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 two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge.
• 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.
• 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.
• I hope that posterity will judge me kindly, not only as to the things which I have explained, but also to those which I have intentionally omitted so as to leave to others the pleasure of discovery.
• The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge.
• Perfect numbers like perfect men are very rare.
• Except our own thoughts, there is nothing absolutely in our power.
• When it is not in our power to follow what is true, we ought to follow what is most probable.