Head to head
Epiphenomenalism vs Higher-Order Thought Theory
Epiphenomenalism Theory and Rosenthal’s Higher-Order Thought, compared field by field from their entries in the Atlas.
At a glance
- Epiphenomenalism belongs to the Dualism family in Kuhn's Landscape of Consciousness, Higher-Order Thought Theory to Materialism.
- Both treat consciousness as emergent.
- They give the same kind of answer on life after death and meaning and purpose.
- On AI consciousness, Epiphenomenalism says “Likely” and Higher-Order Thought Theory says “Possible”.
- On mind uploading, Epiphenomenalism says “Likely” and Higher-Order Thought Theory says “Possible”.
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The claim
In brief
EpiphenomenalismThis theory posits that consciousness is a non-reducible product of the biological brain, but mental states have absolutely no causal power over physical reality. Our subjective awareness is real, yet our perception that our thoughts cause actions is mistaken, as consciousness is entirely inert, like foam on an ocean wave.
Higher-Order Thought TheoryDavid Rosenthal holds that a mental state is conscious when its subject has a higher-order thought that he or she is in that state, a thought that need not itself be conscious and does not seem to rest on inference. Mental qualities such as the redness of a sensation exist whether or not they are conscious; Rosenthal explains them separately, by how they map the perceptible properties we can discriminate.
What consciousness is
EpiphenomenalismConsciousness is identified as phenomenal properties that are ontologically distinct from physical properties but are causally dependent on them (Physical → Phenomenal).
Higher-Order Thought TheoryA state’s being conscious consists in the subject being aware of it by way of a suitable higher-order thought that one is in that state.
Big questions
Can AI be conscious?Differ
EpiphenomenalismLikelyIf consciousness is merely a non-causal byproduct (foam) of physical processes in the brain , replicating those physical processes in AI should produce the same conscious states without the non-causal mental states hindering functional replication.
Higher-Order Thought TheoryPossibleSince consciousness depends on having suitable higher-order thoughts about one’s own states, a system able to form such thoughts would meet the condition in principle.
Does consciousness survive death?Both agree
EpiphenomenalismNoConsciousness is entirely physical and solely the product of biological brains. This physical dependence precludes survival beyond bodily death.
Higher-Order Thought TheoryNoConscious states are natural states of an organism, so nothing remains conscious once those states stop occurring.
EpiphenomenalismLikelyThe inert nature of consciousness means that uploading the physical states would necessarily duplicate the epiphenomenal mental states. The inert 'foam' should have little impact on achieving virtual immortality.
Higher-Order Thought TheoryPossibleIf the relevant first-order states and higher-order thoughts were reproduced, the view gives no principled reason the copy would lack consciousness.
Does it give life meaning?Both agree
EpiphenomenalismHumanistic onlyAs a philosophical materialism theory, it provides no ultimate meaning or purpose. Since consciousness is causally inert, it cannot confer cosmic teleological value.
Higher-Order Thought TheoryHumanistic onlyThe theory is a naturalistic account of mental states and carries no cosmic purpose.
Nature of mind
Ontology
EpiphenomenalismWeak form of Dualism or Non-Reductive Physicalism. It affirms the complete causal closure of the physical.
Higher-Order Thought TheoryPhysicalism (naturalistic functionalism)
Mind and body
EpiphenomenalismMental states are entirely the product of biological brains. Physical states cause phenomenal states, but phenomenal states have no causal effect on the physical (one-directional causation).
Higher-Order Thought TheoryMental states, their qualities, and the higher-order thoughts that make them conscious are all natural states of the organism; Rosenthal expects neural correlates of consciousness to be whatever mechanism produces the higher-order awareness.
Fundamental or emergent
EpiphenomenalismEmergent. Consciousness is solely the product of biological brains.
Higher-Order Thought TheoryEmergent
Qualia
EpiphenomenalismPhenomenal properties (qualia) are real and ontologically distinct from physical properties , but they are epiphenomena and thus causally inert.
Higher-Order Thought TheoryMental qualities are fixed by their role in perceptual discrimination and occupy a ‘quality space’ that mirrors the similarities among perceptible properties. Because these qualities do not depend on consciousness, a sensation can have qualitative character without being conscious, as in subliminal perception.
How it works
Mechanism
EpiphenomenalismThe principle of the 'causal closure of the physical' dictates that mental states, whatever their nature, must be entirely inert byproducts.
Higher-Order Thought TheoryA non-inferential higher-order thought that one is in a given state, which makes that first-order state conscious even when the thought itself is unconscious.
Where it is
EpiphenomenalismEntirely located in the physical, biological brain.
Higher-Order Thought TheoryNot stated
What it does
EpiphenomenalismMental states have no causal powers. The mind is entirely inert and there is no 'top-down causation'; consciousness is a non-functional byproduct.
Higher-Order Thought TheoryNot stated
Evidence and criticism
Testability
EpiphenomenalismConceptually challenged. Its primary claim—that conscious states lack causal force—is counterintuitive and difficult to test empirically, as it involves proving a negative causal link.
Higher-Order Thought TheoryConceptually testable
Tests so far
EpiphenomenalismNot stated
Higher-Order Thought TheoryNot stated
Criticisms
EpiphenomenalismThe theory is counterintuitive because it strongly seems to us that our phenomenally conscious states causally matter. It forces the acceptance that our sense of mental causation (thoughts causing things) is a 'kind of illusion or trick'.
Higher-Order Thought TheoryFirst-order theorists argue that higher-order awareness is an unneeded extra ingredient, and deflationists say being aware of a conscious state is like ‘smiling a smile’. Rosenthal replies that a deflated awareness cannot explain the contrast between conscious and unconscious states.
Sources
Key sources
Epiphenomenalism
- Consciousness (2019)
- Facing up to the Problem of Consciousness (1995)
- What Is Consciousness? (Little Debates about Big Questions), A. Kind and D. Stoljar (2023)
Higher-Order Thought Theory
- Rosenthal’s Higher-Order Thought, Landscape of Consciousness, David Rosenthal (2005)