So you do think there is a difference between physicalism and computationalism even if the Church-Turing-Deutsch principle is true? And this difference is something to do with a special status held by the real world vs. simulations of the real world? I’m trying to understand what these competing theories are but there seems to be a communication problem that means you are failing to convey them to me.
And this difference is something to do with a special status held by the real world vs. simulations of the real world?
That’s what it means to say that physicalism is substrate-dependent. There is a (simple) psycho-physical law which states that subjective experience is implemented on a specific substrate.
It just so happens that evolution has invented some analog supercomputers called “brains” and optimized them for computational efficiency. At some point, it hit on a “trick” for running quantum computations with larger and larger state spaces, and started implementing useful algorithms such as reinforcement learning, aversive learning, perception, cognition etc. on this substrate. As it turns out, the most efficient physical implementations of such quantum algorithms have subjective experience as a side effect, or perhaps as a crucial building block. So subjective awareness got selected for and persisted in the population to this day.
It seems a fairly simple story to me. What’s wrong with it?
That’s what it means to say that physicalism is substrate-dependent. There is a (simple) psycho-physical law which states that subjective experience is implemented on a specific substrate.
So is one of the properties of that specific substrate (the physical world) that it cannot be simulated by a Turing machine? I don’t know why you can’t just give a yes/no answer to that question. I’ve stated it explicitly enough times now that you just come across as deliberately obtuse by not answering it.
I think I’ve been fairly clear that I don’t deny the possibility that consciousness depends on non-computable physics. I don’t think it is the most likely explanation but it doesn’t seem to be clearly ruled out given our current understanding of the universe. Your story might be something close to the truth if the Church-Turing-Deutsch principle is false. It appears to me to be incoherent if it is true however.
I think the Church-Turing-Deutsch principle is probably true but I don’t think we can rule out the possibility that it is false. If it is true then it seems a simulation of a human running on a conventional computer would be just as conscious as a real human. If it is false then it is not possible to simulate a human being on a conventional computer and it therefore doesn’t make sense to say that such a simulation cannot be conscious because a simulation cannot be created. What if anything do you disagree with from those claims?
Your story might be something close to the truth if the Church-Turing-Deutsch principle is false. It appears to me to be incoherent if it is true however.
Because it implies the possibility of zombies, or for some other reason?
Because it implies the possibility of zombies, or for some other reason?
Basically, yes. Slightly more explicitly, it appears to say that two contradictory things are true: that a Turing machine can simulate every physical process but that there are properties arising from physical processes running directly on their ‘native’ hardware that do not arise when those same processes are simulated. That suggests either that the simulation is actually incomplete (it is missing inputs or algorithms that account for the difference) or that there is some kind of dualism going on: a mysterious and unidentifiable ‘something’ that accounts for consciousness existing in a human brain but not in a perfect simulation of a human brain.
If the missing something is not part of physics then we’re really back to dualism and not physicalism at all. It seems like an attempt to sneak dualism back in without admitting to being a dualist in polite company.
there are properties arising from physical processes running directly on their ‘native’ hardware that do not arise when those same processes are simulated.
Is subjective experience a “property”? By assumption, all the features of subjective experience have physical correlates which are preserved by the simulation. It’s just that the ‘native’ process fits a “format” that allows it to actually be experienced, whereas the simulated version does not. It seems weird to call this a dualist theory when the only commonality is an insistence on taking the problem of subjective experience seriously.
Well, I don’t think it really matters what you call it but I assume we agree that it is a something. Do you believe that it is in principle possible to differentiate between an entity that has that something and an entity that does not?
By assumption, all the features of subjective experience have physical correlates which are preserved by the simulation.
This sounds like your answer to my previous question is ‘no’. So is your position that it is not possible in principle to distinguish between a simulation of a human brain and a ‘real’ human brain but that the latter differs in that it possesses a ‘something’ that is not a function of the laws of physics and is inaccessible to any form of investigation other than introspection by the inhabitant of that brain but that is nonetheless in some sense a meaningful distinction? That sounds a lot like dualism to me.
