Open the map

Head to head

Descartes’s Substance Dualism vs Kastrup’s Analytic Idealism

Descartes’s Substance Dualism and Analytic Idealism, 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
Idealism Analytic Idealism Bernardo Kastrup

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.
Kastrup’s Analytic IdealismAnalytic Idealism is a consciousness-only ontology asserting that phenomenal consciousness is fundamental, the singular primitive of reality. Everything else in nature, including the physical world and individual minds, is grounded in patterns of excitation or expressions of this spatially unbound cosmic consciousness.
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.
Kastrup’s Analytic IdealismConsciousness is identified as the singular, spatially unbound, fundamental ontological primitive (cosmic consciousness).

Big questions

Can AI be conscious?Both agree
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.
Kastrup’s Analytic IdealismNoKastrup suggests conscious AI is a fantasy, arguing that consciousness is not reducible to computation or information processing that current computers perform. Consciousness is tied to fundamental phenomenal reality, not hardware function.
Does consciousness survive death?Both agree
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.
Kastrup’s Analytic IdealismLikelyBodily death is predicted to result in the cessation of the local boundary (dissociated alter), causing conscious inner life to expand back into the underlying universal consciousness. This is supported circumstantially by reports of near-death experiences (NDEs).
Could a mind be uploaded?Both agree
Descartes’s Substance DualismNoCopying the body’s mechanism would not copy the immaterial thinking substance.
Kastrup’s Analytic IdealismNoConsciousness is not an algorithm or software program reducible to physical structure; therefore, uploading neural patterns (simulated continuation) would only result in a functional duplication ('deep fake') lacking true subjective experience.
Does it give life meaning?Both agree
Descartes’s Substance DualismCosmic/UltimateDescartes’s system rests on a non-deceiving God who guarantees knowledge and created even the eternal truths.
Kastrup’s Analytic IdealismCosmic/UltimateAs consciousness is ultimate reality, existence is fundamentally grounded in mind/awareness, intrinsically providing meaning and purpose rooted in the singular, fundamental consciousness.

Nature of mind

Ontology
Descartes’s Substance DualismSubstance dualism (Cartesian)
Kastrup’s Analytic IdealismIdealism (Modern analytic metaphysics)
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.
Kastrup’s Analytic IdealismIndividual minds are dissociated alters of the cosmic consciousness. The inanimate physical world is the extrinsic view of thoughts and emotions within this universal consciousness, meaning a physical world independent of consciousness is a mistaken intellectual abstraction.
Fundamental or emergent
Descartes’s Substance DualismPrimitive
Kastrup’s Analytic IdealismPrimitive (Fundamental)
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.
Kastrup’s Analytic IdealismQualia are intrinsically real and fundamental, constituting patterns of excitation within the fundamental phenomenal consciousness.

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.
Kastrup’s Analytic IdealismThe principle of dissociation, which localizes the unitary cosmic consciousness into seemingly isolated subjects (alters).
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.
Kastrup’s Analytic IdealismUbiquitous; consciousness is fundamental and spatially unbound. Individual conscious subjects are localized boundary conditions (dissociated alters).
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.
Kastrup’s Analytic IdealismCausation is grounded in consciousness itself. The inanimate world is the extrinsic manifestation of universal mentation, while the brain serves to constrain or mediate individual consciousness.

Evidence and criticism

Testability
Descartes’s Substance DualismConceptually testable
Kastrup’s Analytic IdealismSpeculative/Conceptual. Testable primarily by demonstrating the incoherence or lack of parsimony of rival metaphysical theories and by predicting experiential outcomes in extreme states.
Tests so far
Descartes’s Substance DualismNot stated
Kastrup’s Analytic IdealismCites neuroimaging of psychedelic states (rich experience correlating with reduced brain activity) to critique physicalist theories.
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.
Kastrup’s Analytic IdealismThe main critical challenge is the 'decomposition problem': explaining how seemingly distinct phenomenal inner lives of subjects can arise within a fundamentally unitary phenomenal field. Also must reconcile the independence of the common external world from personal volition.

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)
Kastrup’s Analytic Idealism
  • An ontological solution to the mind-body problem (2017)
  • The universe in consciousness (2018)
  • Analytic Idealism: A Consciousness-Only Ontology, Dissertation (2019)

More comparisons

Descartes’s Substance Dualism vs …

Kastrup’s Analytic Idealism vs …

All head-to-head comparisons →