Papineau’s Mind-Brain Identity

Philosopher David Papineau argues for neurobiological physicalism with his theory of unabashed, robust, fundamental mind-brain identity. It is an important argument, with implications for all materialist theories (Papineau, 2020b).

In constructing the argument, one of Papineau's 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 kind of things, biological, meteorological, chemical, electrical, and so on, all existing alongside each other, and all interacting causally in various ways” (Papineau, 2020b).

The Explanatory Gap and Dualist Intuitions

One Papineau premise is that while we feel “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,” 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 notes that we remain puzzled about why brain states give rise to mental states “in a way that we don't feel puzzled about why NaCl gives rise to salt, or electrical discharges to lightning.” He attributes our puzzlement—the “explanatory gap” of consciousness—to the psycho-social fact that “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).

Given this, Papineau says 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 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.”

Abductive Identity and the Zombie Challenge

In exploring the basis of identity claims, Papineau states that “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, in Papineau's view, “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.”

“If only we could fully embrace physicalism,” Papineau suggests, “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.”

To Papineau, this kind of robust physicalism can dissolve “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).

An insight is the connotation of verbs used to describe the relation between mind and brain. Brain processes are said to “generate,” or “yield,” or “cause,” or “give rise to” conscious states. But this phraseology, Papineau says, undermines physicalism from the start—even when used by physicalists. 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).

(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?)

To sustain his argument, Papineau must deal with zombies. Are zombies possible? “Could a being share all your physical properties but have no conscious life?” Everybody's first thought is, he says, “Sure. Just duplicate the physical stuff and leave out the feelings.”

That's the anti-physicalist “trap”: the physicalist has already lost. Papineau rightly states that physicalists must deny that zombies are possible, “given that the mind is ontologically inseparable from the brain.” If conscious states are physical states—radically identical—then, he says, “the ‘two’ cannot come apart,” much like Marilyn Monroe cannot exist without Norma Jean Baker. How could she exist without herself? That makes no sense, he says.^[1]

Papineau rejects the anti-physicalist argument that phenomenal concepts are revelatory, in that they reveal conscious states not to be 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 rhetorically, “be guaranteed to tell us about all their necessary properties [of experience]?” (Papineau, 2020b).

Dissolving the Hard Problem and Limits of Neuroscience

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 that many people believe there is a problem, Papineau stresses, is that “they can't stop thinking in dualist terms” (Papineau, 2020b).

As for the conventional materialist claim that ultimately neuroscience will uncover the complete neurobiological basis of consciousness, Papineau 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, he argues, “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).

Footnote

[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).