Descartes: A Biography

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The ScientificEssaysand theDiscourse on Method 

Since this put a temporary block on discussing the fundamental principles

of physics or its underlying theory, Descartes turned his attention to spe-

cific phenomena, such as light, and developed some of the ideas on which

he had been working for the better part of five years. He argued against

Beeckman in Augustthat light is transmitted ‘in an instant’ from

its source to our eyes, and provided plausible arguments from eclipses

that there is no perceptible delay between seeing light leaving the sun and

seeing an eclipse of the moon. He rejected the alternative view, that light

travels so slowly that we can notice a time lapse between waving a torch

and seeing its reflection in a distant mirror, and concluded his statement

with a dismissive greeting: ‘If what I have written does not convince you,

Imust accept that nothing could do so. Goodbye’ (i.).

Research on optics continued. Jean-Baptiste Morin had sent Descartes a

presentation copy of his book on longitudes that had just been published in

Paris.As usual, Descartes wrote an effusive note of thanks, but without

taking time to read the book. However, he sympathized with Morin’s

complaint that basic research was not rewarded financially. He offered a

favourable comparison between his own commitment to research and that

of Morin, and regretted that neither of them was likely to benefit financially

from their efforts. ‘A craftsman who makes a good pair of glasses would earn

muchmore money from them than I would from all the reflections of my

Dioptricsif I were to sell them’ (i.). Twelve years later, Descartes was

still concerned about the possible commercialization of his dioptrical work.

InHuygens had sent him a copy of a book published in Paris, which

proposed a method for making spectacles.He wrote to both Mersenne

and Huygens about this report, on the same day. To Mersenne he wrote:

I recently saw a book...of a certain Jacques Bourgeois, a mirror and lens maker to

the king, who has his shop in Paris...from which I gather that this Mr. Bourgeois

has made ordinary spectacles which are worn on the nose, concave on one side and

convex on the other, in line with what I wrote at the beginning of the seventh and

ninth discourses of myDioptrics.Iindicated there that the shape of the lenses need

not be exact because we do not know exactly the shape of the eye, and besides it

is not inflexible. I would be very interested to find out if these spectacles are more

successful than what is normally available, if you have an opportunity to find out about

them.

With a shrewd insight into marketing strategies and, perhaps, his custom-

ary underestimation of others’ work, he told Huygens that the book was

merely the ‘rigmarole of a charlatan’, because ‘if the spectacles worked as