Head to head
Descartes’s Substance Dualism vs Free Energy Principle
Descartes’s Substance Dualism and Friston’s free-energy principle and active inference, compared field by field from their entries in the Atlas.
At a glance
- Descartes’s Substance Dualism belongs to the Dualism family in Kuhn's Landscape of Consciousness, Free Energy Principle to Materialism.
- Descartes’s Substance Dualism treats consciousness as fundamental; Free Energy Principle treats it as emergent.
- On AI consciousness, Descartes’s Substance Dualism says “No” and Free Energy Principle says “Yes”.
- On life after death, Descartes’s Substance Dualism says “Yes” and Free Energy Principle says “No”.
- On mind uploading, Descartes’s Substance Dualism says “No” and Free Energy Principle says “Yes”.
- On meaning and purpose, Descartes’s Substance Dualism says “Cosmic/Ultimate” and Free Energy Principle says “Humanistic only”.
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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.
Free Energy PrincipleThis theory conceptualizes consciousness as a natural process arising from the minimization of 'free energy,' which is the difference between an organism's internal model (perceptual expectations) and real-time sensory inputs. Consciousness, therefore, functions as the evolved mechanism for simulating scenarios of the world and reducing prediction error to ensure survival and maintain homeostasis.
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.
Free Energy PrincipleConsciousness is identified as a natural process of inference, specifically the internal emergent model that monitors and minimizes the free energy principle (surprise), thereby optimizing the representational capacities of physical/brain systems.
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.
Free Energy PrincipleYesAs a strong materialist theory, if consciousness is fully explained by computational processes of inference and representation minimization, then non-biological systems capable of executing these processes must eventually attain consciousness in principle.
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.
Free Energy PrincipleNoConsciousness is an emergent natural process tied directly to the functional dynamics and physical substrate of the biological brain; thus, it cannot survive bodily decay.
Descartes’s Substance DualismNoCopying the body’s mechanism would not copy the immaterial thinking substance.
Free Energy PrincipleYesSince consciousness is understood as an emergent, formalized process of inference optimization, perfect duplication of the brain's information processing and representational dynamics in a non-biological medium should be sufficient for the continuation of the mental self.
Descartes’s Substance DualismCosmic/UltimateDescartes’s system rests on a non-deceiving God who guarantees knowledge and created even the eternal truths.
Free Energy PrincipleHumanistic onlyThe foundational imperative of the conscious process is survival (minimizing surprise/maintaining homeostasis). The theory does not rationalize ultimate cosmic meaning or purpose, aligning with general materialist perspectives.
Nature of mind
Ontology
Descartes’s Substance DualismSubstance dualism (Cartesian)
Free Energy PrinciplePhysicalism; often referred to as Markovian Monism, which views mind/matter distinction as dialectical rather than ontological.
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.
Free Energy PrincipleMonistic/Identity. The theory proposes that consciousness is the natural outcome of the physical/brain system's self-organizing processes, dissolving familiar dialectics between mind and matter.
Fundamental or emergent
Descartes’s Substance DualismPrimitive
Free Energy PrincipleEmergent
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.
Free Energy PrincipleThe theory is highly deflationary regarding the Hard Problem, treating consciousness as a process to be understood rather than a 'thing' whose qualitative attributes need definition. Qualia, if acknowledged, would be epiphenomena or aspects of the internal generative model required for inference.
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.
Free Energy PrincipleThe Free-Energy Principle (FEP), which states that all self-organizing systems must minimize free energy (or 'surprise'), driving action and perception through active inference.
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.
Free Energy PrincipleLocalized in the physical brain system; cortical responses are seen as the brain’s attempt to minimize free energy.
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.
Free Energy PrincipleConsciousness serves an adaptive and functional role as the evolved mechanism for simulating scenarios, monitoring, and minimizing free energy to promote survival (homeostasis) and navigate the world.
Evidence and criticism
Testability
Descartes’s Substance DualismConceptually testable
Free Energy PrincipleConceptually and empirically linked to testable models (e.g., in neurobiology and psychology) through its reliance on formalizing representational capacities of physical systems.
Tests so far
Descartes’s Substance DualismNot stated
Free Energy PrincipleThe principles of FEP form the basis for models utilized in empirical work concerning altered states (e.g., the Entropic Brain Hypothesis under psychedelics) and related theories of perception and cognition.
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.
Free Energy PrincipleCriticized for being highly deflationary and difficult to reconcile with the first-person reality of phenomenal experience (the Hard Problem), viewing consciousness merely as a mathematical process or 'natural outcome.' Friston finds engaging with the philosophical premise of consciousness as a 'thing' difficult.
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)
Free Energy Principle
- A theory of cortical responses, K. Friston (2005)
- Active interference: a process theory, K. Friston et al (2017)
- The Mathematics of Mind-Time, K. Friston (2017)
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