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Shadows of the Mind: A Search for the Missing Science of Consciousness
A New York Times bestseller when it appeared in 1989, Roger Penrose's The Emperor's New Mind was universally hailed as a marvelous survey of modern physics as well as a brilliant reflection on the human mind, offering a new perspective on the scientific landscape and a visionary glimpse of the possible future of science. Now, in Shadows of the Mind, Penrose offers another exhilarating look at modern science as he mounts an even more powerful attack on artificial intelligence. But perhaps more important, in this volume he points the way to a new science, one that may eventually explain the physical basis of the human mind.
Penrose contends that some aspects of the human mind lie beyond computation. This is not a religious argument (that the mind is something other than physical) nor is it based on the brain's vast complexity (the weather is immensely complex, says Penrose, but it is still a computable thing, at least in theory). Instead, he provides powerful arguments to support his conclusion that there is something in the conscious activity of the brain that transcends computation—and will find no explanation in terms of present-day science. To illuminate what he believes this “something” might be, and to suggest where a new physics must proceed so that we may understand it, Penrose cuts a wide swathe through modern science, providing penetrating looks at everything from Turing computability and Gödel's incompleteness, via Schrödinger's Cat and the Elitzur-Vaidman bomb-testing problem, to detailed microbiology. Of particular interest is Penrose's extensive examination of quantum mechanics, which introduces some new ideas that differ markedly from those advanced in The Emperor's New Mind, especially concerning the mysterious interface where classical and quantum physics meet. But perhaps the most interesting wrinkle in Shadows of the Mind is Penrose's excursion into microbiology, where he examines cytoskeletons and microtubules, minute substructures lying deep within the brain's neurons. (He argues that microtubules—not neurons—may indeed be the basic units of the brain, which, if nothing else, would dramatically increase the brain's computational power.) Furthermore, he contends that in consciousness some kind of global quantum state must take place across large areas of the brain, and that it is within microtubules that these collective quantum effects are most likely to reside.
For physicists to accommodate something that is as foreign to our current physical picture as is the phenomenon of consciousness, we must expect a profound change—one that alters the very underpinnings of our philosophical viewpoint as to the nature of reality. Shadows of the Mind provides an illuminating look at where these profound changes may take place and what our future understanding of the world may be.
Penrose contends that some aspects of the human mind lie beyond computation. This is not a religious argument (that the mind is something other than physical) nor is it based on the brain's vast complexity (the weather is immensely complex, says Penrose, but it is still a computable thing, at least in theory). Instead, he provides powerful arguments to support his conclusion that there is something in the conscious activity of the brain that transcends computation—and will find no explanation in terms of present-day science. To illuminate what he believes this “something” might be, and to suggest where a new physics must proceed so that we may understand it, Penrose cuts a wide swathe through modern science, providing penetrating looks at everything from Turing computability and Gödel's incompleteness, via Schrödinger's Cat and the Elitzur-Vaidman bomb-testing problem, to detailed microbiology. Of particular interest is Penrose's extensive examination of quantum mechanics, which introduces some new ideas that differ markedly from those advanced in The Emperor's New Mind, especially concerning the mysterious interface where classical and quantum physics meet. But perhaps the most interesting wrinkle in Shadows of the Mind is Penrose's excursion into microbiology, where he examines cytoskeletons and microtubules, minute substructures lying deep within the brain's neurons. (He argues that microtubules—not neurons—may indeed be the basic units of the brain, which, if nothing else, would dramatically increase the brain's computational power.) Furthermore, he contends that in consciousness some kind of global quantum state must take place across large areas of the brain, and that it is within microtubules that these collective quantum effects are most likely to reside.
For physicists to accommodate something that is as foreign to our current physical picture as is the phenomenon of consciousness, we must expect a profound change—one that alters the very underpinnings of our philosophical viewpoint as to the nature of reality. Shadows of the Mind provides an illuminating look at where these profound changes may take place and what our future understanding of the world may be.
