Open the map

Head to head

Descartes’s Substance Dualism vs Searle’s Biological Naturalism

Descartes’s Substance Dualism and Searle’s Biological Naturalism, compared field by field from their entries in the Atlas.

At a glance

Add more theories to this comparisonCompare other theories

Dualism Descartes’s Substance Dualism René Descartes
Materialism Searle’s Biological Naturalism John Searle

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.
Searle’s Biological NaturalismBiological Naturalism posits that consciousness is a real, irreducible, subjective biological feature of the brain, entirely caused by lower-level neurobiological processes and realized as higher-level system features. This approach seeks to solve the mind-body problem by accepting the scientific worldview while acknowledging the first-person ontology of conscious experience.
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.
Searle’s Biological NaturalismConscious states are identified as real parts of the real world that are higher-level, system features of the brain, defined as states of awareness, sentience, or feeling that persist during wakefulness.

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.
Searle’s Biological NaturalismConditionalSearle rejects consciousness via simulation (Chinese Room Argument) but argues that if the causally sufficient biological mechanism is known, an artificial machine that implements that same mechanism could be conscious, as consciousness does not strictly require biological neurons, only sufficient causal power.
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.
Searle’s Biological NaturalismNoConsciousness is entirely physical and solely the product of biological brains; therefore, death of the brain and body means irrevocable, permanent non-existence.
Could a mind be uploaded?Differ
Descartes’s Substance DualismNoCopying the body’s mechanism would not copy the immaterial thinking substance.
Searle’s Biological NaturalismYesIf consciousness is entirely explainable by physical/biological states, then duplicating those states (and their causal relations) in a non-biological medium would, in principle, allow for the uploading and continuation of the first-person mental self.
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.
Searle’s Biological NaturalismHumanistic onlyAs a materialist theory, Biological Naturalism struggles to rationalize ultimate cosmic meaning or purpose, though humanistic meaning created by ourselves remains possible.

Nature of mind

Ontology
Descartes’s Substance DualismSubstance dualism (Cartesian)
Searle’s Biological NaturalismPhysicalism (Biological Naturalism). It holds that consciousness is part of nature as a subjective, qualitative biological property, rejecting attempts to 'naturalize' it by denying its subjective ontology.
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.
Searle’s Biological NaturalismConscious states are causally reduced to lower-level brain processes (causal reducibility), but are ontologically irreducible to these processes because consciousness has a subjective (first-person) ontology while its basis has an objective (third-person) ontology.
Fundamental or emergent
Descartes’s Substance DualismPrimitive
Searle’s Biological NaturalismEmergent
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.
Searle’s Biological NaturalismConscious states are inherently qualitative, in the sense that there is a distinct qualitative feel to being in any particular conscious state, and this qualitative feel is a real and irreducible part of the world.

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.
Searle’s Biological NaturalismThe principle is that all conscious states are reliably and universally caused by lower-level brain processes and realized as system features, functioning as a real biological 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.
Searle’s Biological NaturalismLocalized in the biological brain, specifically realized in the brain as higher-level or system features.
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.
Searle’s Biological NaturalismConscious states function causally (causal efficacy) as real parts of the real world, providing a basis for intentional action and interaction with the environment.

Evidence and criticism

Testability
Descartes’s Substance DualismConceptually testable
Searle’s Biological NaturalismEmpirically testable in principle, as the theory requires finding the exact causal details of how lower-level brain processes cause consciousness.
Tests so far
Descartes’s Substance DualismNot stated
Searle’s Biological NaturalismThe theory is generally supported by empirical evidence from neuroscience showing the link between consciousness and brain activity (e.g., brain impairment, brain stimulation).
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.
Searle’s Biological NaturalismCritics dispute the claim that the causal connection between brain states and consciousness is fully established. Tension exists in maintaining materialism while arguing consciousness is ontologically subjective and irreducible to objective physical processes.

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)
Searle’s Biological Naturalism
  • The Rediscovery of Mind (1992)
  • Biological naturalism (2007)
  • What things are conscious? (2007)

More comparisons

Descartes’s Substance Dualism vs …

Searle’s Biological Naturalism vs …

All head-to-head comparisons →