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Why physics cannot explain consciousness
This continues the lively discussion in the consciousness megathread.

I have long believed that physics cannot explain consciousness. I now believe, possibly with foolish optimism, that I have a clear and convincing argument for my position.



Quote from: Democritus
INTELLECT: Ostensibly there is color, ostensibly sweetness, ostensibly bitterness, actually only atoms and the void.

SENSES: Poor intellect, do you hope to defeat us while from us you borrow your evidence? Your victory is your defeat.


Objective


My ultimate goal is to show that consciousness fills a gap in the physicalist account of the universe. Along the way, I will define "consciousness", show that intrinsic natures lie outside the purview of physics, and show that consciousness is intrinsic.


The intuition

Quote from: Bertrand Russell
It is obvious that a man who can see knows things which a blind man cannot; but a blind man can know the whole of physics. Thus the knowledge that other men have and he has not is not part of physics.

Consider a man who has been blind from birth. Could you explain to him, even in principle, what it is like to see? It seems that you could not, even if you could give him a complete description of physics. Unless his blindness were cured (or surgeons electrically stimulated his visual cortex), no knowledge of physical laws - the behavior of light, the structure of the eye, the patterns of neural firing in the brain - could acquaint him with the subjective experience of vision; for example, with the appearance of redness. He could only learn about vision "from the outside". If his blindness were suddenly cured, it seems that he would learn something new, something that physics alone could not teach him.

Why can't physics tell the blind man what things "look like"? What kind of information does the blind man acquire when he is cured? Before I can answer these questions, I need to be more precise.


The importance of defining "consciousness"


"Consciousness" is an extremely overloaded word. (George Miller complained: "'Consciousness' is a word worn smooth by a million tongues.") Depending on context, it can mean "wakefulness", "attentiveness", "self-awareness", "metacognition", or many other things. To avoid ambiguity and confusion, I must specify my meaning.

While each is interesting in its own right, the aforementioned meanings are not the subject of this discussion. I will restrict my attention to the word's most slippery meaning - the meaning that the following quotes seem to be getting at:

Quote from: Stuart Sutherland
The term is impossible to define except in terms that are unintelligible without a grasp of what consciousness means. Many fall into the trap of equating consciousness with self-consciousness - to be conscious it is only necessary to be aware of the external world. Consciousness is a fascinating but elusive phenomenon: it is impossible to specify what it is, what it does, or why it has evolved. Nothing worth reading has been written on it.

Quote from: Edward Witten
I tend to think that the workings of the conscious brain will be elucidated to a large extent. Biologists and perhaps physicists will understand much better how the brain works. But why something that we call consciousness goes with those workings, I think that will remain mysterious. I have a much easier time imagining how we understand the Big Bang than I have imagining how we can understand consciousness.


My definition of "consciousness"


Stuart Sutherland's pessimism notwithstanding, I will now define consciousness from my perspective. As it turns out, this is relatively easy. (It is defining anything else that is difficult.) It only seems difficult because I habitually think of myself in the third person, forgetting that scientific inquiry starts with the self and the senses.

It is true that something exists: so much is certain. The world is not nothing. (Anyone who disagrees is beyond help.) What is it whose existence is certain? Following Descartes' example, let me adopt a position of extreme skepticism. At the moment, I seem to be typing on a keyboard, but it is not certain that I am typing on a keyboard. I might be insane, and what I believe to be a keyboard might actually be a ham sandwich; I might be dreaming, and not actually moving my fingers; or I might be a brain in a vat, and all of my beliefs, true and false, might be programmed by a mad scientist. What is beyond dispute, however, is that I seem to be typing on a keyboard. Even if I am not actually typing on a keyboard, the appearance of typing is a given. This applies to every other part of my immediate experience: the appearance of seeing a computer, the appearance of sitting in a chair, the appearance of being human. The computer, the chair, and my body do exist as parts of my immediate experience. Whether they exist in any other sense is unclear.

I can now define this consciousness to be the collection of all things whose existence is certain: everything of which I am currently aware. Because these are the only things whose existence is certain, it is conceivable that nothing else exists. In this worldview (solipsism), defining something outside of consciousness is impossible. Despite solipsism's unfalsifiability and supreme parsimony, I take a leap of faith: I assume the existence of things that are outside of my awareness. Perhaps most importantly, I assume the existence of other consciousnesses. Although I cannot access them directly - because they are not this consciousness, and are therefore absent in the solipsistic worldview - I can easily imagine them by way of analogy. I simply "put myself in someone else's shoes".