457 pages, Hardcover
First published January 1, 1994
155 people are currently reading
4508 people want to read
About the author
Roger Penrose
106 books1,330 followersSir Roger Penrose (8 August 1931 - ) is a British mathematician, mathematical physicist, philosopher of science and Nobel Laureate in Physics.
He is Emeritus Rouse Ball Professor of Mathematics in the University of Oxford, an emeritus fellow of Wadham College, Oxford, and an honorary fellow of St John's College, Cambridge, and University College London.
Penrose has contributed to the mathematical physics of general relativity and cosmology. He has received several prizes and awards, including the 1988 Wolf Prize in Physics, which he shared with Stephen Hawking for the Penrose–Hawking singularity theorems, and the 2020 Nobel Prize in Physics "for the discovery that black hole formation is a robust prediction of the general theory of relativity".
He is Emeritus Rouse Ball Professor of Mathematics in the University of Oxford, an emeritus fellow of Wadham College, Oxford, and an honorary fellow of St John's College, Cambridge, and University College London.
Penrose has contributed to the mathematical physics of general relativity and cosmology. He has received several prizes and awards, including the 1988 Wolf Prize in Physics, which he shared with Stephen Hawking for the Penrose–Hawking singularity theorems, and the 2020 Nobel Prize in Physics "for the discovery that black hole formation is a robust prediction of the general theory of relativity".
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October 8, 2023
The argument is simple. There are mathematical problems that can't be solved using algorithms - non-computable problems. If you device an algorithm to solve that kind of problems, and let a computer run the algorithm, it would never stop. Yet the human mathematician is able to solve that kind of problems. Computational neuroscience (and Artificial Intelligence) treats the brain as a computer: either there is a neuronal signal or not, very much similar to the 0 and 1 scheme. But that algorithmic representation can't be truly faithful to what's really going on in the mathematician's brain. There must be a non-computable ingredient.
Penrose argues then, that there's a deeper level of information processing in the brain, deeper than neural networks. Microtubules is the best candidate for that. Think of a unicellular organism, like an amoeba. How does it know where to go and what to do? It has no nervous system, not even a single neuron. Yet it does what it does, by the means of these cellular automata. One more thing: it appears that things at that molecular level behave according to the strange laws of quantum mechanics, providing the non-computable ingredient.
This is an extraordinary approach to the problem of consciousness, and Penrose is a humble man (although in one of his interviews he pointed out to the interviewer that he should be called "Sir" Roger Penrose!) who doesn't claim to have solved the mystery of consciousness. He clearly states that the argument is strong at least for the quality of understanding. And that other qualities of consciousness like feeling, attention, imagination can't be simply explained by algorithms (only), or be regarded as phenomena emerging out of complexity (the cerebellum is as complex as the cerebrum yet it's totally automated and unconscious).
Penrose argues then, that there's a deeper level of information processing in the brain, deeper than neural networks. Microtubules is the best candidate for that. Think of a unicellular organism, like an amoeba. How does it know where to go and what to do? It has no nervous system, not even a single neuron. Yet it does what it does, by the means of these cellular automata. One more thing: it appears that things at that molecular level behave according to the strange laws of quantum mechanics, providing the non-computable ingredient.
This is an extraordinary approach to the problem of consciousness, and Penrose is a humble man (although in one of his interviews he pointed out to the interviewer that he should be called "Sir" Roger Penrose!) who doesn't claim to have solved the mystery of consciousness. He clearly states that the argument is strong at least for the quality of understanding. And that other qualities of consciousness like feeling, attention, imagination can't be simply explained by algorithms (only), or be regarded as phenomena emerging out of complexity (the cerebellum is as complex as the cerebrum yet it's totally automated and unconscious).
