Papineau’s Mind-Brain Identity

Philosopher David Papineau defends a robust neurobiological physicalism about phenomenal consciousness, in which conscious states are literally identical with brain states—not caused by them, not generated by them, not correlated with them, but the same states under a different mode of presentation. His argument has three moving parts: a causal argument that mental states must be physical, given that the physical realm is causally closed and mental states have physical effects; an abductive argument that identity, rather than mere correlation, best explains the lawlike covariation of conscious states with neural states; and a diagnostic argument that the residual sense of an explanatory gap is a cognitive illusion arising from the peculiar structure of phenomenal concepts, which he named the "antipathetic fallacy" (Papineau, 1993a, 2002). A fourth, less often noticed commitment follows: because phenomenal concepts are semantically vague, Papineau holds that there is no determinate material essence of pain or of color experience for neuroscience to discover, only a plurality of correlates among which nothing fixes a unique referent (Papineau, 2003). The argument bears on all materialist theories of consciousness (Papineau, 2020b).

One of Papineau's framing intuitions is that "there seems no immediate reason why consciousness should be singled out as posing some special puzzle about its relation to the rest of reality"—given that "reality contains many different kinds of things, biological, meteorological, chemical, electrical, and so on, all existing alongside each other, and all interacting causally in various ways" (Papineau, 2020b).

The Causal Argument and the Closure of the Physical

Papineau's route to physicalism begins not with consciousness but with causation. We feel that "conscious mind influences non-conscious matter, by controlling bodily behaviour, and similarly that matter influences mind, giving rise to sensory experiences, pains and other conscious mental states." Yet the "compelling argument … against this kind of interactionist stance … derives from the so-called 'causal closure of the physical' … the physical realm seems causally sufficient unto itself" (Papineau, 2020b).

The argument that follows is straightforward in structure. Conscious states have physical effects—we wince, we report, we withdraw the hand. Every physical effect has a sufficient physical cause. If conscious states were distinct from physical states, their effects would be systematically overdetermined, which is implausible as a general feature of the world. Therefore, conscious states are physical states (Papineau, 2002). Papineau developed the empirical case for closure at length, tracing how nineteenth- and twentieth-century physiology progressively eliminated the vital and mental forces that had once been posited to explain bodily movement. The argument's force is thus historical and scientific rather than a priori—a characteristic feature of his naturalism, which also underwrites his teleosemantic account of mental representation.

This argument establishes that conscious states are physical. It does not by itself establish that they are identical with any particular type of neural state. That further conclusion requires a different argument.

The Explanatory Gap and the Antipathetic Fallacy

Papineau observes that we remain puzzled about the relation between brain states and mental states in a way we are not puzzled about the relation between NaCl and salt, or between electrical discharge and lightning. He attributes this puzzlement—the "explanatory gap" of consciousness (Levine, 1983)—to a cognitive fact about how we deploy concepts: "we find it hard to escape the spontaneous dualist thought that the feeling and the physical state are not one thing, but two different states that somehow invariably accompany each other" (Papineau, 2020b).

He named this illusion the antipathetic fallacy, adapting Ruskin's "pathetic fallacy"—where we wrongly project feeling into inanimate nature—to its converse, where we wrongly refuse to recognize that feelings inhere in certain parts of nature, namely brains (Papineau, 1993a, 1995).

The mechanism is a peculiarity of phenomenal concepts. Unlike theoretical concepts, which pick out their referents by description, phenomenal concepts operate by using or activating a version of the experience they refer to. Thinking about the taste of chocolate makes the mouth water; an imagined pain shares some of the unpleasantness of a real one, enough to make you twitch or feel queasy. Papineau calls this a use/mention feature: each deployment of a phenomenal concept instantiates a "faint copy" of the property it denotes (Papineau, 2002, 2011).

