Neural Correlates of Consciousness in Descartes and Willis

null, Brian Key, Deborah Brown (University of Queensland)

Venue: online Zoom meeting

Zoom link: https://unive.zoom.us/j/84571640858?pwd=MWFJbFgxRjlnaVJLWUpIOWJwQlZVUT09

Zoom meeting ID: 845 7164 0858; Passcode: gMi180

Abstract:

For sheer volume of criticism, no doctrine of Descartes’ beats that of his denial that animals think or have feelings. Criticism came from all fronts—from behaviorists; from vitalists; and from teleologists committed to reinstating Aristotle’s “purposive efforts” in nature. These objections aside, the internal tensions within Descartes’ arguments are striking for a philosopher of his calibre. There is the infamous slippery slope argument that if we were to attribute thought (which Descartes equates with consciousness) to some animals, we’d have to attribute it to all, including oysters and sponges, and if we did that, we’d have to suppose that they all have immortal souls (AT 4: 576; CSMK: 304), an especially odd argument given that Descartes never proved that the natural soul of humans is immortal. There is also a tension between Descartes’ claim that animal behaviour is essentially inflexible, whether it be reflex or learned behaviour, and his observation that the flexibility of human behaviour is due to the plasticity of the brain, a conclusion he infers from observations of the brain structures of animals. Descartes is right to be worried about arbitrarily drawing boundaries between conscious and non-conscious organisms, but his own commitment to what was to become the foundational axiom of the biological sciences—that structure-determines-function—afforded him, at least in principle, the conceptual tools for making such discriminations. Enter Thomas Willis (1621-75), the father of neurology and comparative neurobiology. Willis embraces many of the features of Descartes’ account of nerve function—the role of the animal spirits; the role of the brain in integrating and storing sensory information in a ‘natural memory’ and issuing motor commands; and the idea that the ‘corporeal soul’ of animals is material and thus distinct from the intellectual soul of humans. Crucially, Willis also put the structure-determines-function principle to use in making non-arbitrary distinctions between conscious and non-conscious animals. This he did by observing that reflexive and associative behaviour could be wholly explained by sub-cortical structures, whereas consciously and cognitively mediated behaviour was under cortical control. Among other things, Willis thought that this should prompt a rethink of Descartes’ metaphysical assumptions about the nature of the soul. He rejected Descartes’ twin claims that no sensitive soul could be rational without being capable of intellectual abstraction and that no soul could be both rational and corporeal. Details aside, his overarching picture of the neural bases of consciousness is one that has stood the test of time, and his challenges both to Descartes’ physics and his metaphysics are worthy of a place in the philosophical canon.