June 24, 2014
First and foremost Penrose presents the best argument against computer-simulated human intelligence I’ve heard to date. In fact it is the only argument that I know of that holds water (and I think by now I have heard them all – from Searle’s chinese room to the fundamental energy limitations of recursive simulation models). The mechanics and technical details of the argument get a little complex (Penrose approach is very systematic, often formal, and quite exhaustive - a large spectrum of mathematical, logical and philosophical corner cases are covered) but broad strokes are easy enough to follow.
The argument runs as follows. Consider math, which in theory should be the simplest thing for computer to “understand” before we even get to more complicated subjective areas such as emotions, qualia, free will etc. Then use Godel’s incompleteness theorem to show that regardless of how you pick your initial set of axioms (to be fed into the computer) there will exist mathematical statements that will be true, given the axioms, but will not be computable (in the church-turing sense) from those axioms. The truthfulness of those mathematical statements can be ascertained by humans but not by universal turing machines (i.e. computers). In other words there is something to human understanding that allows it to determine truthfulness/falsehood of statements and transcend the axiomatic rules from which such statements were derived from. It is exactly that kind of understanding that computers lack. Now, of course, to get to this point Penrose had to quickly cover a lot of ground – Turing machines, Church-Turing thesis, computability, decidability, (non)determinism, chaos, halting problems, tiling problems, discrete vs continuous computation, Godel’s theorem etc. It is a great refresher for those familiar with the subject matter and a nice introduction to those who aren’t.
The second half of the book looks for a non-computational yet scientific basis for human intelligence. Here Penrose moves into a brief overview of quantum mechanics (QM) which was quite fantastic actually (I dreamed of Schrodinger’s cat for a couple of nights), he also shows where QM breaks down and where its inconsistencies with general relativity get manifested. Absolutely fascinating overview of the field and its conundrums. No surprises here - we all know TOE is still work in progress and Penrose view is that it is QM that would need to be radically modified to be consistent with relativity, not the other way around.
Anyway, QM itself is very well-defined, precise and unambiguous but it is in its transition to non-quantum reality via state vector reduction where quite a few difficulties arise. Or to put it simply QM is perfectly well-defined (i.e. quantum coherence is indeed coherent) till the moment an observer is introduced. But in the end the author brings us to Hameroff-Penrose theory of consciousness that is linked to OR (objective reduction) of a wave function. And in the brain this non-computational process takes place not among the neurons themselves but in cytoskeleton microtubules (within neurons). Voila – we arrive at scientific non-computational basis for human understanding/consciousness
What can I say – recruiting Godel to drive a solid very scientific nail through the heart of hard AI (part one of the book) was very very nicely done and just for that the book gets five stars. A gallop through QM and its difficulties was a bit masochistic but I did enjoy it. As far as microtubules – clearly highly speculative but Penrose says so himself at the outset, so I suppose you can take it or leave it. Overall though this is one of the more rewarding books I’ve read in recent and not-so-recent memory; if you are even marginally interested in the subject matter reading this one should be a no-brainer.
The argument runs as follows. Consider math, which in theory should be the simplest thing for computer to “understand” before we even get to more complicated subjective areas such as emotions, qualia, free will etc. Then use Godel’s incompleteness theorem to show that regardless of how you pick your initial set of axioms (to be fed into the computer) there will exist mathematical statements that will be true, given the axioms, but will not be computable (in the church-turing sense) from those axioms. The truthfulness of those mathematical statements can be ascertained by humans but not by universal turing machines (i.e. computers). In other words there is something to human understanding that allows it to determine truthfulness/falsehood of statements and transcend the axiomatic rules from which such statements were derived from. It is exactly that kind of understanding that computers lack. Now, of course, to get to this point Penrose had to quickly cover a lot of ground – Turing machines, Church-Turing thesis, computability, decidability, (non)determinism, chaos, halting problems, tiling problems, discrete vs continuous computation, Godel’s theorem etc. It is a great refresher for those familiar with the subject matter and a nice introduction to those who aren’t.