This generates the illusion of distinctness directly. Consider "the visual experience of red = brain state B." Contemplating the left-hand side activates a trace of the experience; contemplating the right-hand side does not. The two sides of the identity therefore feel different, and we mistake a difference in how we are thinking for a difference in what we are thinking about. The reaction that such identities must be mistaken because "the phenomenology isn't captured by the right-hand side" is, on this diagnosis, a sense/reference confusion.

An insight concerns the connotation of the verbs used to describe the mind-brain relation. Brain processes are said to "generate," or "yield," or "cause," or "give rise to" conscious states. This phraseology, Papineau says, undermines physicalism from the start—even when physicalists use it. As he puts it, "Fire 'generates', 'causes', 'yields' or 'gives rise to' smoke. But NaCl doesn't 'generate', 'cause', 'yield' or 'give rise to' salt. It is salt. The point is clear. To speak of brain processes as 'generating' conscious states, and so on, only makes sense if you are implicitly thinking of the conscious states as separate from the brain states" (Papineau, 2020b).[1]

Abductive Identity and the Zombie Challenge

Because no a priori derivation is available, Papineau holds that "our knowledge of mind-brain identities can only be based on some kind of a posteriori abductive inference, rather than a principled a priori demonstration that a certain physical state fills some specified role. For example, we might observe that pains occur whenever prefrontal nociceptive-specific neurons fire, and vice versa; we might also note that, if pains were the firing of nociceptive-specific neurons, then this would account for a number of other observed facts about pain, such as that it can be caused by trapped nerves, and can be blocked by aspirin; and we might conclude on this basis that pains are indeed identical to the firing of nociceptive-specific neurons" (Papineau, 2020b).

He singles out "the peculiarly direct nature of our concepts of conscious states" as what "stops us deriving mind-brain identities a priori from the physical facts."

This is how identity claims are established generally. It "can only be on the basis of an abductive inference from direct empirical evidence, such as that the two things in question are found in the same places and the same times, and are observed to bear the same relations to other things, not because we can deduce the identities a priori from the physical facts." His examples include "Cary Grant = Archie Leach" and "that dog = her pet." "Why shouldn't this same way of thinking be applied to consciousness?" he asks (Papineau, 2020b).

Because, he answers, "even after we are given all the abductive evidence, we still find mind-brain identity claims almost impossible to believe. We cannot resist the dualist conviction that conscious feelings and the physical brain states are two different things." And this "is the real reason why we feel a need for further explanation. We want to know why the neuronal activity is accompanied by that conscious feeling, rather than by some other, or by no feeling at all. Our dualist intuitions automatically generate a hankering for further explanation."

Thus, Papineau concludes, "the demand for explanation arises, not because something is lacking in physicalism, but because something is lacking in us."

Zombies are the sharpest test. "Could a being share all your physical properties but have no conscious life?" Everybody's first thought, he says, is "Sure. Just duplicate the physical stuff and leave out the feelings." That concession is the trap: a physicalist who grants that zombies are metaphysically possible has already lost the argument. Papineau holds that physicalists must deny their possibility, "given that the mind is ontologically inseparable from the brain." If conscious states are physical states—radically identical—then "the 'two' cannot come apart," much as Marilyn Monroe cannot exist without Norma Jeane Baker. How could she exist without herself?[2]

Papineau also rejects the anti-physicalist claim that phenomenal concepts are revelatory, disclosing conscious states to be non-physical. "Physicalists respond that there is no reason to suppose that phenomenal concepts have the power to reveal such things … that experiences are non-physical." Why should introspection, he asks, "be guaranteed to tell us about all their necessary properties [of experience]?" (Papineau, 2020b.

Dissolving the Hard Problem

Papineau is blunt: "I never viewed the so-called 'hard problem' as any problem at all." The obvious answer, he says, is that brain processes feel like something for the subjects that have them. "What's so hard about that? … How would you expect them to feel? Like nothing? Why? That's how they feel when you have them."

