This is an essay I wrote a few years back that some people have found helpful. The writing needs some polishing but I'm posting as-is. Thanks to Ruairi Donelly for originally encouraging me to write it and now also for encouraging me to post it here. Summary is at the end.
Experts strongly disagree on consciousness, even among smart philosophers and people I personally trust to think about it in rational ways. Having considered many arguments and thought of ways to change my perspective on consciousness, my impression is that much of the disagreement stems from strong, differing intuitions. Physicalists feel that what we call subjective experience is simply identical with the physical processes in our brains. Dualists see a fundamental difference between the two and generally can’t imagine them being the same. As such, dualism has much more intuitive appeal to many people, myself included, but I think that it’s mistaken.
I would like to bring a new argument to the debate which could resolve some confusions. It addresses the knowledge-argument, which says that consciousness is private. Many existing arguments already address the knowledge-argument. I’m just writing out the argument in this essay because it has helped some people get more intuition about why the subjectivity of consciousness is an appealing yet ultimately wrongheaded intuition that defies physicalism.
I won’t explain the full reasoning for the view that consciousness is purely a physical (or ‘analytically functional’) process, this is just meant to be one piece in the puzzle. In short, reductionists will agree that something akin to physicalism should be accepted if it’s even conceivably true. One important reason is that non-reductive views such as dualism violate Occam’s razor in multiple ways.
The knowledge problem
A common question in debates about consciousness is whether Alice could fully understand what Bob subjectively experiences if she had perfect knowledge about the physical processes in Bob's brain. This is the topic of Frank Jackson's famous thought experiment about Mary, the colour scientist and Thomas Nagel’s ‘What is it like to be a bat?'. In a similar way, dualist intuitions are often defended with the argument that consciousness is private, subjective or ineffable. This distinguishes consciousness from physical processes, which can be observed by anyone. Consequently, there must be more than physical knowledge and this other knowledge must be about something that’s not physical. This is known as the knowledge argument.
The spirit of these arguments could be summarised as follows: There is a third-person perspective and a first-person perspective to the processes in Bob’s brain. The first-person perspective is what we call Bob’s subjective experience. First-person perspectives aren’t a fundamental concept in physics and yet it seems that having access to one determines what can be known. Let’s call the existence of the first-person perspective subjectivity.
Even people who don’t agree with Jackson’s or Nagel’s thought experiments often find that subjectivity is at odds with consciousness being physical. Brian Tomasik shows how the problem relates to first-person and third-person perspectives:
"When we imagine deriving the behavior of a car from its atomic configuration, we can think about all parts of the system in third-person terms. We adopt a physical stance toward the atoms, and the metal/plastic pieces, and the whole joint system. Phenomenal experience is different because this requires shifting from third-person to first-person, which is a switch that no other scientific reduction needs."
He makes the point I’ll make below by referring to ‘acquaintance knowledge’:
“Phenomenal consciousness is analytically functional [here: physical], but it's also sort of epistemically inaccessible in an acquaintance rather than propositional sense. The acquaintance view makes us feel better about explaining qualia than crude type-A caricatures while not allowing for the ideal conceivability of zombies as would be the case for type B.”
However, acquaintance knowledge is just an intuition pump, and Brian acknowledges that it’s not easy to verify if it’s just “linguistic trickery”. The idea of acquaintance knowledge was first stated by philosopher Earl Conee (1994) as an objection to the knowledge argument.
A new argument
I propose an argument that I find more intuitively convincing. Let’s examine what we mean by the words ‘knowledge’ and ’third-person perspective'. If you look at, say, a bowl, you gain knowledge of its physical properties such as its shape and colour from a third-person perspective. First, light reflects off the bowl which reaches your eyes and gets transformed into electrical signals. The brain then recognizes shapes etc. in these signals. The crucial point is that it then forms an abstraction, i.e. a model of the bowl. This model in your brain is what we typically call the physical knowledge about the bowl. The abstraction itself is physically stored like a hard drive would store an image file. When you remember what the bowl looks like, the abstraction is broadcast into your brain so that it is physically part of your consciousness (on a physicalist account). Since you can form a roughly accurate model of everything about the bowl we find relevant, we say that everything about the bowl is accessible from a third-person perspective.
Now let’s compare this to the physical knowledge A could gain about B's brain processes and the associated ‘subjective' experience. If A were to look at an MRI scan of B’s brain, A would form an abstraction of B’s brain that is simply an image. This abstraction would, of course, not do justice to the complexity of the processes in B’s brain. It could possibly be stored on a floppy disk. In order to know all the physical knowledge about B’s brain processes, A would have to form an accurate abstraction. This much harder for a brain than for a bowl, because brain processes have many more details that we care about.
