Head to head
Dennett’s Illusionism vs Spinoza’s One Reality
Dennett’s Illusionism and Spinoza’s One Reality: Embodied Mind and Graded Consciousness, compared field by field from their entries in the Atlas.
At a glance
- Dennett’s Illusionism belongs to the Materialism family in Kuhn's Landscape of Consciousness, Spinoza’s One Reality to Neutral Monism.
- Dennett’s Illusionism treats consciousness as emergent; Spinoza’s One Reality treats it as fundamental.
- They give the same kind of answer on AI consciousness.
- On meaning and purpose, Dennett’s Illusionism says “Humanistic only” and Spinoza’s One Reality says “Cosmic/Ultimate”.
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The claim
In brief
Dennett’s IllusionismDaniel Dennett argues that qualia, conceived as intrinsic, ineffable, private, and immediately known properties of experience, do not exist; they are philosophers’ inventions. Experience is real, but it is not what it seems from the inside: the brain’s unconscious processes produce a benign ‘user illusion’, and there is nothing to consciousness beyond the functions and dispositions involved.
Spinoza’s One RealityBaruch Spinoza holds that there is only one substance, God or Nature, known to us under two attributes, thought and extension. A human mind is the idea of an actually existing human body: one and the same thing as the body, conceived under thought. Because every body has a corresponding idea, mind runs through all of nature, and consciousness varies by degree with the complexity and power of the body.
What consciousness is
Dennett’s IllusionismConsciousness is the functional activity of the brain, which presents itself to us as a user illusion. ‘There are no qualia.’
Spinoza’s One RealityThe mind is the idea of the body, the same individual conceived under the attribute of thought rather than extension. Spinoza does not single out phenomenal consciousness as a category; his interpreters read consciousness as higher-order awareness, cognitive access, power or complexity of thinking, or affective awareness.
Big questions
Can AI be conscious?Both agree
Dennett’s IllusionismPossibleSince consciousness is nothing beyond functions and dispositions, a machine with the right functional organization could have it; Dennett does not take this up here.
Spinoza’s One RealityConditionalSince every body has a corresponding mind whose richness tracks the body's complexity and power, a sufficiently complex artificial body would have a correspondingly rich mind; whether that mind would be conscious in the human sense is contested.
Dennett’s IllusionismNoSince consciousness is a product of the brain’s processes, it ends when they end.
Spinoza’s One RealityNo position
Dennett’s IllusionismHumanistic onlyDennett’s materialism, and his place among the New Atheists, leave no room for cosmic purpose.
Spinoza’s One RealityCosmic/UltimateMinds are modes of God or Nature, and freedom lies in understanding the causal order of Nature through more adequate ideas.
Nature of mind
Ontology
Dennett’s IllusionismPhysicalism (illusionist)
Spinoza’s One RealitySubstance monism (dual-attribute)
Mind and body
Dennett’s IllusionismConsciousness is wholly a product of the brain’s unconscious processes. Dennett rejects any inner, non-physical domain of felt properties.
Spinoza’s One RealityMind and body neither interact nor merely correlate; they are one thing under two descriptions. ‘The order and connection of ideas is the same as the order and connection of things’ (Ethics 2p7), so thought is explained only through thought and extension only through extension.
Fundamental or emergent
Dennett’s IllusionismEmergent
Spinoza’s One RealityPrimitive
Qualia
Dennett’s IllusionismThere are no qualia in the traditional sense. Dennett calls the supposed intrinsic, ineffable, private properties ‘nothing but philosophers’ inventions’.
Spinoza’s One RealitySpinoza has no explicit theory of phenomenal character. Interpreters reconstruct it from his accounts of sensation, imagination and affect, where an affect is both a change in the body's power of acting and the idea of that change.
How it works
Mechanism
Dennett’s IllusionismThe user illusion. As a computer’s desktop icons stand in for complex underlying processes, the brain presents itself to us in a simplified form we mistake for an inner world of qualities.
Spinoza’s One RealityPsychophysical identity under parallel attributes: whatever happens in the body as extension happens in the mind as an idea, so no causal bridge between them is needed.
Where it is
Dennett’s IllusionismIn the brain’s unconscious processes, with no inner theater.
Spinoza’s One RealityMentality is everywhere in nature, since all individuals are ‘animate’ in some degree (2p13s). Whether this means every physical thing has phenomenal experience is contested, and Spinoza does not treat God or Nature as one human-like conscious subject.
What it does
Dennett’s IllusionismThe user illusion is benign: it lets us manage ourselves without access to the brain’s underlying complexity.
Spinoza’s One RealityMind never causes bodily motion and body never causes thought. Affects make ideas matter to behavior by increasing, decreasing or fixing the mind's striving, and freedom comes from forming more adequate ideas of the causes acting on us.
Evidence and criticism
Testability
Dennett’s IllusionismConceptually testable
Spinoza’s One RealitySpeculative
Tests so far
Dennett’s IllusionismNot stated
Spinoza’s One RealityNot stated
Criticisms
Dennett’s IllusionismDennett is often read as denying that experience exists, and critics reply that an illusion of experience would itself be an experience. Dennett resisted the eliminativist label, though many philosophers apply it to his rejection of qualia.
Spinoza’s One RealityThe identity formula says mind and body are one thing but not what makes the thought side felt. The ideas-of-ideas reading makes every idea conscious, which Bennett called absurdly excessive, and LeBuffe notes that a mind's overall power and the power of its ideas can diverge, giving odd verdicts on degrees.
Sources
Key sources
Dennett’s Illusionism
- Consciousness Explained, Daniel Dennett
- I've Been Thinking, Daniel Dennett (2023)
- Dennett’s Illusionism (Landscape of Consciousness), Daniel Dennett (1992)
Spinoza’s One Reality
- Ethics, Baruch Spinoza (E. Curley, Ed. and Trans., The Collected Works of Spinoza) (1677)
- Spinoza’s Metaphysics: An Essay in Interpretation, E. Curley (1969)
- A Study of Spinoza's Ethics, J. Bennett (1984)