ground of our opinions is far more custom and example than any certain knowledge.
I took especially great pleasure in mathematics because of the certainty and the evidence of its arguments.
I think, therefore I am.
I am indeed amazed when I consider how weak my mind is and how prone to error.
I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake.
He who lives well lives well hidden.
He who hid well, lived well.