Do you believe that it is in principle possible to differentiate between an entity that has that something and an entity that does not?
Perhaps not. ‘That something’ may be simply a model which translates the aforementioned physical properties into perceptual terms which are more familiar to us. But this begs the question of why we would be familiar with perception in the first place; “we have subjective experience, and by extension so does anything which is implemented in the same substrate as us” is a good way to escape that dilemma.
the latter differs in that it possesses a ‘something’ that is not a function of the laws of physics and is inaccessible to any form of investigation other than introspection by the inhabitant of that brain
The whole point of physicalism is that subjective experience is a function of the laws of physics, and in fact a fairly low-level function. If you want to avoid any hint of dualism, just remove the “inhabitant” (a misnomer) and the “psycho-physical bridging laws” from the model and enjoy your purely physicalistic theory. Just don’t expect it to do a good job of talking about phenomenology or qualia: physicalist theories are just weird like that.
As the saying goes, those who do not know dualism are doomed to reinvent it, poorly. Beware this tendency.
Are you saying that there is some extra law (on top of the physical laws that explain how our brains implement our cognitive algorithms) that maps our cognitive algorithms, or a certain way of implementing them, to consiousness? So that, in principal, the universe could have not had that law, and we would do all the same things, run all the same cognitive algorithms, but not be consious? Do you believe that p-zombies are conceptially possible?
The psycho-physical law is not really an extra law “on top of the laws of physics”, so much as a correspondence between quantum state spaces and subjective experiences—ideally, the correspondence would be as simple as possible.
You could build a version of the universe which was not endowed with any psycho-physical laws, but it’s not something anyone would ever experience; it would be one formal system plucked out seemingly at random from the set of computational structures. It is as logically possible as anything else, but whether it makes sense to regard such a bizarre thing as “conceptually possible” is another matter.
You could build a version of the universe which was not endowed with any psycho-physical laws, but it’s not something anyone would ever experience;
But would this universe look the same as our universe to an outside observer who cannot directly observe subjective experience, but only the physical states that subjective experience supposedly correspond to?
We’re assuming that physicalism is true, so yes it would look the same. The inhabitants would be p-zombies, but all physical correlates of subjective experience would exist.
So, since in this alternate universe without subjective experience, people have the same discussions about subjective experience as their analogs in this universe, the subjective experience is not the cause of these discussions. So what explains the fact the this physical stuff people are made out of, which only obeys physical laws and can’t be influenced by subjective experience, discusses subjective experience? Where did that improbability come from?
So what explains the fact the this physical stuff people are made out of, which only obeys physical laws and can’t be influenced by subjective experience, discusses subjective experience?
First of all, physical stuff can be influenced by the physical correlates of subjective experience. Since the zombie universe was obtained by removing subjective experience from an universe where it originally existed, it’s not surprising that these physical correlates would show some of the same properties.
The properties which subjective experience and its physical correlates have in this universe could be well explained by a combination of (1) anthropic principles (2) the psycho-physical bridging law (3) the properties of our perceptions and other qualia. Moreover, the fact that we’re having this discussion screens out the possibility that people might have no inclination at all to talk about subjective experience.
First of all, physical stuff can be influenced by the physical correlates of subjective experience.
If the physical properties of the physical correlates of subjective experience are sufficient to explain why we talk about subject experience even without a bridging law, then why are they not enough to also explain the subjective experiences without a bridging law?
Subjective experience is self-evident enough to need no explanation. What needs to be explained is how its content as perceived by us (i.e. qualia, beliefs, thoughts etc.) relates to formally modeled physics: hence, the bridging law maps between the conceptual description and the complex quantum system which is physically implemented in the brain.
Subjective experience is self-evident enough to need no explanation.