The only reason many people believe there is a problem, he stresses, is that "they can't stop thinking in dualist terms" (Papineau, 2020b). The remedy is conviction rather than argument: "If only we could fully embrace physicalism, the feeling of an explanatory gap would disappear. If we could fully accept that pains are nociceptive-specific neuronal firing, then we would stop asking why 'they' go together—after all, nothing can possibly come apart from itself."

Applied to the problem of consciousness, the move is to "simply deny that any puzzle is raised by the fact that it feels painful to be a human with active nociceptive-neurons. Why shouldn't it feel like that? That's how it turns out. Why regard this as puzzling?" (Papineau, 2020a).

Vague Concepts and the Limits of Neuroscience

A commitment that distinguishes Papineau from most identity theorists emerges when he turns to what neuroscience can deliver. Against the conventional materialist expectation that research will eventually uncover the complete neurobiological basis of consciousness, he is skeptical. He does not expect that "there are definite facts about consciousness to which we lack epistemological access—that there is some material property that really constitutes being in pain, say, but which we can't find out about."

Rather, "our phenomenal concepts of conscious states are vague—nothing in the semantic constitution of phenomenal concepts determines precisely which of the candidate material properties they refer to" (Papineau, 2003).

Scientific research, he says, will identify "a range of material properties that correlate in human beings with pain, say, or colors, or indeed being conscious at all. However, this won't pinpoint the material essence of any such conscious state, for there will always be a plurality of such human material correlates for any conscious property … It is not as if conscious properties have true material essences, yet science is unable to discover them. Rather the whole idea of identifying such essences is a chimera, fostered by the impression that our phenomenal concepts of conscious states are more precise than they are" (Papineau, 2003).

This can look inconsistent with the flat assertion that conscious states are brain states, and the two claims are reconcilable only if the identity thesis is separated from a thesis about reference. Papineau holds that conscious states are neural states, and that phenomenal concepts refer to neural states, while denying that anything in the semantics of those concepts settles which of several nested or overlapping neural candidates is the referent. The identity is determinate as metaphysics and indeterminate as semantics: there is nothing more to being in pain than being in some such neural state, but no fact fixes exactly which one "pain" picks out. The consequence is a deflation of the usual research program—not that the essence of pain is hidden, but that there is no essence of the kind the program presupposes.[3]

Significance and Objections

Papineau's position is among the most fully worked-out versions of a posteriori or "type-B" physicalism, and his diagnosis of the dualist intuition has been widely adopted, often under other names, by physicalists pursuing what is now called the phenomenal concept strategy. It is contested on several fronts.

Chalmers argues that Papineau's commitment to identities that are metaphysically necessary yet not a priori derivable requires a notion of "strong metaphysical necessity" unlike any necessity found elsewhere in philosophy, and for which there is little independent reason. On this objection, appeals to reference by simulation and to the antipathetic fallacy restate rather than justify the commitment to explanatorily primitive identities. Chalmers further presses that declaring the mind-brain relation an identity does not discharge the obligation to supply a detailed theory of consciousness (Chalmers, 1996, 1999, 2006).

Sundström objects that the antipathetic fallacy over-predicts: it should generate a dualist intuition in cases where none arises. His example concerns an identity in which contemplating the left-hand side activates the relevant experience while contemplating the right-hand side does not, yet no intuition of distinctness appears. Papineau concedes the point is well taken while doubting it is conclusive, suggesting that reference may sometimes be filled out by imagining the experience on the right-hand side, and noting that his current view is that such activation is not essential to every deployment of a phenomenal concept (Sundström, 2008; Papineau, 2008, 2011). Kammerer develops refined counterexamples he argues cannot be answered in the same way, concluding that the intuition of distinctness cannot be explained as an antipathetic fallacy (Kammerer, 2018).

Goff presses the opposite objection to Papineau's account of phenomenal concepts, arguing that a posteriori physicalists misdescribe them, and that phenomenal concepts do reveal the natures of the properties they denote (Goff, 2011). Melnyk raises further difficulties for the diagnosis of the intuition of distinctness (Melnyk, 2003).

