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A: Leiden, Zuid-Holland, Netherlands

René Descartes Writes, "Je pense, donc je suis."

Title page of the first edition of Descartes, Discours de la methode
Title page of the first edition of Descartes, Discours de la methode (1637).

In 1637 French philosopher, mathematician, and scientist René Descartes issued his Discours de la méthode pour bien conduire sa raison, & chercher la verité‚ dans les sciences. As Descartes spent much of his life in the Dutch Republic, he had the work published in Leiden.

Descartes's Discours presented an outline of Cartesian scientific method, summed up in the famous Four Rules presented in Book 2, together with scientific treatises intended to illustrate the method's range. The four rules may be stated as :

 1. "The first was never to accept anything for true which I did not clearly know to be such; that is to say, carefully to avoid precipitancy and prejudice, and to comprise nothing more in my judgment than what was presented to my mind so clearly and distinctly as to exclude all ground of doubt.

2. "The second, to divide each of the difficulties under examination into as many parts as possible, and as might be necessary for its adequate solution.

3. "The third, to conduct my thoughts in such order that, by commencing with objects the simplest and easiest to know, I might ascend by little and little, and, as it were, step by step, to the knowledge of the more complex; assigning in thought a certain order even to those objects which in their own nature do not stand in a relation of antecedence and sequence.

4.  "And the last, in every case to make enumerations so complete, and reviews so general, that I might be assured that nothing was omitted.

"The enumerations have in time developed into many forms. He suggested drawing boxes on a paper, and connecting them. This idea has led to a multitude of graphic thinking aids that we use today" (Wikipedia article on Discourse on the Method, accessed 03-03-2009).

The work includes three scientific treatises: Dioptrique, containing Descartes's derivation of the law of refraction; Météores; and Géométrie. The work included his invention of the Cartesian coordinate system and the foundation of analytic geometry, the bridge between algebra and geometry, crucial to the invention of calculus and analysis. Though Descartes' most  famous statement is best known by its Latin translation, it was first published in the Discours as "Je pense, donc je suis," and later translated into Latin in his Principia philosophiae as "Cogito, ergo sum."

Carter & Muir, Printing and the Mind of Man (1967) no. 129. Hook & Norman, The Haskell F. Norman Library of Science and Medicine (1991) no. 621.

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