No, subjective experience is self-evident enough that we do not need to argue about whether it exists, we can easily agree that it does. (Though, you seem to believe that in the zombie world, we would incorrectly come to the same agreement.) But agreeing that something exists is not the same as understanding how or why it exists. This part is not self-evident and we disagree about it. You seem to believe that the explanation requires macroscopic quantum superpositions and some bringing law that somewhat arbitrarily maps these quantum superpositions onto subjective experiences. I believe that if we had sufficient computing power and knew fully the arrangement of neurons in a brain, we could explain it using only classical approximations of physics.
But agreeing that something exists is not the same as understanding how or why it exists.
We don’t understand why, but then again we don’t know why anything exists. In practice, something as basic as subjective experience is always taken as a given. As for how, our inner phenomenology reveals far more about subjective experience than physics ever could.
Nevertheless, we do also want to know how the self might relate to our physical models; and contrary to what might be expected, macroscopic quantum superposition is actually the parsimonious hypothesis here for a wide variety of reasons.
Unless QM as we know it is badly wrong, it just doesn’t fit our models of physical reality that anything resembling “the self” would be instantiated in a hugely complicated classical system (a brain with an arrangement of brain regions and billions of neurons? Talk about an arbitrary bridging law!) as opposed to a comparatively simple quantum state.
Moreover, it is eminently plausible that evolution should have found some ways of exploiting quantum computation in the brain during its millions-of-years-long development. The current state of neuroscience is admittedly unsatisfactory, but this shouldn’t cause us to shed too much confidence.
We don’t understand why, but then again we don’t know why anything exists.
I am talking about why subjective experience exists given that the physical universe exists. Are you being deliberately obtuse?
Unless QM as we know it is badly wrong, it just doesn’t fit our models of physical reality that anything resembling “the self” would be instantiated in a hugely complicated classical system (a brain with an arrangement of brain areas and billions of neurons? Talk about an arbitrary bridging law!) as opposed to a comparatively simple quantum state.
You are failing to address my actual position, which is that there is no arbitrary bridging law, but a mapping from the mathematical structure of physical systems to subjective experience, because that mathematical structure is the subjective experience, and it mathematically has to be that way. The explanation of why and how I am talking about is an understanding of that mathematical structure, and how physical systems can have that structure.
If you believe that we evolved systems for maintaining stable macroscopic quantum superposition without decoherence, and that we have not noticed this when we study the brain, then QM as you know it is badly wrong.
I am talking about why subjective experience exists given that the physical universe exists.
Interesting. How do you know that the physical universe exists, though? Could it be that your certainty about the physical universe has something to do with your subjective experience?
a mapping from the mathematical structure of physical systems
“The mathematical structure of physical systems” means either physical law, or else something so arbitrary that a large rock can be said to instantiate all human consciousnesses.
If you believe that we evolved systems for maintaining stable macroscopic quantum superposition without decoherence, and that we have not noticed this when we study the brain, then QM as you know it is badly wrong.
Evidence please. Quantum biology is an active research topic, and models of quantum computation differ in how resilient they are to decoherence.
So you do think there is a difference between physicalism and computationalism even if the Church-Turing-Deutsch principle is true? And this difference is something to do with a special status held by the real world vs. simulations of the real world? I’m trying to understand what these competing theories are but there seems to be a communication problem that means you are failing to convey them to me.
That’s what it means to say that physicalism is substrate-dependent. There is a (simple) psycho-physical law which states that subjective experience is implemented on a specific substrate.
It just so happens that evolution has invented some analog supercomputers called “brains” and optimized them for computational efficiency. At some point, it hit on a “trick” for running quantum computations with larger and larger state spaces, and started implementing useful algorithms such as reinforcement learning, aversive learning, perception, cognition etc. on this substrate. As it turns out, the most efficient physical implementations of such quantum algorithms have subjective experience as a side effect, or perhaps as a crucial building block. So subjective awareness got selected for and persisted in the population to this day.
It seems a fairly simple story to me. What’s wrong with it?
So is one of the properties of that specific substrate (the physical world) that it cannot be simulated by a Turing machine? I don’t know why you can’t just give a yes/no answer to that question. I’ve stated it explicitly enough times now that you just come across as deliberately obtuse by not answering it.
