Descartes: A Biography

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 Descartes: A Biography

(i.). The other, more familiar reason was that his progress was slower

than expected. He was ashamed to say that what he had written so far was

hardly more than about half the length of his letter to Mersenne (i.e., about

ten pages), and that the expected completion date was slipping further into

the future.

One gets a good idea of the range of questions that were to be included

in this treatise from Descartes’ correspondence during the years of its

composition. The law of falling bodies, the dissemination of sound, an

explanation of condensation, the optics of mirrors, and generally all of

the properties that are usually attributed to physical bodies, are all dis-

cussed at various stages of composition. The sources of the questions are

equally varied. In the course of thanking Mersenne for providing a list from

Aristotle of properties that required explanation, Descartes acknowledged

that he had also drawn up a list himself, ‘partly derived from Verulamius

[Francis Bacon] and partly from my own head’ (i.). Not only was he

reading Bacon, but he had also dipped into Kepler’s work on snow and

had asked whether Gassendi might have any further comments to make

onthe same subject.He had hoped to do further observations on mete-

orological phenomena, although an unusually warm winter had made it

impossible to do any empirical research on ice or snow.

Descartes also began serious work in anatomy at this time. He described

his investigations, nine years later, in a letter to Mersenne (November

):

It is not a crime to be interested in anatomy. I spent one winter in Amsterdam during

which I used to go almost every day to the butcher’s house to see him kill the animals,

and I used to take home with me the parts that I wanted to dissect with more leisure.

Ihavedonethe same thing on many occasions in all the places where I lived, and I do

not think that any intelligent person could blame me for that. (ii.)

This work is reflected in the detailed references to an ox’s eye in the

Dioptrics, and in later correspondence with Mersenne.

During this whole period of almost a year from his initial arrival in

the United Provinces, Descartes continues to be excessively careful about

concealing his address. He tells Mersenne that he is not concerned if

people speculate about where he lives, provided that his exact location is

not revealed.In March,heencourages Mersenne to ask anyone who

remembers him whether they think he is still alive and where they think he

is living.The need for secrecy about his plans is repeated the following