Head to head
Higher-Order Thought Theory vs Searle’s Biological Naturalism
Rosenthal’s Higher-Order Thought and Searle’s Biological Naturalism, compared field by field from their entries in the Atlas.
At a glance
- Both belong to the Materialism family in Kuhn's Landscape of Consciousness.
- Both treat consciousness as emergent.
- They give the same kind of answer on AI consciousness, life after death and meaning and purpose.
- On mind uploading, Higher-Order Thought Theory says “Possible” and Searle’s Biological Naturalism says “Yes”.
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The claim
In brief
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.
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
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.
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?Both agree
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.
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?Both agree
Higher-Order Thought TheoryNoConscious states are natural states of an organism, so nothing remains conscious once those states stop occurring.
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.
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.
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?Both agree
Higher-Order Thought TheoryHumanistic onlyThe theory is a naturalistic account of mental states and carries no cosmic purpose.
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
Higher-Order Thought TheoryPhysicalism (naturalistic functionalism)
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
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.
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
Higher-Order Thought TheoryEmergent
Searle’s Biological NaturalismEmergent
Qualia
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.
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
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.
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
Higher-Order Thought TheoryNot stated
Searle’s Biological NaturalismLocalized in the biological brain, specifically realized in the brain as higher-level or system features.
What it does
Higher-Order Thought TheoryNot stated
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
Higher-Order Thought TheoryConceptually 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
Higher-Order Thought TheoryNot 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
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.
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
Higher-Order Thought Theory
- Rosenthal’s Higher-Order Thought, Landscape of Consciousness, David Rosenthal (2005)
Searle’s Biological Naturalism
- The Rediscovery of Mind (1992)
- Biological naturalism (2007)
- What things are conscious? (2007)
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