The second half of the book looks for a non-computational yet scientific basis for human intelligence. Here Penrose moves into a brief overview of quantum mechanics (QM) which was quite fantastic actually (I dreamed of Schrodinger’s cat for a couple of nights), he also shows where QM breaks down and where its inconsistencies with general relativity get manifested. Absolutely fascinating overview of the field and its conundrums. No surprises here - we all know TOE is still work in progress and Penrose view is that it is QM that would need to be radically modified to be consistent with relativity, not the other way around.
Anyway, QM itself is very well-defined, precise and unambiguous but it is in its transition to non-quantum reality via state vector reduction where quite a few difficulties arise. Or to put it simply QM is perfectly well-defined (i.e. quantum coherence is indeed coherent) till the moment an observer is introduced. But in the end the author brings us to Hameroff-Penrose theory of consciousness that is linked to OR (objective reduction) of a wave function. And in the brain this non-computational process takes place not among the neurons themselves but in cytoskeleton microtubules (within neurons). Voila – we arrive at scientific non-computational basis for human understanding/consciousness
What can I say – recruiting Godel to drive a solid very scientific nail through the heart of hard AI (part one of the book) was very very nicely done and just for that the book gets five stars. A gallop through QM and its difficulties was a bit masochistic but I did enjoy it. As far as microtubules – clearly highly speculative but Penrose says so himself at the outset, so I suppose you can take it or leave it. Overall though this is one of the more rewarding books I’ve read in recent and not-so-recent memory; if you are even marginally interested in the subject matter reading this one should be a no-brainer.
May 12, 2016
Penrose, Gödel teoerimi üzerinden yapay zekanın hesaplanabilir bir etkinlikle oluşturulamayacağını söylerken aslında yapay zeka mümkün değil demiyor. Penrose'un ne demek istediğini anlamak için bu kitabı çok dikkatli okumak gerekir. Felsefecilerin Penrose'un argümanını tam olarak kavrayamadıkları kanaatindeyim.
June 9, 2015
Penrose, while more famous, does not do as well at popularizing the heady physics and mathemathics in this area as Barrow and Tipler (which see elsewhere in this list). His reasoning is too tortured and formula-heavy for me, whom I consider an advanced popular reader.
However, he does reach the deep conclusion that "whatever brain activity is responsible for consciousness . . . It must depend upon a physics that lies beyond computational simulation (p. 411)." Instead of resorting to the mind as mystical or mysterious, Penrose postulates that consciousness, while uncalculable, is still physical, perhaps in an interaction in the brain between classical physics and quantum physics not yet discovered or understood. Penrose points to the possibility of "microtubules" (part of the cytoskeleton that exist even in single-cell paramecium--and seem to give that cell some level of understanding!) that form nuerons at the quantum level being the answer to this current quandary:
"Accordingly, the neuron level of description that provides the currently fashionable picture of the brain and mind is a mere shadow of the deeper level of cytoskeletal action--and it is at this deeper level where we must seek the physical basis of mind!"
That Penrose only gets to this statement on p. 376 of this heavy tome is part of the problem with this book.
However, he does reach the deep conclusion that "whatever brain activity is responsible for consciousness . . . It must depend upon a physics that lies beyond computational simulation (p. 411)." Instead of resorting to the mind as mystical or mysterious, Penrose postulates that consciousness, while uncalculable, is still physical, perhaps in an interaction in the brain between classical physics and quantum physics not yet discovered or understood. Penrose points to the possibility of "microtubules" (part of the cytoskeleton that exist even in single-cell paramecium--and seem to give that cell some level of understanding!) that form nuerons at the quantum level being the answer to this current quandary:
"Accordingly, the neuron level of description that provides the currently fashionable picture of the brain and mind is a mere shadow of the deeper level of cytoskeletal action--and it is at this deeper level where we must seek the physical basis of mind!"
That Penrose only gets to this statement on p. 376 of this heavy tome is part of the problem with this book.
