Descartes: A Biography

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 Descartes: A Biography

actions, between (a) what he called the ‘purely mechanical and bodily

principle which depends exclusively on the force of animal spirits and the

structure of the body’ (v.), and which could be called a ‘bodily soul’,

and (b) ‘the incorporeal principle or mind, or that soul that I defined

as a thinking substance’ (v.). Evidently, Descartes had extended the

scope of the first of these principles so that it functioned as an explanation

of nearly all the activities of human beings, apart from thinking. The

question about animals, then, was whether one needed to postulate a

thinking substance in order to explain their activities. Descartes thought

not. However, he also conceded that we cannot prove that there is no

thought in the strict sense of the term in animals. Rather, when he examined

‘what is most probable in this context’ he found no reason in support of

thought in animals. He could appreciate the reasons for thinking that they

have sensations that are similar to ours, but there was one outstanding

reason for resisting the idea that they have genuine thoughts. ‘It has never

been observed to date that any brute animal has achieved such a degree of

perfection that it used genuine speech, that is, that it indicated anything

by voice or signs which could be referred exclusively to thought rather

than a natural impulse’ (v.).

More’s further queries about the nature of the body and its definition

in terms of extension raised very few new questions. Descartes retained

his conception of God and angels as powers rather than as bodies of an

unusual kind. It was an important clarification of the direction in which

this argument was developed: we conceive of our own minds more easily

and more readily than we conceive of God, and we can conceive of the

latter only by analogy with the former. Even the way in which God moves

bodies can be conceived only by analogy with the way in which a human

mind, inexplicably, moves a body. ‘I concede that I find no idea in my mind,

which represents the way in which God or an angel can move matter, which

differs from that which shows me the way in which I am conscious of being

able to move my body by my thought.’

Descartes wrote these lines, in haste, in the middle of April,excus-

ing himself to More by saying that he would prefer to write quickly and

inadequately rather than fail in courtesy by not replying at all. In the

course of his reply he referred to his on-going research on animals, which

was required for completion of what he called his ‘philosophy’ (i.e., the

Principles). He was not certain that the results of his work would ever ‘see

the light of day’ (v.). However, he hoped to publish during the summer