This is part of an ongoing project whose modest goal is to nuance the understanding of humanism in posthumanist philosophy and criticism. Cartesian dualism is one of the main targets of these critiques, but differences between dualisms tend to become obscured in the rush to lay the liberal humanist subject. Here, I’m using Mike Wheeler’s discussion of the Cartesian roots of mainstream cognitive science in Reconstructing the Cognitive World to distinguish between substance dualism (which nobody seems to believe) and explanatory dualism – arguably the orthodoxy in philosophy of psychology, from Kant to Fodor and beyond.
In a much-discussed passage from the fifth part of The Discourse on Method Descartes supports his dualist metaphysics with what we might call the “argument from the impossibility of artificial intelligence”. He claims that no machine (i.e. a biomechanical system such as an animal body) could act in the flexible, adaptable and generally rational way that ordinary humans do:
[We] may easily conceive a machine to be so constructed that it emits vocables, and even that it emits some correspondent to the action upon it of external objects which cause a change in its organs; for example, if touched in a particular place it may demand what we wish to say to it; if in another it may cry out that it is hurt, and such like; but not that it should arrange them variously so as appositely to reply to what is said in its presence, as men of the lowest grade of intellect can do. The second test is, that although such machines might execute many things with equal or perhaps greater perfection than any of us, they would, without doubt, fail in certain others from which it could be discovered that they did not act from knowledge, but solely from the disposition of their organs: for while reason is an universal instrument that is alike available on every occasion, these organs, on the contrary, need a particular arrangement for each particular action; whence it must be morally impossible that there should exist in any machine a diversity of organs sufficient to enable it to act in all the occurrences of life, in the way in which our reason enables us to act. (Descartes 1985, 44).
To ape rationality a mechanical system would need to integrate special purpose mechanisms suited to every occasion (a “look up table” in computational terms – see Wheeler 2005, 34). Since these occasions could ramify to infinity a mechanical system that could generate reliably appropriate behaviour would require a practically infinite number of parts.
In “Theorizing Posthumanism” Neil Badmington reads this as an attempt to police an ontological blockade between the human being and the nonhuman animal. However, in a textbook deconstructive move he claims that its formulation undermines its declared intent. For by identifying the capacity for reasoning with the functional capacity for context sensitive performance, Descartes allows for the conceptual possibility of a machine so complex that it would have an arrangement for every possible occasion – in effect, running an infinite look-up table.
Descartes’ anthropocentrism is thus less hygienic and secure than it might appear, for it implies that a material system with the complexity to generate flexible performances would be functionally rational. “Reason” Badmington writes “no longer capable of “distinguish[ing] us from the beasts, would meet its match, its fatal and flawless double.” (Badmington 2003, 18). He then springs his coup de théâtre:
On closer inspection, in other words, there lies within Descartes’s ontological hygiene a real sense in which, to take a line from one of Philip K. Dick’s novels, “[l]iving and unliving things are exchanging properties” (1996, 223; emphasis in original). Between the lines of the text, the lines of humanism cross themselves (out), and the moment at which humanism insists becomes the moment at which it nonetheless desists. Quite against his will, quite against all odds, Descartes has begun to resemble Deckard, the troubled protagonist of Do Androids Dream of Electric Sheep? … and Blade Runner … , who utterly fails to police the boundary between the real and the fake (Ibid.).
Casting Harrison Ford as Descartes is nice, but too quick. While Descartes may have had reasons to observe ontological hygiene precautions, in this passage, at least, he is attempting to motivate belief in a disembodied mind through inference to the best explanation. It is the manifest functional differences between humans and brutes that institutes the quarantine line, not the dualist ontology of extended matter and non-extended mind (Ryle’s “ghost in the machine”).
Descartes makes an empirical assumption about the limits of mechanical complexity in this passage (not an a priori claim about in-principle-complexity). If we think this holds, we should infer that our synapses are haunted. If we don’t, we shouldn’t. Badmington’s deconstruction requires Descartes be saddled with the assumption that rationality is a matter of appropriate functioning rather than spooked synapses. But in that case, there is a mark of the human (or at least of the rational intellect): namely, the capacity to function like humans do.
Thus we may easily ditch substance dualism while holding that an exhaustive list of the arrangements of matter responsible for each token of appropriate behaviour could not explain the capacity for flexible and rational behaviour. For one, any such account would be too vast to afford descriptive economy. More importantly, it would miss the abstract functional facts that, by hypothesis, distinguish us from the brutes. Thus, as Wheeler argues in Reconstructing the Cognitive World: The Next Step, the rejection of substance dualism is compatible with explanatory dualism: a scientific methodology that turns away from neuroscience and biomechanics to consider the inferential processes or practices which produce intelligent, flexible and adaptable behaviour. According to this view: “flexible, intelligent action remains conceptually and theoretically independent of the scientific understanding of the agent’s physical embodiment” (Wheeler 2005, 51).
Badmington, Neil (2003), “Theorizing Posthumanism”, Cultural Critique 53, 10-27,
Descartes (1985) A Discourse on Method. Trans. John Veitch. London: Everyman.
Wheeler, Michael (2005) Reconstructing the Cognitive World: the Next Step. MIT Press, 2005.