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

Even the mind depends so much on temperament and the disposition of one's bodily organs that, if it is possible to find a way to make people generally more wise and more skilful than they have been in the past, I believe that we should look for it in medicine. It is true that medicine as it is currently practiced contains little of much use.

I desire to live in peace and to continue the life I have begun under the motto 'to live well you must live unseen

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

Omnia apud me mathematica fiunt.

Here I beg you to observe in passing that the scruples that prevented ancient writers from using arithmetical terms in geometry, and which can only be a consequence of their inability to perceive clearly the relation between these two subjects, introduced much obscurity and confusion into their explanations.

When I consider this carefully, I find not a single property which with certainty separates the waking state from the dream. How can you be certain that your whole life is not a dream?