Descartes on the Beast-Machine Doctrine
Lawrence Nolan (California State University, Long Beach)

March 21, 2022, 6:00pm - 8:00pm
CREMT, Ca' Foscari University, Venice



  • European Commission, Marie Sklodowska-Curie grant agreement No 892794


University of Venice
Università di Torino

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Zoom meeting ID: 845 7164 0858; Passcode: gMi180


Despite its notoriety, Descartes’s assertion that animals are mere automata—lacking reason, sensory cognition, and even bare feeling—has not received the scholarly attention that has been devoted to most of his other doctrines. As a result, several problems of interpretation remain, and the so-called beast-machine (bêtes-machine) doctrine appears to constitute an embarrassment within his larger philosophical system. In this paper, I hope to redress this situation by resolving some of the purported difficulties with the doctrine and showing how it can be defended using some of Descartes’s most basic philosophical commitments. 

One interpretative problem concerns Descartes’s boast that he can explain all animal behavior mechanistically without appeal to an immaterial soul. Critics complain that this is just an unfulfilled promissory note, given the dearth of details pertaining to specific animal behaviors. So, what exactly underwrites Descartes’s boast and why was he so confident? Furthermore, why does Descartes focus on the question of whether animals use reason, to the exclusion of other forms consciousness such as sensation? And, given this focus, how does he move from the claim that they lack reason to the more general conclusion that they lack all forms of thought?

Another question concerns Descartes’s philosophical motivations for the beast-machine doctrine. Is it inspired by his anti-scholastic conception of matter and his project of mechanizing the living body, by his novel understanding of thought, by theological concerns, or something else? A closely related issue is how he argues for the negative view of animal cognition. In Discourse V, Descartes introduces two well-known tests, which have come to be called the language test and the action test. Many readers have taken these to constitute premises in his main argument for the beast-machine doctrine, but I uncover the pitfalls in doing so. There are also problems with the tests themselves. As critics have noted, infants, idiots, and perhaps the decrepit elderly fail them, but there is strong textual evidence that Descartes does not wish to conclude that any human beings lack mentality and hence immortal souls. I argue that this and other difficulties with the two tests can be resolved by abandoning the assumption that they are intended to provide strict criteria. Passing either test constitutes a sufficient condition for consciousness but not a necessary one.

It is noteworthy that some of Descartes’s followers, such as Nicolas Malebranche and Antoine Dilly, who endorse the beast-machine doctrine tend to focus on theological arguments. Although Descartes briefly mentions an argument from immortality in his correspondence, it is puzzling why he treads lightly with such arguments. A final interpretive puzzle concerns the strength of Descartes’s position on animals. Some readers have thought that he weakens his claims over time in the face of objections, moving from declaring metaphysical certainty to “moral certainty”. To render a verdict here, one must first address the more fundamental questions about his philosophical motivations and how he argues for the beast-machine doctrine.

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