If A were to actually form an abstraction of Bob’s brain that captures the aspects that matter, Alice would have to run nearly every aspect of it in her own brain. The relevant aspects include e.g. the content of Alice’s working memory, i.e. the neural activations that are necessary to compute the concepts present in the working memory, with all their relevant properties, as well as the relationships between them. This would amount to something close to simulating Bob’s brain inside Alice’s brain. If Alice had suitably advanced brain that could actually do this, Alice may herself experience what Bob experiences. Therefore, the knowledge argument fails: By perfect physical knowledge of a brain we mean forming an accurate abstraction (perhaps even a simulation) of it in our own brain. This entails the subjective experience.
This is not the first objection to the knowledge argument and the point is not to add another one. Rather, I’d like to resolve the confusion around first-person and third-person perspectives. These concepts don’t have a place in physics (to my knowledge) but they still appear to determine what we can know. What I’ve tried to show is that having a third-person view of something reduces to forming an abstraction of that thing in our brain. The third-person perspective is simply a concept we’ve invented because we don’t usually think through the whole process of forming an abstraction.
This leaves us with only the first-person perspective. But since there are no perspectives left to contrast it with, we can best do away with the idea of perspectives altogether (at least when it comes to the ontology of mental processes). I think that without these concepts, physicalism can become more intuitive. ‘Somebody being an algorithm viewed from the inside’ simply reduces to the existence of an algorithm at some point in space and time. If I say ‘I’m experiencing the smell of apple right now’ I’m simply saying that there is an apple-pie-smell algorithm going on here. (Why am ‘I’ this particular kind of algorithm and not some other one? That question, while puzzling, is not only outside the scope of this essay, but also probably outside the field of philosophy of mind. It seems more related to anthropics, the study of indexical information).
Going back to Earl Conee’s and Brian Tomasik’s concept of acquaintance knowledge we could now say that this is the only kind of knowledge, just like first-person is the only perspective left. Propositional knowledge simply means having, in some part of our brain where it is not used, the data needed to form an abstraction of something. We can then access this knowledge and become acquainted with it by putting it into our awareness. Once again, I think it’s best to do away with the different kinds of knowledge in discussions about consciousness because they’re just how we conceptualise of physical processes things going on in our brain.
Changing intuitions about consciousness
This was one of the things that are most counterintuitive about physicalism to me: There appears to be a phenomenal experience, which can’t be seen from the outside. Since the view from the outside is just a concept we invented, this is not a reason for concern. One remaining challenge for our intuitions is to identify two things which intuitively feel very different from one another: The physical processes in our brain and what we call our subjective experience. We conceptualise these things in very different ways which makes it hard to see them as identical. (For example, we think of consciousness as unified and physical processes as individual atoms moving around). I hope I’ve removed one obstacle to doing so. I don’t think that this piece would have intuitively and intellectually convinced me all by itself a while ago, when my intuitions were still strongly at odds with physicalism. Changing them can take a long time, can’t be done in one essay and involves overriding very deep-rooted intuitions. I think this is why very smart and rational people often cannot accurately model each other. Having been on both sides, I feel I have a better model of both now.
It feels a bit cheap to say that the rest is just about changing intuitions, without actually giving any more arguments, but I can’t avoid it. I highly recommend several of Brian’s essays which can further help change intuitions, but the most important aspect is an open mind towards a view that can at times be mind-bogglingly counterintuitive.
In summary, I have argued something quite simple: The third-person perspective and the idea of knowledge are just ways of saying that we form an abstraction of something in our brain which we may then be conscious of. If we formed a sufficiently detailed abstraction of another person’s brain, the processes constituting their subjective experience would also happen inside us. Therefore, the knowledge argument fails. But more importantly, perspectives are not a fundamental thing, which makes it easier to accept that subjective experience is simply the existence of a particular neural algorithm (rather than an inaccessible first-person perspective, which is not a thing in physics).
Objection: When A simulates B’s brain in her own brain, it’s not A, but B that has the experience.
This misses the point: The point is that there is no third-person perspective, just forming abstractions of things, so we can’t expect Alice to get a third-person peek into Bob’s experience. Besides, persons are not fundamental (or even a thing) on the physicalist view we're trying to critique here. Whether it’s Alice or Bob having the experience is therefore just semantics.
What about the zombie argument?
By my understanding, David Chalmer's well-known zombie argument only argues against type-B physicalism (or type-B materialism as Chalmers calls it), the view that there is an epistemic gap between physics and subjective experience, but this gap doesn’t mean that there is stuff other than physics. I’m defending a view called type-A physicalism, which states there is no epistemic gap and that consciousness is simply what physics does in our brain. My argument here is supposed to provide one idea needed to close the perceived epistemic gap. I’m happy to provide an explanation why type-A physicalism isn’t affected by the zombie argument if it’s unclear.