I think I’ve been fairly clear that I don’t deny the possibility that consciousness depends on non-computable physics. I don’t think it is the most likely explanation but it doesn’t seem to be clearly ruled out given our current understanding of the universe. Your story might be something close to the truth if the Church-Turing-Deutsch principle is false. It appears to me to be incoherent if it is true however.
I think the Church-Turing-Deutsch principle is probably true but I don’t think we can rule out the possibility that it is false. If it is true then it seems a simulation of a human running on a conventional computer would be just as conscious as a real human. If it is false then it is not possible to simulate a human being on a conventional computer and it therefore doesn’t make sense to say that such a simulation cannot be conscious because a simulation cannot be created. What if anything do you disagree with from those claims?
Because it implies the possibility of zombies, or for some other reason?
Basically, yes. Slightly more explicitly, it appears to say that two contradictory things are true: that a Turing machine can simulate every physical process but that there are properties arising from physical processes running directly on their ‘native’ hardware that do not arise when those same processes are simulated. That suggests either that the simulation is actually incomplete (it is missing inputs or algorithms that account for the difference) or that there is some kind of dualism going on: a mysterious and unidentifiable ‘something’ that accounts for consciousness existing in a human brain but not in a perfect simulation of a human brain.
If the missing something is not part of physics then we’re really back to dualism and not physicalism at all. It seems like an attempt to sneak dualism back in without admitting to being a dualist in polite company.
Is subjective experience a “property”? By assumption, all the features of subjective experience have physical correlates which are preserved by the simulation. It’s just that the ‘native’ process fits a “format” that allows it to actually be experienced, whereas the simulated version does not. It seems weird to call this a dualist theory when the only commonality is an insistence on taking the problem of subjective experience seriously.
Well, I don’t think it really matters what you call it but I assume we agree that it is a something. Do you believe that it is in principle possible to differentiate between an entity that has that something and an entity that does not?
This sounds like your answer to my previous question is ‘no’. So is your position that it is not possible in principle to distinguish between a simulation of a human brain and a ‘real’ human brain but that the latter differs in that it possesses a ‘something’ that is not a function of the laws of physics and is inaccessible to any form of investigation other than introspection by the inhabitant of that brain but that is nonetheless in some sense a meaningful distinction? That sounds a lot like dualism to me.
Perhaps not. ‘That something’ may be simply a model which translates the aforementioned physical properties into perceptual terms which are more familiar to us. But this begs the question of why we would be familiar with perception in the first place; “we have subjective experience, and by extension so does anything which is implemented in the same substrate as us” is a good way to escape that dilemma.
The whole point of physicalism is that subjective experience is a function of the laws of physics, and in fact a fairly low-level function. If you want to avoid any hint of dualism, just remove the “inhabitant” (a misnomer) and the “psycho-physical bridging laws” from the model and enjoy your purely physicalistic theory. Just don’t expect it to do a good job of talking about phenomenology or qualia: physicalist theories are just weird like that.
As the saying goes, those who do not know dualism are doomed to reinvent it, poorly. Beware this tendency.
Do you ever answer a direct question?
Are you saying that there is some extra law (on top of the physical laws that explain how our brains implement our cognitive algorithms) that maps our cognitive algorithms, or a certain way of implementing them, to consiousness? So that, in principal, the universe could have not had that law, and we would do all the same things, run all the same cognitive algorithms, but not be consious? Do you believe that p-zombies are conceptially possible?
The psycho-physical law is not really an extra law “on top of the laws of physics”, so much as a correspondence between quantum state spaces and subjective experiences—ideally, the correspondence would be as simple as possible.
You could build a version of the universe which was not endowed with any psycho-physical laws, but it’s not something anyone would ever experience; it would be one formal system plucked out seemingly at random from the set of computational structures. It is as logically possible as anything else, but whether it makes sense to regard such a bizarre thing as “conceptually possible” is another matter.
