A year ago we met an alien species (Part I) that lacked subjective conscious states but were virtuoso scientists. They developed a detailed understanding of cat brains at every level of organization, but still did not realize that cats were conscious. This was parlayed into an argument for dualism (Part II). Namely, if full knowledge of a brain doesn’t reveal subjectivity, and this is a logically necessary limitation of any purely neural approach, then this is an inductive catastrophe for the materialist. In this post I explore (and ultimately reject) the idea that phenomenal concepts provide a way out for the materialist. I suggest that a better escape for the materialist is to reject the view that knowledge of subjectivity is necessarily sealed off from neural theories.
In Part I, I introduced an alien species that lacked conscious experiences (and concepts about such experiences), but acquired detailed scientific knowledge of the cat brain at every level of organization. This included knowledge of complex neural states that the aliens called ‘smonscious states’ which isomorphically and intuitively mapped onto (what we would call) the cats’ conscious subjective experiences.
However, as discussed in Part II, the aliens never came to understand that the cats have subjective experiences, as such. This is not, by itself, a problem. It is justifiably a truism that conceptual differences do not imply ontological differences. When Mendel talked about genes in pea plants, he wasn’t intending to talk about complex stretches of DNA. Similarly, perhaps there is one underlying neural reality that can be accessed and conceived in two ways. Experiences can be described in neuroscientific terms that are available to outsiders that study brains, and in phenomenal terms available to those insiders whose brains instantiate the relevant properties. While there is admittedly a dichotomy of concepts, there is no dichotomy of properties or substances.
The dualists are familiar with such considerations, and their argument doesn’t merely depend on a semantic difference, but on the semantic poverty of neuroscience. That is, it seems that no amount of analysis, conjunction, or <insert your favorite semantic construction method here> applied to concepts about brain states will yield a concept about subjective experience as such. We’ll call this the semantic poverty thesis . If the aliens are restricted to theorizing based only on their neuronal theory (they are), they could never in principle come to understand that cats have experiences.
There is no semantic poverty thesis for any of the standard examples of co-referring concepts from the natural sciences. For instance, it seems easy to imagine how our scientifically astute aliens could bridge the relevant conceptual domains between molecular biology and Mendelian genetics. If restricting oneself to neuronal theories permanently seals you off from knowing that subjects are conscious, then we seem to have an inductive catastrophe for the materialist, regardless of any plausibility-straining logical possibilities.
Phenomenal concepts to the rescue?
Many naturalists simply accept the semantic poverty thesis, and argue that materialism is still the best game in town. In particular, it is popular to attempt to explain semantic poverty using the phenomenal concepts strategy (PCS). This involves the hypothesis that there exists a special set of concepts that we use to directly refer to our own experiences, concepts that can initially only be acquired by those who instantiate the relevant subjective experiences. Folks have been doing phenomenology, directly describing their perceptual experiences, for centuries, independently of any scientific understanding of said experiences. We can say things like ‘That pain in my tooth has returned’ independently of any thoughts about the basis of the pain, without a jot of abstruse metaphysical knowledge.
Since our phenomenal conception of experience can be deployed without staking any claim as to the basis of such experiences, it is not surprising that people can conceive of experiences occurring independently of brains. Carruthers and Veillet (2007) write:
[W]e possess a special set of concepts for referring to our own experiences. What is said to be distinctive of such concepts is that they are conceptually isolated from any other concepts that we possess, lacking any a priori connections with non-phenomenal concepts of any type (and in particular, lacking such connections with any physical, functional, or intentional concepts). Given that phenomenal concepts are isolated, the physicalist argues, then it won’t be the least bit surprising that we can conceive of zombies and inverts, or that there should be gaps in explanation. This is because no matter how much information one is given in physical, functional, or intentional terms, it will always be possible for us intelligibly to think, “Still, all that might be true, and still this [phenomenal feel] might be absent or different.” There is no need, then, to jump to the anti-physicalist conclusion.
That is, if PCS is correct, then we should expect that people can (incorrectly) think that there could exist ghosts (agents with mental states that float about independently of brains), or philosophical zombies (physical duplicates that lack the same conscious experiences as us). But we should resist the temptation to slide into ontological dualism based on such merely conceptual exercises.
While interesting, the PCS doesn’t directly deflect the dualist’s concerns. For one, it explicitly affirms the dualist’s premise that the aliens will never know that the cats are conscious. But this is precisely the problem. If we are meant to take the alien’s theory as a literally true and complete account of the properties of the cat’s brain (we are), and consciousness is a property literally instantiated by the cats (it is), then the aliens’ neural theory is simply incomplete. A complete inventory of reality should explicitly mention conscious experiences, and it should be seen as a scandal for materialism that if you limit yourself to neuronal theories, you will never acquire the knowledge that subjects are conscious.
Using the PCS, the materialist squirms around shifting the discussion from consciousness to concepts about consciousness. In contrast, the dualist is on much stronger footing when it comes to explaining phenomenal experiences. She can unflinchingly focus directly on the system instantiating the relevant properties, and will not wind up in the embarrassing situation in which someone understands their dualistic theory but does not know that cats have experiences.
Note just how low the bar is set for the materialist. We aren’t asking for the aliens to know the subjective character of red, but to realize that there is some experience there, period. It seems reasonable to expect a complete theory would leave the aliens in a position analogous to Mary before she leaves her black and white jail. That is, she knows she lacks color experiences (i.e., her brain has yet to instantiate the relevant color-seeing properties), and she knows she lacks the typical cognitive reactions to having that experience (e.g., she will not recognize red when she sees it the first time). We don’t expect her (or the aliens) to acquire the experiences she is studying. This would actually go against the thesis under question, that experiences are brain states of a certain type. We would not expect our aliens to experience red any more than we expect to photosynthesize upon acquiring expertise on the topic of photosynthesis. Materialists are committed to the view that experiences are brain states, not that studying consciousness magically induces such brain states.
So the bar is set pretty low, and while logically possible as a materialist response, the phenomenal concept strategy amounts to blithely running underneath the bar .
A better option for the materialist, who wants to avoid going down this road, is to attack the semantic poverty thesis. After all, nobody has given a particularly strong argument for the claim. It is typically either treated as axiomatic, or perhaps some halfhearted justification is presented. For instance, Chalmers (1995) writes:
But the structure and dynamics of physical processes yield only more structure and dynamics, so structures and functions are all we can expect these processes to explain. The facts about experience cannot be an automatic consequence of any physical account, as it is conceptually coherent that any given process could exist without experience.
It seems a mistake to allow substantive debates to be swayed based on inconclusive declarations about how two extremely complex domains relate to one another. In the next (and last) post [Part IV], I will develop a case against semantic poverty, arguing that the aliens could close the gap between brains and experiences. This will allow materialists to jump over the bar that was set above.
Notes If true, the semantic poverty thesis implies there is an explanatory gap, a ‘Hard Problem’ of explaining consciousness: if neuroscience is too conceptually impoverished to say you are having an experience, there is no way it can explain said experience (at least in the sense of ‘explains’ that Chalmers uses to underwrite the Hard Problem). I am presently leaving out the possibility that the aliens could learn about phenomenal concepts if they talked to, or studied, humans, as it seems to be a cheat.  I am actually more sympathetic to the PCS than I let on here, but to save space I am moving on rather quickly to what seems a better response.
Carruthers, P, and Veillet, B (2007). The Phenomenal Concept Strategy. Journal of Consciousness Studies 14: 212-236.
Chalmers, D (1995) Facing up to the problem of consciousness. Journal of Consciousness Studies 2: 200-219.