The preceding argument has been framed as a monologue, applying only to me. But the reader can make a similar argument. (By saying this, I am again assuming that other consciousnesses exist - an assumption that I find natural, and that I assume other consciousnesses also find natural.)


Fundamental limitations of physics


From a philosophical standpoint, I can worry about "what is real". Is the universe (as I understand it) some kind of simulation? Even more counter-intuitively, is "my" consciousness the only thing that exists? Fortunately, these concerns do not invalidate the scientific method. Regardless of its nature, the universe appears to follow certain rules, which I call "physical laws". Inductive reasoning allows me to guess these rules, then use my guesses to make predictions.

By the same token, physical laws are silent as to the nature of the things that they describe. Physics only deals with causal relationships. For example, it only describes how fundamental particles behave, not what fundamental particles are. (Niels Bohr: "Isolated material particles are abstractions, their properties being definable and observable only through their interaction with other systems.") One analogy is the game of chess. Whether I play chess with a wooden board and wooden pieces, with a vinyl board and plastic pieces, or in my mind, I am still playing chess, because the rules of chess do not depend on their implementation. Another analogy (given by Hedda Hassel Mørch) is that physical laws are the universe's "software". If the universe is some kind of simulation, then physics has nothing to say about the simulation's underlying "hardware".

The reason for all of this is simple: mathematics is the language of physics, and the power of mathematics lies in its abstraction. At the roots of mathematical theories are undefined terms (e.g. "set" in set theory), whose only relevant properties (e.g. "membership") are relational. When these terms are given physical interpretations, mathematics continues to describe their relationships - and nothing more.

 
Re: Why physics cannot explain consciousness
The existence and importance of intrinsic natures


What are the basic entities of physics, in and of themselves, beyond their behavior? What are their intrinsic natures? (Analogously, what are the chess pieces made of? What is the universe's hardware?) Physics can, in principle, tell me how a physical entity affects the rest of the world - that is, other physical entities - but I am not asking about a relationship. I am asking about a physical entity in isolation. Since physics is only concerned with relationships, I must look elsewhere for an answer.

At this point, the diehard physicalist has a possible rebuttal: that there are no intrinsic natures. In this worldview, the basic entities of physics simply are the sums of their causal properties, and have no further reality or structure. The universe has no underlying hardware; it's "relations all the way down", and the relationships describable by physics are the only things that exist.

Is this claim reasonable? First of all, note that it is a metaphysical claim. If they exist, intrinsic natures have no effect on physics; therefore, no argument for or against their existence can come from physics. On metaphysical grounds, the only obvious argument against their existence is Occam's Razor. So what are some metaphysical arguments for their existence?

One argument is that fundamental non-relational entities are necessary to avoid circularity or infinite regress. A relation involves "things" that are being related; a worldview that consists entirely of relations is structurally unsound. Just as mathematical theories need undefined terms, so does physics.

Quote from: Bertrand Russell
There are many possible ways of turning some things hitherto regarded as 'real' into mere laws concerning the other things. Obviously there must be a limit to this process, or else all the things in the world will merely be each other's washing.

Another argument is that the claim, "relationships describable by physics are the only things that exist", is extremely strong. It seems indistinguishable from Max Tegmark's mathematical universe hypothesis, which claims that mathematics not only describes the universe, but is the universe: a claim that most people find unpalatable. Mathematics is merely an abstraction, a framework. (As Alfred Korzybski phrased it, "the map is not the territory".) It describes rules for interactions, but says nothing about their instantiation, or a "current state of affairs". If Tegmark is correct, then what distinguishes abstract mathematical structures - for example, the theory of inaccessible cardinals, which do not seem to exist in the "real world" - from concrete ones (ones that actually exist)?

Quote from: Stephen Hawking
Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe? The usual approach of science of constructing a mathematical model cannot answer the question of why there should be a universe for the model to describe. Why does the universe go to all the bother of existing?

The natural answer to these questions is "intrinsic natures": the properties of the universe that ground reality, and that mathematics does not describe (whatever these may be). But this option is not available to someone who metaphysically declares that all properties are "observable" properties.

The diehard physicalist has another possible rebuttal. Assuming that intrinsic natures do exist, why should we care about them? By definition, they have no causal power, at least in the usual sense. (To use the chess analogy: even though the rules of chess do not depend on their implementation, some kind of implementation is necessary to play the game.) It seems idle to speculate about things that have no observable effects on the world.

Of course, the same objection can be raised against the entirety of metaphysics, and philosophy in general. As useful as it is, science has no handle on the really big questions: the nature of knowledge, the nature of reality, why there is something rather than nothing. These topics are arguably of supreme importance, so saying that you simply don't care about them is very odd.