Read
January 5, 2015 Penrose's conclusions imply that there is a separate mental world, grounded in the physical world, and there is also another separate world, that of abstract ideas.
The book is clearly divided in two parts,
The first part is a proof that traditional Physics is not adequate to explain consciousness. The second part uses Quantum Theory to draft a theory of consciousness.
Penrose starts his argument by stating that classical Physics is inadequate to explain consciousness.
Somehow this relates to Goedel's theorem, which puts a limit to what a Turing machine can do, a limit that does not apply to the human mind;
Consciousness must be a quantum phenomenon because neurons are too big to account for consciousness. Inside neurons there is a cytoskeleton, the structure that holds cells together, whose microtubules (hollow protein cylinders 25-nanometers in diameter)
control the function of synapses.
Penrose believes that consciousness is a manifestation of the quantum cytoskeletal state and its interplay between quantum and classical levels of activity.
Subjective reduction is what happens
when an observer measures a quantity in a quantum system:
the system is not in any specific state ,the system is in a "superposition" of possible states.
until it is observed,
the observation causes the system to reduce (or "collapse")
to a specific state.
This is the only reduction known to traditional Quantum Theory.
Objective reduction is a Penrose discovery, part of his attempt at unifying Relativity Theory and Quantum Theory.
Super positioned states each have their own spacetime geometries.
Under special circumstances, which microtubules are suitable for, the separation of spacetime geometry of the superpositioned states (i.e., the "warping" of these space-times) reaches a point (the quantum gravity threshold) where the system must choose one state.
The system must then spontaneously and abruptly collapse to that one state.
This "self-collapse" results in particular "conformational states" that regulate neural processes. These conformational states can interact with neighboring states to represent, propagate and process information.
The proteins somehow "tune" the objective reduction which is thus self-organized, or "orchestrated".
In general, the collapse of the wave function
is what gives the laws of nature a non-algorithmic element.
Otherwise we would simply be machines and we would have no consciousness.
Therefore, "protoconscious" information is encoded in space-time geometry at the fundamental Planck scale and that a self-organizing Planck-scale process results in consciousness.
Penrose is stronger in his own backyard, when he describes objective reduction and comments on what has been known as the "Von Neumann measurement problem" of Quantum Theory.
The book is clearly divided in two parts,
The first part is a proof that traditional Physics is not adequate to explain consciousness. The second part uses Quantum Theory to draft a theory of consciousness.
Penrose starts his argument by stating that classical Physics is inadequate to explain consciousness.
Somehow this relates to Goedel's theorem, which puts a limit to what a Turing machine can do, a limit that does not apply to the human mind;
Consciousness must be a quantum phenomenon because neurons are too big to account for consciousness. Inside neurons there is a cytoskeleton, the structure that holds cells together, whose microtubules (hollow protein cylinders 25-nanometers in diameter)
control the function of synapses.
Penrose believes that consciousness is a manifestation of the quantum cytoskeletal state and its interplay between quantum and classical levels of activity.
Subjective reduction is what happens
when an observer measures a quantity in a quantum system:
the system is not in any specific state ,the system is in a "superposition" of possible states.
until it is observed,
the observation causes the system to reduce (or "collapse")
to a specific state.
This is the only reduction known to traditional Quantum Theory.
Objective reduction is a Penrose discovery, part of his attempt at unifying Relativity Theory and Quantum Theory.
Super positioned states each have their own spacetime geometries.
Under special circumstances, which microtubules are suitable for, the separation of spacetime geometry of the superpositioned states (i.e., the "warping" of these space-times) reaches a point (the quantum gravity threshold) where the system must choose one state.
The system must then spontaneously and abruptly collapse to that one state.
This "self-collapse" results in particular "conformational states" that regulate neural processes. These conformational states can interact with neighboring states to represent, propagate and process information.
The proteins somehow "tune" the objective reduction which is thus self-organized, or "orchestrated".