But would this universe look the same as our universe to an outside observer who cannot directly observe subjective experience, but only the physical states that subjective experience supposedly correspond to?
We’re assuming that physicalism is true, so yes it would look the same. The inhabitants would be p-zombies, but all physical correlates of subjective experience would exist.
So, since in this alternate universe without subjective experience, people have the same discussions about subjective experience as their analogs in this universe, the subjective experience is not the cause of these discussions. So what explains the fact the this physical stuff people are made out of, which only obeys physical laws and can’t be influenced by subjective experience, discusses subjective experience? Where did that improbability come from?
First of all, physical stuff can be influenced by the physical correlates of subjective experience. Since the zombie universe was obtained by removing subjective experience from an universe where it originally existed, it’s not surprising that these physical correlates would show some of the same properties.
The properties which subjective experience and its physical correlates have in this universe could be well explained by a combination of (1) anthropic principles (2) the psycho-physical bridging law (3) the properties of our perceptions and other qualia. Moreover, the fact that we’re having this discussion screens out the possibility that people might have no inclination at all to talk about subjective experience.
If the physical properties of the physical correlates of subjective experience are sufficient to explain why we talk about subject experience even without a bridging law, then why are they not enough to also explain the subjective experiences without a bridging law?
Subjective experience is self-evident enough to need no explanation. What needs to be explained is how its content as perceived by us (i.e. qualia, beliefs, thoughts etc.) relates to formally modeled physics: hence, the bridging law maps between the conceptual description and the complex quantum system which is physically implemented in the brain.
No, subjective experience is self-evident enough that we do not need to argue about whether it exists, we can easily agree that it does. (Though, you seem to believe that in the zombie world, we would incorrectly come to the same agreement.) But agreeing that something exists is not the same as understanding how or why it exists. This part is not self-evident and we disagree about it. You seem to believe that the explanation requires macroscopic quantum superpositions and some bringing law that somewhat arbitrarily maps these quantum superpositions onto subjective experiences. I believe that if we had sufficient computing power and knew fully the arrangement of neurons in a brain, we could explain it using only classical approximations of physics.
We don’t understand why, but then again we don’t know why anything exists. In practice, something as basic as subjective experience is always taken as a given. As for how, our inner phenomenology reveals far more about subjective experience than physics ever could.
Nevertheless, we do also want to know how the self might relate to our physical models; and contrary to what might be expected, macroscopic quantum superposition is actually the parsimonious hypothesis here for a wide variety of reasons.
Unless QM as we know it is badly wrong, it just doesn’t fit our models of physical reality that anything resembling “the self” would be instantiated in a hugely complicated classical system (a brain with an arrangement of brain regions and billions of neurons? Talk about an arbitrary bridging law!) as opposed to a comparatively simple quantum state.
Moreover, it is eminently plausible that evolution should have found some ways of exploiting quantum computation in the brain during its millions-of-years-long development. The current state of neuroscience is admittedly unsatisfactory, but this shouldn’t cause us to shed too much confidence.
I am talking about why subjective experience exists given that the physical universe exists. Are you being deliberately obtuse?
You are failing to address my actual position, which is that there is no arbitrary bridging law, but a mapping from the mathematical structure of physical systems to subjective experience, because that mathematical structure is the subjective experience, and it mathematically has to be that way. The explanation of why and how I am talking about is an understanding of that mathematical structure, and how physical systems can have that structure.
If you believe that we evolved systems for maintaining stable macroscopic quantum superposition without decoherence, and that we have not noticed this when we study the brain, then QM as you know it is badly wrong.
Interesting. How do you know that the physical universe exists, though? Could it be that your certainty about the physical universe has something to do with your subjective experience?
“The mathematical structure of physical systems” means either physical law, or else something so arbitrary that a large rock can be said to instantiate all human consciousnesses.
Evidence please. Quantum biology is an active research topic, and models of quantum computation differ in how resilient they are to decoherence.