Another good reason to care about intrinsic natures is that consciousness is intrinsic, as I will now show - thereby settling the questions of existence and importance in one fell swoop.


Consciousness is intrinsic


Why is consciousness (as previously defined) intrinsic, in a sense that precludes any description by physics?

First, consciousness cannot be something relational, because it can be imagined in isolation. It exists by definition, and in the unfalsifiable solipsistic worldview, nothing else does. If consciousness were a relationship describable by physics, then its existence would entail the existence of things that were being related - namely, physical entities outside of consciousness. But such an entailment is impossible, because the language of physics is compatible with solipsism; the laws of physics can be expressed entirely within consciousness, which makes consciousness itself "too big" for physics to describe it. Fortunately, less formal languages (such as English) can express things that physics cannot. Otherwise, the field of metaphysics would not exist.

Quote from: Erwin Schrödinger
The reason why our sentient, percipient and thinking ego is met nowhere within our scientific world picture can easily be indicated in seven words: because it is itself that world picture. It is identical with the whole and therefore cannot be contained in it as a part of it.

Second, again by definition, consciousness tells me that something specific - for example, the appearance of typing on a keyboard - is actually happening at this moment. This is a statement that no laws of physics can ever imply, because the laws of physics are constant. As discussed earlier, physics defines a set of rules, but says nothing about an instantiation of those rules, or "current state of affairs". (Peter Hankins calls it "haecceity": the particularity and actuality of experience, which are unavoidably absent in any general, abstract theory.) Consciousness is concrete in a way that physics is not, which makes it a strong candidate for the universe's underlying "hardware", or Stephen Hawking's "fire" - the properties of the universe that ground reality, and that mathematics does not describe.


Explaining the intuition


Let me revisit the man who has been blind from birth. Without experiencing it himself, he cannot know what vision "is". He can learn about its mathematical aspects - the behavior of light, and so on - but all of this knowledge is abstract, ultimately reducible to relationships between undefined terms. Since the interpretations of these terms are irrelevant to mathematics (just as intrinsic natures are irrelevant to physics), the interpretations must be based on concrete non-mathematical knowledge. The only source of such knowledge is consciousness. But the blind man's consciousness has never contained visual information, so his interpretations will be different from those of a sighted person; for example, his interpretation of a "point" in space, if points are treated as basic. Even if two people use the same model of physics, their interpretations can (and arguably must) differ.

When the blind man's condition is cured, he does not discover a new physical law. Rather, he learns about something that no abstract theory can ever capture: the reality or intrinsic nature of vision, as a content of consciousness. This affects his interpretations of physical laws. The information that he acquires is not physical, but metaphysical. Rather than having a "map" of vision, he now knows the "territory": a part of reality that was previously inaccessible to him.

This also explains the strange intuition - "the zombic hunch", in Daniel Dennett's words - that someone could be physically identical to a conscious person without being conscious. This is as nonsensical as the idea that a computer program could run without any hardware to implement it, but it seems plausible because it contains a grain of truth. Physical descriptions inevitably leave out intrinsic qualities, and the only glimpse of these qualities comes from consciousness. Hence the belief (held by Edward Witten, for example) that science can address many aspects of cognition, but not this one.


Conclusion


People have called it "the most familiar and most mysterious aspect of our lives" (Max Velmans & Susan Schneider), "the most important topic in the philosophy of mind" (David Chalmers), and "just about the last surviving mystery" (Daniel Dennett). Physicalists say that it can be explained by physics. If by "it", they mean something like "wakefulness" or "attentiveness", then they are probably right. If they mean "consciousness" as previously defined, then they are probably wrong. This meaning of consciousness is tied to the nature of reality, which places it outside the scope of physics.

Is consciousness precisely what I mean by "intrinsic nature"? Does everything in the universe have some form of consciousness (a view known as "panpsychism")? If the universe is some kind of simulation, and if consciousness is its hardware, does consciousness have causal power "outside" the simulation (in the same sense that a chess piece's implementation does not affect the game, but does affect the world outside the game)? These are questions for philosophers, not for physicists.

 

Offline The E

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Re: Why physics cannot explain consciousness
Counterpoint: if everything a computer does can be explained in terms of physical interactions, why can't I use the same rule set to explain how human brains work?

As far as I am concerned, you haven't shown a strong reason for why the subjective experience of consciousness cannot arise from strictly physical interactions.
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Offline The E

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Re: Why physics cannot explain consciousness
Quote
Consider a man who has been blind from birth. Could you explain to him, even in principle, what it is like to see? It seems that you could not, even if you could give him a complete description of physics. Unless his blindness were cured (or surgeons electrically stimulated his visual cortex), no knowledge of physical laws - the behavior of light, the structure of the eye, the patterns of neural firing in the brain - could acquaint him with the subjective experience of vision; for example, with the appearance of redness. He could only learn about vision "from the outside". If his blindness were suddenly cured, it seems that he would learn something new, something that physics alone could not teach him.