In general, the collapse of the wave function
is what gives the laws of nature a non-algorithmic element.
Otherwise we would simply be machines and we would have no consciousness.
Therefore, "protoconscious" information is encoded in space-time geometry at the fundamental Planck scale and that a self-organizing Planck-scale process results in consciousness.
Penrose is stronger in his own backyard, when he describes objective reduction and comments on what has been known as the "Von Neumann measurement problem" of Quantum Theory.
February 26, 2018
The origins of consciousness are either an elusive mystery or something as painfully obvious as gravity. For many years, I didn't really even know there was an issue of consciousness and just assumed it was a natural consequence of the brain (generator of the soul in my theistic view but still intrinsically linked). In fact, there's a huge feud going on among scientists and philosophers over why a bunch of electrical meat generates "you" and "me." There's a number of theories ranging from the insane ("panpsychism") to the boringly mundane ("neurons") to the also insane but materialist ("there's no such thing as consciousness").
Sir Roger Penrose, one of the smartest men alive, teams up with Doctor Stuart Hammeroff to offer their own version that consciousness is a product of quantum physics ("qubits" or quantum information) interacting with the microtubbles in the brain. If that sounds like Greek to you and you're not Greek, it basically means consciousness exists as a product of physics rather than biology. In more esoteric terms, it means consciousness is the result of quantum collapse between information states. Schrodinger's Cat of the cat being both dead and alive is the basis for consciousness as our thoughts are the physical representation of those things coalescing into "yes, the cat is frigging dead."
This is a theory which absolutely INFURIATES all manner of neurologists and physicists who believe it is ludicrous. Given the sheer volume of "quantum woo" (a.k.a pseudoscience), this is a reasonable fear but for the fact Penrose is one of the smartest men on the planet and Stuart Hammeroff's claims have repeatedly ended up being validated. Unfortunately, Hammeroff's claims have been somewhat tainted by his association with a bunch of very questionable figures (*cough* Deepak Chopra *cough*).
The biggest consequence of this theory is that it does have one big huge effect on the immediate future of technology: artificial intelligence. If Penrose's theory is correct, basically, computational A.I. is impossible for humans to create. It is a biological process which is related to the celestial geometry of the universe. No matter how we program our NPCs, they'll never be able to be conscious. That's another reason the theory really ticks a lot of people off.
The other flaw is the fact this book isn't exactly written for laymen. I know a good deal of physics for an amateur and required a couple of other scientists to understand everything which was being said. Penrose basically assumes his readers are familiar with not only quantum physics, his previous work, computation, but also problems of free will.
Personally, I'm inclined to believe Orch-Or theory is the source of human consciousness. In effect, "imagination" is the real multiverse since alternate realities last only as long as they're thought of. The biggest flaw of this book, though, is a lot of the collaborating evidence for its truth came out through studies conducted after it was written.
Many people still dispute this theory but no one has been able to put up a better one, IMHO.
Sir Roger Penrose, one of the smartest men alive, teams up with Doctor Stuart Hammeroff to offer their own version that consciousness is a product of quantum physics ("qubits" or quantum information) interacting with the microtubbles in the brain. If that sounds like Greek to you and you're not Greek, it basically means consciousness exists as a product of physics rather than biology. In more esoteric terms, it means consciousness is the result of quantum collapse between information states. Schrodinger's Cat of the cat being both dead and alive is the basis for consciousness as our thoughts are the physical representation of those things coalescing into "yes, the cat is frigging dead."
This is a theory which absolutely INFURIATES all manner of neurologists and physicists who believe it is ludicrous. Given the sheer volume of "quantum woo" (a.k.a pseudoscience), this is a reasonable fear but for the fact Penrose is one of the smartest men on the planet and Stuart Hammeroff's claims have repeatedly ended up being validated. Unfortunately, Hammeroff's claims have been somewhat tainted by his association with a bunch of very questionable figures (*cough* Deepak Chopra *cough*).
