Descartes: A Biography

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 Descartes: A Biography

immobilizing chickens, and observations of the development of chickens

in eggs.He even arranged for the slaughter of a pregnant cow so that

he could examine the foetus at an early stage of its development. When

he noticed that Dutch butchers often slaughtered pregnant cows, he took

advantage of their carelessness to further his investigations: ‘I arranged

forthem to bring me more than a dozen wombs in which there were small

calves, some as big as mice, others as big as rats, and others again like small

dogs, in which I could observe many more things than was possible in the

case of chickens because their organs are larger and more visible’ (iv.).

This on-going work in anatomy coincided with the Marquis of

Newcastle’s interest in the apparent capacity of animals to think. Unfor-

tunately, when Cavendish wrote to Descartes to ask his opinion about

the matter, his letter took ten months to arrive in Egmond-Binnen.

Despite the delay, Descartes took the question seriously and, in the pro-

cess, wrote one of his clearest comments yet on whether animals are capable

of thinking.

This question developed naturally from the theories that Descartes

had been exploring in theTreatise on Manin thes.He had argued

then that many features of human perception, imagination, memory, and

intentional action are explained by reference to the flow of animal spir-

its in the nerves. He assumed, of course, that many nonhuman animals

have similar brains and that the complex ways in which they react to their

environments must be explained in the same way. Thus when he offered

readers a summary of the contents of that (unpublished)Treatisein the

Discourse on Method,hetook advantage of the opportunity to make as clear

a distinction as possible between human beings and other animals. The

significance of the question at issue could hardly be exaggerated. The the-

ology of the Christian churches depended on the assumption of a life after

death, in which sin is punished and a virtuous life is rewarded. For many

Christians, those beliefs presuppose that each person has an immortal

soul. By contrast, the behaviour of animals – no matter how sophisticated

it may be – can be explained without attributing an immortal soul to them.

Newcastle’s question thus reopened the metaphysical questions that had

been addressed in theMeditations, where Descartes had tried to establish

‘the distinction between the human soul and the body’.

Descartes’ account of human nature, in theDiscourse, was not much

different from what he wrote seven years later in thePrinciples.Hehad to

concede in theDiscoursethat, when he discussed human nature, he ‘did