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Descartes’s Substance Dualism vs Frankish’s Illusionism

Descartes’s Substance Dualism and Frankish’s Illusionism, compared field by field from their entries in the Atlas.

At a glance

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Dualism Descartes’s Substance Dualism René Descartes
Materialism Frankish’s Illusionism Keith Frankish

The claim

In brief
Descartes’s Substance DualismRené Descartes holds that consciousness, which he calls thought (cogitatio), is the essence of an immaterial thinking substance (res cogitans) wholly distinct from extended, mechanical body (res extensa). Every conscious state, from reasoning and willing to pain, color, and emotion, is a mode of the thinking thing and is immediately present to it. Sensations and passions, though, arise only in the union of mind and body, where brain processes stand in regular relations to experiences they do not resemble.
Frankish’s IllusionismKeith Frankish holds that conscious experiences are real but not what they seem: the irreducibly subjective ‘phenomenal properties’ or qualia we ascribe to them are an introspective illusion. Introspection builds a simplified, schematic model of the brain’s complex reactions to stimulation, and we mistake that model for direct awareness of inner qualities, so the hard problem gives way to an ‘illusion problem’.
What consciousness is
Descartes’s Substance DualismConsciousness is thought, defined as everything that happens within us insofar as we are immediately conscious of it, and it is the principal attribute of the mind.
Frankish’s IllusionismConscious states are complex functional states of the brain that sustain rich sensory engagement with the world and flexible control of behavior. Their distinctive features are functional, which Frankish calls quasi-phenomenal properties.

Big questions

Can AI be conscious?Differ
Descartes’s Substance DualismNoSince thought belongs only to immaterial substance and matter is pure extension, a machine, however complex, would be mechanism without a mind.
Frankish’s IllusionismPossibleSince consciousness is a complex functional state, a system with the right reactive and sensory organization could have it, though Frankish does not address machines directly.
Does consciousness survive death?Differ
Descartes’s Substance DualismYesDescartes presented the real distinction of soul and body as what makes the soul’s survival intelligible, and the Meditations announce that aim in their subtitle.
Frankish’s IllusionismNoSince conscious states are functional states of a living brain, they end when the brain stops functioning.
Could a mind be uploaded?
Descartes’s Substance DualismNoCopying the body’s mechanism would not copy the immaterial thinking substance.
Frankish’s IllusionismNo position
Does it give life meaning?Differ
Descartes’s Substance DualismCosmic/UltimateDescartes’s system rests on a non-deceiving God who guarantees knowledge and created even the eternal truths.
Frankish’s IllusionismHumanistic onlyFrankish grounds value in what creatures are motivated to seek or avoid and argues that illusionism widens ethical concern to other animals across a graded ‘consciousness space’.

Nature of mind

Ontology
Descartes’s Substance DualismSubstance dualism (Cartesian)
Frankish’s IllusionismPhysicalism (strong illusionism)
Mind and body
Descartes’s Substance DualismMind and body are really distinct finite substances with exclusive essences, thought and extension, and could by divine power exist apart. They are joined in the human being, where bodily motions give rise to sensations and the mind moves the body, though Descartes never explained that interaction satisfactorily.
Frankish’s IllusionismConscious experiences are physically realized functional states. Phenomenal properties are intentional objects, represented but never instantiated, like the impossible objects Nicholas Humphrey compares them to.
Fundamental or emergent
Descartes’s Substance DualismPrimitive
Frankish’s IllusionismEmergent
Qualia
Descartes’s Substance DualismSensory qualities are not properties of matter, which has only size, shape, motion, and arrangement. Experienced redness or pain is a mental mode arising in the embodied union and cannot be captured by extension.
Frankish’s IllusionismQualia do not exist. Introspection misrepresents brain states, as perception misrepresents some features of the world, and introspective information bound to perception makes external things seem to carry vivid sensory qualities, such as an apple’s redness, that reflect their significance for us.

How it works

Mechanism
Descartes’s Substance DualismMechanism on the bodily side and non-reduction on the mental side. Light mechanically affects eyes, nerves, and brain, and the mind then experiences color, distance, and shape in regular correspondence with those motions.
Frankish’s IllusionismThe reactivity schema: introspective systems track the overall psychological impact of stimulation without representing its detail, and this simplified model is mistaken for direct acquaintance with qualities. Frankish borrows Daniel Dennett’s image of a computer’s user illusion, whose icons have no literal counterparts in the machine.
Where it is
Descartes’s Substance DualismThe mind is unextended. Sensations and passions are felt as belonging to one’s own body, and Descartes located mind-brain communication in the pineal gland.
Frankish’s IllusionismDistributed across the brain. The subject of the illusion is the whole organism, and the work of registering and reacting to it is shared among many unconscious subsystems, with no Cartesian theater.
What it does
Descartes’s Substance DualismPassions are caused and strengthened by movements of the animal spirits and dispose the soul toward volition and action. The will can in turn move the body.
Frankish’s IllusionismConscious states guide flexible, intelligent behavior. The illusion itself is made of physical representations and so has causal effects, which may be adaptive, as Nicholas Humphrey argues; this avoids the threat of epiphenomenalism.

Evidence and criticism

Testability
Descartes’s Substance DualismConceptually testable
Frankish’s IllusionismConceptually testable
Tests so far
Descartes’s Substance DualismNot stated
Frankish’s IllusionismFrankish holds that the reactive changes constituting experience are in principle experimentally detectable, which opens the experiences of other creatures to study.
Criticisms
Descartes’s Substance DualismPrincess Elisabeth of Bohemia asked how an immaterial soul could move a material body, and the interaction problem remains unresolved. Arnauld and later critics charged circularity, since the proofs of God that guarantee clear and distinct perception themselves rely on clear and distinct perception. The standard reading denies consciousness to animals, which most now find implausible.
Frankish’s IllusionismThe central objection, a version of Descartes’ cogito, holds that our own phenomenal states are indubitable data. Galen Strawson argues that illusionism denies the main source of ethical value. Others object that an illusion needs an audience.

Sources

Key sources
Descartes’s Substance Dualism
  • Meditations on First Philosophy, René Descartes (trans. J. Cottingham, R. Stoothoff, and D. Murdoch) (1984)
  • Principles of Philosophy, René Descartes (trans. J. Cottingham, R. Stoothoff, and D. Murdoch) (1985)
  • The Passions of the Soul, René Descartes (trans. J. Cottingham, R. Stoothoff, and D. Murdoch) (1985)
Frankish’s Illusionism
  • Frankish’s Illusionism (Landscape of Consciousness), Keith Frankish (2021)

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