The Hard Problem of Physics (or: Why Sean Caroll is Wrong on Consciousness)

Physicst Sean Carroll has a new(ish) book out, The Big Picture, in which he basically lays down his answers to the Big Questions (the very thing this blog is interested in). I haven’t read it, but I’m a huge fan of Sean and from what he says about it in his promotional material I’m sure the book will be great.  I intend to buy it as soon as I have a little spare time to actually read it.Sean talks about how we already know the physics of everyday life, and much of the big picture stuff too, and what it means for morality (there are no objective moral truths; we have to make up our own morality) and so on. It really does look great.

But of course I’m not gonna write about any of that. I’m gonna focus on the negative, like the mean old curmudgeon that I am. Specifically, I want to say something about his view on consciousness, at least as it is presented in his teaser blog post “The Big Picture Part Five: Thinking“. Specifically, I want to raise the Hard Problem of Physics.

Sean very rightly mentions the Hard Problem of Consciousness. This is a term invented by philosopher David Chalmers to describe the difficulty of explaining how it is that certain configurations of matter (thinking brains) have the subjective feelings, or conscious experiences, that they do. We can, though physics and biology and so on, establish and explain how a system behaves and thus explain in detail (in theory) the information processing that goes on in the brain. But none of that tells us how the system feels. There is nothing in physics, nothing in science, that lets us jump from what something is (how a physical system is configured and how it changes dynamically) to how something feels (what  is it like to be this system, how does it feel like form the inside). This can be called the “is feels problem” (in analogy to the “is ought problem“). David Chalmers called it the Hard Problem.

In response to Chalmers, computer scientist Scott Aaronson recently coined the term “The Pretty Hard Problem”. The idea is roughly as follows: the Hard Problem implies that there are “psycho-physical laws”, namely that there are laws that would tell what a certain physical system (that’s the “-physical” part) would feel (that’s the “psycho-” part). The Hard Problem is all about understanding why these rules hold – why is it that such-and-such systems feel like that. The “Pretty Hard Problem”, in contrast, is the problem of establishing what these psycho=physical rules are. This is a very hard question, but it’s ultimately a scientific one – one proposes a set of rules, and one tests them empirically (in psychological & neural experiments) and judges them on the basis of their empirical success, simplicity, and so on.

Note the difference from the Hard Problem – it’s going to be very, very hard to establish the psycho-physical laws, but at least it’s a scientific question. I’t going to be impossible to establish why the fundamental psycho-physical laws are what they, however, including why they exist at all. That’s not a scientific question, so we don’t really have a handle on how to establish an answer to it.

There is another Hard Problem, the Hard Problem of Physics: why are the fundamental laws of physics what they are (including why there are such laws at all)? Again, it’s not a scientific question, so we don’t really have a handle on how to answer it. The best answer I’ve come across yet is Max Tegmark’s answer which is, roughly, that everything that is possible, exists; a position he terms the “Mathematical Universe” hypothesis. But even this feels unsatisfactory, as I’m left scratching my head as to why this should be the case (if indeed it is the case; it’s far from clear that it is).

Back to Sean Carroll. From the snippets he offered on his blog, Sean seems to maintain that the Hard Problem “will just gradually fade away as we understand more and more about how the brain actually does work”, and that ” the statement “I have a feeling…” is simply a way of talking about those signals appearing in your brain. There is one way of talking that speaks a vocabulary of neurons and synapses and so forth, and another way that speaks of people and their experiences.”

I disagree. Sort of. I think that understanding more and more about how the brain works will eventually lead us to solve the Pretty Hard Problem of consciousness, namely to experimentally establish a simple and successful “theory of consciousness”, that will be based on psycho-physical laws. These laws will appeal to aggregate entities such as attractors of the dynamic system or the irreducible causal-information within the system, and will associate these with consciousness. These aggregate quantities in this sense will be consciousness, just like “temperature” is the average kinetic energy of matter. And this will allow us to provide a detailed mechanical explanation for mental causation. We could, for example, show that “anger caused him to lash out” in that we could very-specifically identify the aggregate that feels-like anger in the person’s brain and show how its activation causally led to the person lashing out. (In theory. This is a hopeful, far-future scenario.)

Nevertheless, even this future successful theory will not solve the Hard Problem of Consciousness. It will not reveal why these psycho-physical laws hold, or why any such laws hold in the first place. It will not solve the central mystery of consciousness – why and how is it that this piece of matter, this mushy agglomerate of fat and neural tissue, feels. It won’t explain to us, as Sean puts it, “how can collections of such cells or particles ever be said to have an experience of “what it is like” to feel something?”. All it will do, is describe how consciousness works; it won’t provide an ultimate explanation for why it works this way.

Now, this is supposed to be a big deal I guess. I’m not too worried about it. Just like we will never be able to solve the Hard Problem of Physics, we won’t be able to solve the Hard Problem of Consciousness. They are too hard. We can, through science, describe the fundamental laws of nature, including both the laws of physics and the psycho-physical laws. But we cannot, scientifically, establish why these laws hold. And I doubt very much we can establish why they hold philosophically (philosophers have been trying for millennia, and we aren’t any smarter or more knowledgeable about this then they were). The best I can hope for is that the fundamental laws would turn out to be so simple, that we’d be led to think that they kinda make sense – like Max Tegmark’s Mathematical Universe hypothesis.


One thought on “The Hard Problem of Physics (or: Why Sean Caroll is Wrong on Consciousness)

  1. There were once upon a (ancient) time a group of philosophers debating about whether there is (actual) movement in the universe or not. These were from various schools. Then sudenly one cynic philosopher stood up and walked away from the group, and the debate was over.

    At another time in some exotic place, there was a fisherman, standing by a lake, fishing. He was about middle age, he was also a farmer. He had taken out his tools of fishing, laid them out in a fashion suitable to do his work and started fishing. After a while another man came, sat some distance from the fisherman and was watching. After a while he asked the fisherman. What do you think about the universe, why is it there and how it came about? The fisherman replied: i’m not interested.

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