8 - Two natural philosophies  pp. 179-226

Two natural philosophies

By Roger French

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Descartes reads De motu cordis

For Harvey's doctrines to be rejected, or sufficiently accepted to form the basis of a new consensus, they had to be known. Some people read De motu cordis, others heard or read about its contents at second hand. What they made of it depended upon what was already in their minds; and however direct or indirect their knowledge of the book, almost everyone modified or misunderstood Harvey's doctrine. Such misunderstandings are basic to the processes by which a consensus came about and to its nature once formed.

As we saw in the last chapter, personal communication played a large part in people's knowledge of new works in natural philosophy. Gassendi read De motu cordis in the year after it was published. He thought the doctrine of circulation was attractive, but accepted the medical view that the septum between the ventricles of the heart was porous. The heart could not therefore work as Harvey had claimed. Gassendi sent his opinions to Mersenne. Mersenne in turn discussed the topic with Descartes, who seems to have read the book by 1632. Mersenne was at the centre of a circle of correspondence concerned primarily with philosophical issues. Safe postal systems had been developing in Europe over the previous century and now allowed a comparatively rapid means of communication, by letters and the dispatch of books.

Descartes was familiar with De motu cordis by the end of 1632. He too modified Harvey's doctrine. This modification is doubly important for the story of this book.