All of this is true.

It is also irrelevant to the question of whether or not consciousness as a process can be modelled in terms of physical interactions.

You quote Witten, but neither he nor you offer any concrete explanation why consciousness is not describable in physics terms. I would, in fact, say that based on your quote, Witten considers consciousness to be too complex to be describable in detail, not that it is indescribable by its nature; That, to me, is an important difference.

Quote
At this point, the diehard physicalist has a possible rebuttal: that there are no intrinsic natures. In this worldview, the basic entities of physics simply are the sums of their causal properties, and have no further reality or structure. The universe has no underlying hardware; it's "relations all the way down", and the relationships describable by physics are the only things that exist.

Is this claim reasonable? First of all, note that it is a metaphysical claim. If they exist, intrinsic natures have no effect on physics; therefore, no argument for or against their existence can come from physics. On metaphysical grounds, the only obvious argument against their existence is Occam's Razor. So what are some metaphysical arguments for their existence?

One argument is that fundamental non-relational entities are necessary to avoid circularity or infinite regress. A relation involves "things" that are being related; a worldview that consists entirely of relations is structurally unsound. Just as mathematical theories need undefined terms, so does physics.

You're doing that thing again where you are making a definition and then argue based on its correctness without offering any strong evidence for why that definition is correct.

Quote
First, consciousness cannot be something relational, because it can be imagined in isolation.

I think the above quote exemplifies this issue. "Physics describes relationships, Consciousness is not a relationship, therefore consciousness is not a physical thing, q.e.d.". You're making several mistakes here: One is that Physics very definitely is not just the study of the relationships between discrete items, but also concerns itself with those discrete items themselves.
Secondly, you define consciousness as not being "relational", based purely on the fact that you can imagine consciousness existing without a substrate to run on. Imagination is a wonderful thing, one can spend eternities imagining qualia divorced from anything that might be considered physical reality, but that alone does not say anything about whether or not imagination can happen without a substrate (in our case, the human brain). DeepDream dreams of dogs and fishes, even in the absence of dogs and fishes in its input; that fact alone does not render DeepDream inexplicable (it is also provable that DeepDream only dreams when actively run on actual computing hardware!).
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Let there be monsters and let there be pain
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Offline The E

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Re: Why physics cannot explain consciousness
Also, Ghyl, you ignore one of the fundamental issues brought up in the last thread: We can prove, quite easily even, that consciousness cannot be easily divided from its substrate. In fact, given that we have hard evidence of physical alterations in the substrate affecting consciousness and that the substrate is altered by the process of consciousness acting upon it (as demonstrated by the neurological changes you undergo when learning something new), we can make the inference that consciousness and brains are inextricably linked: Without a hardware platform, you have no consciousness; without consciousness, the hardware lies dormant.
Let there be light
Let there be moon
Let there be stars and let there be you
Let there be monsters and let there be pain
Let us begin to feel again
--Devin Townsend, Genesis

 

Offline Colonol Dekker

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Re: Why physics cannot explain consciousness
I always equate consciousness as music,  and the brain as a an old vinyl record.  When the record isn't spinning the music is still there, but if you scratch that record it'll change the song and it'll never be the same.
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Offline Luis Dias

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Re: Why physics cannot explain consciousness
Two quick points.

First, and apart from The_E's insightful scalpings, I'm personally more inclined to a materialistic explanation for consciousness, and how it slowly arises from a continuous development of things that start to coalesce into selves, first by thermodynamics (hurricanes are a thing in itself), then on to material selves (viruses, protobacteria), then on to multicellular entities that work between themselves into an original self, then onto the creation of brains, which reflect on the self of the body and then at last into consciousness, which reflect into the reflection itself.

In this regard, there is no end in sight for the development of even more "consciencious" consciences, and just like blind people can't know what sight is, we can enumerate an infinity of qualia that we are deprived from by natural design, that at least in principle we could develop technologically in the future. Such a conscience would "grow" exponentially, or at least we can posit its possibility.

Second, I was having Evangelion vibes from your text, and that was neat.

 
Re: Why physics cannot explain consciousness
Skimming Ghyl’s post it seems like an awful lot of sophistry dressing up the tautology that his worldview is almost axiomatically dualist and cannot even really recognise a monist, materialist one.
The good Christian should beware of mathematicians, and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of Hell.