A separate line of criticism concerns the vagueness thesis rather than the identity thesis. If nothing fixes which of a plurality of neural correlates "pain" refers to, it is unclear what content remains in the claim that pain is a brain state, and unclear what a science of consciousness would be trying to establish. Contemporary type materialists who assert determinate psychoneural identities—that there is a fact about which neurobiological type each phenomenal type is, whether or not inquiry has found it—reject this half of Papineau's position while accepting his abductive method.

Finally, Papineau distinguishes his commitments carefully. Although his framing might seem to commit materialists to type identity while ignoring non-reductive physicalism, he has stated that this is not his intention (Papineau, 2011). Readers should treat the identity claims here as his considered view about conscious states specifically, not as a general endorsement of type-type reduction across the mental.

Footnotes

[1] Papineau distinguishes possibility from conceivability. "A posteriori physicalists have no choice but to allow that they [zombies] are at least conceivable," even if not possible (Papineau, 2020b).

[2] [RLK] But even if consciousness as an "output" or "effect" of the brain were wrongheaded, why are only certain sorts of neural activity identical with consciousness while others are not?

[3] Papineau's own reconciliation of the identity and vagueness theses is not stated in a single passage; the formulation here is a reconstruction from the material in Papineau (2003) and (2011).

References

Chalmers, D. J. (1996). The Conscious Mind: In Search of a Fundamental Theory. Oxford University Press.

Chalmers, D. J. (1999). Materialism and the metaphysics of modality. Philosophy and Phenomenological Research, 59(2), 473–496.

Chalmers, D. J. (2006). Phenomenal concepts and the explanatory gap. In T. Alter & S. Walter (Eds.), Phenomenal Concepts and Phenomenal Knowledge: New Essays on Consciousness and Physicalism. Oxford University Press.

Goff, P. (2011). A posteriori physicalists get our phenomenal concepts wrong. Australasian Journal of Philosophy, 89(2), 191–209.

Kammerer, F. (2018). Does the explanatory gap rest on a fallacy? Review of Philosophy and Psychology, 10(4), 649–667.

Levine, J. (1983). Materialism and qualia: The explanatory gap. Pacific Philosophical Quarterly, 64, 354–361.

Melnyk, A. (2003). Papineau on the intuition of distinctness. SWIF Forum on Thinking about Consciousness.

Papineau, D. (1993a). Physicalism, consciousness, and the antipathetic fallacy. Australasian Journal of Philosophy, 71, 169–183.

Papineau, D. (1993b). Philosophical Naturalism. Blackwell.

Papineau, D. (1995). The antipathetic fallacy and the boundaries of consciousness. In T. Metzinger (Ed.), Conscious Experience. Schöningh.

Papineau, D. (2002). Thinking About Consciousness. Oxford University Press.

Papineau, D. (2003). Could there be a science of consciousness?Phil. Issues, 13

Papineau, D. (2007). Kripke's proof is ad hominem not two-dimensional. Philosophical Perspectives, 21, 475–494.

Papineau, D. (2008). Phenomenal and perceptual concepts. In T. Alter & S. Walter (Eds.), Phenomenal Concepts and Phenomenal Knowledge. Oxford University Press.

Papineau, D. (2011). What exactly is the explanatory gap? Philosophia, 39(1), 5–19.

Papineau, D. (2020a). The problem of consciousness. Uriah Kriegel (Ed.), The Oxford Handbook of the Philosophy of Consciousness, Oxford University Press

Papineau, D. (2020b). We must shed our metaphysical assumptions. Instit. Art Ideas. https://iai.tv/articles/we-must-shed-our-metaphysical-assumptions-auid-1367

Papineau, D. (2021). The Metaphysics of Sensory Experience. Oxford University Press.

Sundström, P. (2008). Is the mystery an illusion? Papineau on the problem of consciousness. Synthese, 163(2), 133–143.