Descartes: A Biography

c CUNYB/Clarke     December, :

 Descartes: A Biography

Palais Royal. He wrote to him in June or July, in his usual style of answer-

ing detailed questions about physics, although on this occasion the queries

had been borrowed by Mersenne from some unidentified book that was

critical of Descartes’ optics.However, Mersenne fell ill onJuly and

never recovered. He suffered from an abscess that was initially diagnosed

as a false pleurisy, and his condition deteriorated during the following

month. He died onSeptember,atthe age of sixty, surrounded by

his confreres at the friary of Saint Francis of Paula, in central Paris, where

he had lived for most of his religious life. Although Mersenne was still alive

when Descartes left Paris, his health was evidently so precarious that, when

Descartes arrived in Amsterdam on his return journey, he wrote to Picot

to inquire about him.By then, unfortunately, the Minim friar had died.

Descartes had little opportunity to reflect on Mersenne’s contribution

to his work and on the often-strained relationship between them. However,

within a few months he realized that he no longer had someone in Paris

to whom he could direct his queries and from whom he could get reliable

information. Thus, when he wondered in Junewhether Pascal had

ever done the experiment on the Puy-de-Dome, he tried to find in Pierreˆ

Carcavi a plausible substitute for his erstwhile informer. In doing so, he had

occasion to reflect on the services over many years provided by Mersenne.

I had the benefit, when the good Father Mersenne was alive, that although I never

asked him about anything, I never failed to be informed in detail about everything that

was exchanged among the learned. Thus, although he sometimes had questions for me,

he repaid me very liberally with his replies by informing me about all the experiments

which he or others had performed, about all the unusual inventions which had been

found or sought, about all the new books that people thought were worthwhile, and

finally about all the controversies which occurred among the learned.

There was a real sense in which Mersenne was irreplaceable to Descartes.

No one else enjoyed the same stability (having lived in a friary in the centre

of Paris for thirty years), had contact with so many learned people both

in France and in other European countries, or had the time and energy

to write letters daily almost like a one-person clearing house for the dis-

semination of ideas. There were occasions when he caused controversies

that might have been avoided, and, in the opinion of some correspon-

dents, the depth of his intelligence did not always match the scope of

his interests.Once he had died, however, his personal failings seemed

relatively insignificant in comparison to the service he had provided as a