 
Re: Why physics cannot explain consciousness
If you acknowledge the existence of consciousness other than your own you are essentially accepting a physical nature of consciousness. You can only observe other consciousnesses by their physical properties; you have no access to their ‘essential’ subjective nature.
The good Christian should beware of mathematicians, and all those who make empty prophecies. The danger already exists that the mathematicians have made a covenant with the devil to darken the spirit and to confine man in the bonds of Hell.

  
Re: Why physics cannot explain consciousness
Counterpoint: if everything a computer does can be explained in terms of physical interactions, why can't I use the same rule set to explain how human brains work?

As far as I am concerned, you haven't shown a strong reason for why the subjective experience of consciousness cannot arise from strictly physical interactions.
Also, Ghyl, you ignore one of the fundamental issues brought up in the last thread: We can prove, quite easily even, that consciousness cannot be easily divided from its substrate. In fact, given that we have hard evidence of physical alterations in the substrate affecting consciousness and that the substrate is altered by the process of consciousness acting upon it (as demonstrated by the neurological changes you undergo when learning something new), we can make the inference that consciousness and brains are inextricably linked: Without a hardware platform, you have no consciousness; without consciousness, the hardware lies dormant.

You seem to be arguing with a strawman. I believe that everything a computer does (your word choice is excellent) and everything a brain does can be explained in terms of physical interactions; I believe that the subjective experience of consciousness arises from physical interactions; and I believe that consciousness and the brain are inextricably linked. None of these things are in dispute.

Quote
Consider a man who has been blind from birth. Could you explain to him, even in principle, what it is like to see? It seems that you could not, even if you could give him a complete description of physics. Unless his blindness were cured (or surgeons electrically stimulated his visual cortex), no knowledge of physical laws - the behavior of light, the structure of the eye, the patterns of neural firing in the brain - could acquaint him with the subjective experience of vision; for example, with the appearance of redness. He could only learn about vision "from the outside". If his blindness were suddenly cured, it seems that he would learn something new, something that physics alone could not teach him.

All of this is true.

It is also irrelevant to the question of whether or not consciousness as a process can be modelled in terms of physical interactions.

You quote Witten, but neither he nor you offer any concrete explanation why consciousness is not describable in physics terms. I would, in fact, say that based on your quote, Witten considers consciousness to be too complex to be describable in detail, not that it is indescribable by its nature; That, to me, is an important difference.

If you acknowledge that some aspects of the mind are incommunicable, and cannot be grasped solely by studying physics, then I think we are mostly in agreement.

Where are you pulling "complexity" from? Witten's comparison with the Big Bang suggests something entirely different: a fundamental limit of human knowledge.

You're doing that thing again where you are making a definition and then argue based on its correctness without offering any strong evidence for why that definition is correct.

I have no idea which definition you're talking about, or what you mean by "correct".

One is that Physics very definitely is not just the study of the relationships between discrete items, but also concerns itself with those discrete items themselves.

This is news to me. I suspect that it would also be news to Niels Bohr, were he still alive. Can you give an example of something that physics describes beyond relationships?

Another analogy might be helpful here. Imagine Conway's Game of Life running on a futuristic supercomputer, with a pattern so complex that it contains intelligent organisms. (This is not as far-fetched as it sounds; see digital physics.) For these organisms, the laws of physics would simply be the rules of Life, which would describe every structure and process in the universe.

But the rules of Life would not tell the organisms what a "cell" is. They would not know that they lived in a supercomputer, or how the supercomputer implemented "cells".

Secondly, you define consciousness as not being "relational", based purely on the fact that you can imagine consciousness existing without a substrate to run on. Imagination is a wonderful thing, one can spend eternities imagining qualia divorced from anything that might be considered physical reality, but that alone does not say anything about whether or not imagination can happen without a substrate (in our case, the human brain).

The word "imagined" is, of course, vague. I clarified my meaning immediately afterward, and in Schrödinger's quote.



Skimming Ghyl’s post it seems like an awful lot of sophistry dressing up the tautology that his worldview is almost axiomatically dualist and cannot even really recognise a monist, materialist one.

Huh? Dualism? My position is closest to Russellian monism.

If you are a monist (like me), then the question arises: what is this "stuff" that makes up reality? Physics can tell us nothing about this stuff, but consciousness offers a glimpse.

You can only observe other consciousnesses by their physical properties; you have no access to their ‘essential’ subjective nature.

You are right that the essential nature of other consciousnesses is inaccessible, and therefore outside the scope of physics. But I do have access to my consciousness - which is why consciousness offers a glimpse of reality's essential nature.