Descartes: A Biography

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 Descartes: A Biography

about mathematical problems, which were about the furthest thing from

his mind, that he hoped to turn Roberval’s critique to his own advantage.

If Roberval prevailed, his success might at least have the beneficial effect

of persuading everyone that Descartes had completely forgotten how to

do mathematics.

Although Descartes made no progress with Roberval, he completed a

first draft of what was eventually published as theTreatise on the Passions

of the Soul.Hehad visited The Hague onMarchand had left

forPrincess Elizabeth a first draft of this book.He exaggerated the

modesty of his efforts with the excuse that he had never studied the subject

previously.However, the underlying theory on which his account of

human emotions depended was the still-incompleteTreatise on Man. This

had been drafted as part of the more comprehensive project calledThe

World, which Descartes had withdrawn in.Heprobably made some

amendments to this draft as he did further work in anatomy during the

intervening years. Sometime in,heallowed copies of theTreatise on

Manto be made, probably by Van Surck and by Pollot.He had shown

a copy of this draft to Princess Elizabeth, sometime before October,

which provided an outline theory of how thoughts are associated with

brain states.He was thus able to borrow from that work to express one

of the fundamental insights of his account of mind-body interaction, the

novelty of which he was attempting to protect from any prior unauthorized

publication by Regius.

There is such a close liaison between our soul and our body that the thoughts that

have accompanied certain movements of our body from the beginning of our lives still

accompany them today. Therefore, if the same movements are triggered afresh in the

body by some external cause, they also stimulate the same thoughts in the soul and,

reciprocally, if we have the same thoughts, they produce the same bodily movements.

Finally, the machine of our body is constructed in such a way that a single thought

of joy, or love, or some other similar thought, is sufficient to send the animal spirits

through the nerves into all the muscles that are needed to cause the movements of

blood which, I claimed, accompany the passions....One can move thehand or the

foot almost at the instant that one thinks of moving them because the idea of this

movement, which is formed in the brain [cerveau], sends the spirits to the muscles that

are appropriate for this movement.

This is a long way from the speculations about ‘pure thought’ that dis-

tracted and misguided readers of theMeditations. Descartes relies on a