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

M. Desargues puts me under obligations on account of the pains that it has pleased him to have in me, in that he shows that he is sorry that I do not wish to study more in geometry, but I have resolved to quit only abstract geometry, that is to say, the consideration of questions which serve only to exercise the mind, and this, in order to study another kind of geometry, which has for its object the explanation of the phenomena of nature... You know that all my physics is nothing else than geometry.

我思う故に我あり

Several years have now passed since I fi rst realized how numerous were the false opinions that in my youth I had taken to be true, and thus how doubtful were all those that I had subsequently built upon them. And thus I realized that
once in my life I had to raze everything to the ground and begin again from the
original foundations, if I wanted to establish anything firm and lasting in the sciences.