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.
I've been leaning a bit more towards deflationism lately. Certainly some of the things we think of as ineffable knowledge are just really complicated - I have emotions and instincts and memories of colors that I could not put into words no matter how hard I tried. If that's not ineffable, what is?
But we have this intuition that there is a further fact about the blueness of blue, some part of your color experience that consists of the mysterious blueness of blue independent of any instincts or associations or memories. But I think that this thing is purely the judgment that something is blue. It's what a movie camera feels like from inside - an extremely simple core of experience. And therefore this part is in fact effable - "that thing looks blue" is a sufficient effing.
Of course, a representation doesn't seem like a representation from inside. From the perspective of a cognitive algorithm that uses this representation, the representation seems like direct access to the world, and there's no evolutionary pressure to learn otherwise.
This identification of the mysterious blueness of blue with the simple fact that our representation of the world marks some patch of the sensorium as blue explains many weird properties of the mysterious blueness. It's difficult to break down into other mental pieces (because it's already simple). It's intimately related to first-person experience. Someone who has never seen a blue thing in some sense "doesn't know what it feels like to see blue," no matter their third-hand knowledge, but in another sense there's almost nothing to "know" about seeing blue, it's more in the class of something that happens to you. There's nothing else quite like the blueness of blue - because it's nearly a primitive feature of our senses.
Sorry for going off on my own little tangent, I was thinking about this on the bus earlier today.
No, it's what we usually call a percept. "Physical model" usually refers to something outside the head, like a set of equations on a blackboard, or a computer model.
You have compressed together two different claims -- the claim that Alice needs detailed and complete information about Bob's brain, and the claim that she needs to hold it in her own head.
The original Knowledge (Mary's Room) argument starts form the assumption that 3rd-person (stored externally to the brain) knowledge is sufficient for most things in science. The idea that there is a special class of things which require 1st-person instantiation introduces a dualism. The idea that all science is subjective and 1st-person is just wrong.
Physicalists sometimes respond to Mary's Room by saying that one can not expect Mary actually to actually instantiate Red herself just by looking at a brain scan. It seems obvious to then that a physical description of brain state won't convey what that state is like, because it doesn't put you into that state. As an argument for physicalism, the strategy is to accept that qualia exist, but argue that they present no unexpected behaviour, or other difficulties for physicalism.
That is correct as stated but somewhat misleading: the problem is why is it necessary, in the case of experience, and only in the case of experience to instantiate it in order to fully understand it. Obviously, it is true a that a descirption of a brain state won't put you into that brain state. But that doesn't show that there is nothing unusual about qualia. The problem is that there in no other case does it seem necessary to instantiate a brain state in order to undertstand something.
If another version of Mary were shut up to learn everything about, say, nuclear fusion, the question "would she actually know about nuclear fusion" could only be answered "yes, of course....didn't you just say she knows everything"? The idea that she would have to instantiate a fusion reaction within her own body in order to understand fusion is quite counterintuitive. Similarly, a description of photosynthesis will make you photosynthesise, and would not be needed for a complete understanding of photosynthesis.
There seem to be some edge cases.: for instance, would an alternative Mary know everything about heart attacks without having one herself? Well, she would know everything except what a heart attack feels like, and what it feels like is a quale. the edge cases, like that one, are cases are just cases where an element of knowledge-by-acquaintance is needed for complete knowledge. Even other mental phenomena don't suffer from this peculiarity. Thoughts and memories are straightforwardly expressible in words, so long as they don't involve qualia.
So: is the response "well, she has never actually instantiated colour vision in her own brain" one that lays to rest and the challenge posed by the Knowledge argument, leaving physicalism undisturbed? The fact that these physicalists feel it would be in some way necessary to instantiate colour, but not other things, like photosynthesis or fusion, means they subscribe to the idea that there is something epistemically unique about qualia/experience, even if they resist the idea that qualia are metaphysically unique.
Is the assumption of epistemological uniqueness to be expected given physicalism? Some argue that no matter how much you know about something "from the outside", you quite naturally wouldn't be expected to understand it from the inside. That's a common intuition, as shown by the frequency of rhetoric along the lines of "you wouldn't know, you weren't there". We will go on to argue that Being There is not strictly compatible with physicalism.
Instantiation/representation/having a model, in my view, is not binary and is needed for any understanding. You seem to say that I don't think 'understanding' requires instantiation. My example with the bowl is meant to say that you do require a non-zero degree of instantiation - although I would call it modelling instead because instantiation makes me think of a temporal model, but bowls can be represented as static without losing their defining features. In short, no model=no understanding is my claim. This is an attempt to make the word knowledge more precise because it can mean many things.
I then go on to describe why you need a more high fidelity model to represent the defining features of someone's brain state evolving over some time period. The human brain is obviously incapable of that. Although an exact subatomic model of a bowl contains a lot of information too, you can abstract much more of it away without losing anything essential.
I'd also like to correct that I make no claims that science, or anything, is subjective. Conversely, I'm claiming that subjectivity is not a fundamental concept and we can taboo it in discussions like these.
The crucial question is whether the model needs to be inside-the-head in some or all cases.
I don't see the usefulness of tabooing subjectivity when it is the whole point.
Where else would the model be if not inside the head? Or are you saying one can 'understand' physical objects without any hint of a model?
To quote myself:
Gotcha, I'm referring to a representation encoded in neuron activity, which is the physical process.
On the other hand, would someone who has a heart attack know as much as Mary about what's going on?
Would Mary learn any new information over the course of a heart attack?
It might be new information, it might be the same information presented in a different way. But the latter is still not something implied by physics...physics doesn't suggest that different modes of presentation, or irreducibly subjective perspectives should exist.
The new information would be which nerves correspond to the heart (which is more than most need to know about heart attacks), and how they respond to that situation. I'm not positing irreducibility, I just haven't seen research conclusively wrapping up how to measure pain objectively yet.