The biggest consequence of this theory is that it does have one big huge effect on the immediate future of technology: artificial intelligence. If Penrose's theory is correct, basically, computational A.I. is impossible for humans to create. It is a biological process which is related to the celestial geometry of the universe. No matter how we program our NPCs, they'll never be able to be conscious. That's another reason the theory really ticks a lot of people off.
The other flaw is the fact this book isn't exactly written for laymen. I know a good deal of physics for an amateur and required a couple of other scientists to understand everything which was being said. Penrose basically assumes his readers are familiar with not only quantum physics, his previous work, computation, but also problems of free will.
Personally, I'm inclined to believe Orch-Or theory is the source of human consciousness. In effect, "imagination" is the real multiverse since alternate realities last only as long as they're thought of. The biggest flaw of this book, though, is a lot of the collaborating evidence for its truth came out through studies conducted after it was written.
Many people still dispute this theory but no one has been able to put up a better one, IMHO.
January 24, 2023
this book took me months to finish because i was stupid enough to do the emperors new mind rereading not long before i started this one and as the author notes, there is great overlap. i, being as stuck in my ways as i am, couldnt relax into skipping the parts that are "the same" which meant that i was mindnumbingly bored for the first part- so i put it away. but i needed to get to the new parts for my thesis so i picked it up again last week and pushed through until the fun started. and it was worth it.
it is definitely much better than enm if youre interested in the mind itself. enm is way more technical and detailed and you wont find as much talk about some otherwise very cool topics (recursive sets, curvatures, phase space, and neuroscientific quirks) but it is structured more comprehensibly; to explain: enm is a field guide to physics and math with a few rather undefined thoughts about the nature of the mind that spring up at the start and the end, while shadows is more of a direct tour of cause-effect (or argument-conclusion) for penroses (still cursory, tbh) theory of the mind.
despite sir rogers best efforts of keeping the scope of the topic managable, there are still chapters that make it hard to see the forest despite the trees. but this is, for the most part, still more due to the nature of the topic (breadth, interconnectedness, complexity) and the shortcomings of the reader than the presentation itself. theres loads of examples and illustrations to drive the points home too. albeit sometimes the examples are still more confusing than probably ought be - the dodecahedron part, omg...
one can really see that dr. hameroff put in significant work to collaborate with the sir roger, because not only is there extensive talk about microtubules but also clathrins, ordered water, bose-einstein condensates, anaesthetics and all of the upsides and doubts of it all. its very nice (and reassuring) to see that they considered so many things that ive come across in research up to now ("humble" brag?). objective reduction is also developed and explained in much greater detail for which we are all thankful, i think. amazing what five years of thought can do!
i honestly believe that the times review "one of the most important works of the second half of the twetieth century" will only prove to be more indisputable in the future. didnt even bother earmarking this one cause there are little stars (in pencil) on the sides of almost every page. now all i gotta do is write the damn thing.
bit of a blog this review innit? till next time
it is definitely much better than enm if youre interested in the mind itself. enm is way more technical and detailed and you wont find as much talk about some otherwise very cool topics (recursive sets, curvatures, phase space, and neuroscientific quirks) but it is structured more comprehensibly; to explain: enm is a field guide to physics and math with a few rather undefined thoughts about the nature of the mind that spring up at the start and the end, while shadows is more of a direct tour of cause-effect (or argument-conclusion) for penroses (still cursory, tbh) theory of the mind.
despite sir rogers best efforts of keeping the scope of the topic managable, there are still chapters that make it hard to see the forest despite the trees. but this is, for the most part, still more due to the nature of the topic (breadth, interconnectedness, complexity) and the shortcomings of the reader than the presentation itself. theres loads of examples and illustrations to drive the points home too. albeit sometimes the examples are still more confusing than probably ought be - the dodecahedron part, omg...
