Descartes: A Biography

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The Quarrel and Final Rift with Regius 

blameless life before this incident, and that provoked Descartes to inquire

into the causes of his uncharacteristic behaviour, since (he wrote to Huy-

gens), ‘as you know, I usually philosophize about everything that I notice,

(v.). This provided an opportunity to speculate about the affects of

the passions on otherwise blameless people, especially the commendable

passion to protect one’s own family, and to indicate the benefits of mod-

erating justice with clemency. He concludes: ‘If you do anything to allow

this poor man to return to his children, I can say that you will perform a

good action and that will be another reason for my being in debt to you’

(v.).

Descartes did not realize that theStadtholderwas very sick and that

he could hardly have been interested in the sentence passed on a peasant

from Egmond-Binnen.Huygens acknowledged Descartes’ intervention

in February, and that provided an added incentive for the French

philosopher to write a second time on behalf of the Jacobs family.The

details of the subsequent process are unclear, but the court of appeal issued

a more lenient judgment in January.

In the meantime, Descartes was contending with the harsh weather

conditions and the slow pace of his work. There were many obstacles to

completing the two sections that had been omitted from thePrinciples.

Although the word ‘exp ́erience’inFrench was used for both experiments

and observations, there was a big difference between observations that

could be done without any preparatory work and experimental tests that

required both equipment and skilled assistants. Descartes explained the

distinction to Chanut, by comparing his unplanned observation (in Febru-

ary)ofhexagonal snowflakes that simply fell from the sky, and the

sophisticated experimental observations that were now required to com-

plete his physics. ‘If all the experiences that I need for the rest of my

physics could fall from the clouds in that way, and if I needed only my

eyes to know them, I would hope to finish it [my physics] shortly. But

since one also needs hands to do them and since I do not have any hands

that are appropriate to the task, I am losing completely the desire to do

any further work on it.’

These frustratingly incomplete projects were interrupted by a request

from Charles Cavendish about pendulums with asymmetrical bobs.

Mersenne had also sent him a similar query, and the two invitations

provoked Descartes to return to the dispute he had had with Roberval

nine years earlier, following publication of theGeometry.One of the