Descartes: A Biography

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AFabulous World (–) 

lenses. With this in mind, he tried to persuade Ferrier, an experienced

lens grinder who was then in the service of the king’s brother in Paris, to

travel to Franeker and to work under his supervision. Descartes explained,

sensibly enough, that many technical problems arise in the course of grind-

ing lenses that cannot be anticipated in theory or adequately explained in

correspondence. However, if Ferrier were to work side by side with him,

they could resolve such problems more efficiently. The invitation natu-

rally extolled the benefits of a remote place that the reluctant French lens

grinder had presumably never even heard of:

If you were gallant enough to make the journey and come to spend some time with me in

the wilderness, you would have all the free time to train yourself, no one would distract

you, and you would be removed from anything that could disturb your peace....we

would live as brothers, because I guarantee to pay your expenses for as long as you

agree to stay with me, and to send you back to Paris as soon as you wish to return

there. (i.)

He would have to bring his own tools with him, Descartes tells Ferrier, but

he need not incur any travel costs beyond Calais. From Calais it is possible

to cross by sea to Dordrecht, and the trip from there to Franeker is as easy

as going to church in Paris. Once arrived in Dordrecht, he should go to see

Beeckman, who is rector of the local college, and he would supply him with

money for his journey and anything else he needed. Descartes does not

give Ferrier precise instructions about where to find him in Franeker, for

fear that he might share the information with others in Paris. Beeckman

is also designated as an intermediary for this purpose, to tell him how to

complete his journey, but Ferrier must then keep secret the exact address

of what is envisaged as a workshop for two French lens grinders. Almost

as an afterthought, Descartes asks Ferrier to bring a camp-bed with a

mattress, because the local beds are uncomfortable (i.).

This invitation failed to persuade the reluctant Ferrier, although it is

clear that Descartes was very keen to exploit his talents. He commends

his optical skills to another correspondent in September, claiming that

he knows ‘no one in the world who is as skilled as he is in his craft’

(i.). In fact, Ferrier was said to be so gifted in the mathematics of

manipulating light and air that ‘he can cause all the illusions that magi-

cians are said to cause with the assistance of demons’ (i.).Despite

the warmth of the invitation and the exaggerated compliments about his