one can really see that dr. hameroff put in significant work to collaborate with the sir roger, because not only is there extensive talk about microtubules but also clathrins, ordered water, bose-einstein condensates, anaesthetics and all of the upsides and doubts of it all. its very nice (and reassuring) to see that they considered so many things that ive come across in research up to now ("humble" brag?). objective reduction is also developed and explained in much greater detail for which we are all thankful, i think. amazing what five years of thought can do!
i honestly believe that the times review "one of the most important works of the second half of the twetieth century" will only prove to be more indisputable in the future. didnt even bother earmarking this one cause there are little stars (in pencil) on the sides of almost every page. now all i gotta do is write the damn thing.
bit of a blog this review innit? till next time
August 31, 2023
Shadows of the Mind: A Search for the Missing Science of Consciousness is Roger Penrose’s second book on human consciousness. It was published in 1994, five years after The Emperor’s New Mind (ENM). This review continues my review of both books since they cover many of the same topics.
As I related in my earlier review of ENM, I had become fascinated by the possibility of artificial intelligence in the 1980s due to my responsibility to create an investment accounting system for large insurance companies. Penrose’s two books challenged my expectations, and I read them carefully. They are not easy to summarize, but I will attempt to relate how they changed my thinking about the nature of life and the nature of the universe. It has been a transformational experience, but it did require significant time to educate myself about quantum theory. (QT).
ENM primarily presents the argument that human consciousness has abilities that transcend AI. It points toward a theory of consciousness and sets the groundwork for it but does not complete it. Shadows completes the outline of his foundational hypothesis. By proposing Objective Reduction for QT, ENM sets the stage for allowing discussion of Quantum Theory’s role in human consciousness.
Shadows of the Mind provides a compelling argument for why QT is likely involved in the science of consciousness. Therefore, Penrose includes an extensive description of the mysteries of QT in the book. He also recapitulates and strengthens his argument about Gödel’s Incompleteness Theorem, which precludes “strong AI.” He argues that human intelligence must include non-determinative processes because a determinative process would be constrained by Gödel’s Incompleteness Theorem. QT, when enhanced by Objective Reduction, is such a non-determinative process.
The non-determinative process must also provide an adaptive advantage and evolutionary success. Randomness is non-determinative but cannot contribute to evolutionary advantage. Nor can randomness provide a basis for consistent and coherent thinking about the universe.
The most important mystery of QT to understand is called entanglement. Quantum particles are entangled because physical quantities must be conserved. Energy, momentum, charge, and spin are all conserved quantities. We have not observed any violations of the conservation laws beyond what is allowed by the Heisenberg uncertainty principle.
The nature of entanglement evolved from discussions and debates between Albert Einstein and Neils Bohr in the 1930s. Because the state of a quantum particle cannot be determined until a measurement occurs, conservation laws would require an entangled particle to immediately transition to a known state based on the observation of its entangled partner. If the quantum states were not absolute but determined by measurement, as Bohr believed, this would require instantaneous synchronization between the two particles. Such immediate action would violate Einstein’s belief in absolute limits on the speed of light if the two particles were sufficiently separated in space.
Einstein proposed a simple thought experiment to determine if Bohr was correct. He and two others proposed the Einstein–Podolsky–Rosen (EPR) thought experiment to show that quantum theory was incomplete. Einstein argued that there must be a property, as yet undiscovered, of quantum systems that predetermined the final states of the two particles. In other words, there was no measurement problem because the quantum states were predetermined. If that were true, then observation or measurement has nothing to do with the outcome of experiments.
It wasn’t until 1964 that John Stewart Bell proposed an experiment allowing a real test of EPR. His proposal required measurement accuracy that wasn’t achieved until the early 1980s. The outcome of the Alain Aspect experiment in 1982 and subsequent improvements confirmed that Bohr was right and Einstein was wrong. Instantaneous synchronization of two separated quantum particles was indeed occurring. However, with a nod to Einstein, there is no way to use this phenomenon to transmit other messages faster than light. