Even the noise of traffic does not interrupt my reveries any more than would that of some rivulet." Having devoted himself for a long time past to the study of geometry and astronomy, he composed in Holland his Treatise on the World (_Traite du Monde_).

"I had intended to send you my _World_ for your New Year's gift," he wrote to the learned Minime, Father Mersenne, who was his best friend; "but I must tell you that, having had inquiries made, lately, at Leyden and at Amsterdam, whether Galileo's system of the world was to be obtained there, word was sent me that all the copies of it had been burned at Rome, and the author condemned to some fine, which astounded me so mightily that I almost resolved to burn all my papers, or at least not let them be seen by anybody.

I confess that if the notion of the earth's motion is false, all the foundations of my philosophy are too, since it is clearly demonstrated by them.

It is so connected with all parts of my treatise that I could not detach it without rendering the remainder wholly defective.

But as I would not, for anything in the world, that there should proceed from me a discourse in which there was to be found the least word which might be disapproved of by the church, so would I rather suppress it altogether than let it appear mutilated." Descartes' independence of thought did not tend to revolt, as he had proved: in publishing his _Discourse on Method_ he halted at the threshold of Christianism without laying his hand upon the sanctuary.
Making a clean sweep of all he had learned, and tearing himself free, by a supreme effort, from the whole tradition of humanity, he resolved "never to accept anything as true until he recognized it to be clearly so, and not to comprise amongst his opinions anything but what presented itself so clearly and distinctly to his mind that he could have no occasion to hold it in doubt." In this absolute isolation of his mind, without past and without future, Descartes, first of all assured of his own personal existence by that famous axiom, "Cogito, ergo sum" (I think, therefore I am), drew from it, as a necessary consequence, the fact of the separate existence of soul and of body; passing oft by a sort of internal revelation which he called innate ideas, he came to the pinnacle of his edifice, concluding for the existence of a God from the notion of the infinite impressed on the human soul.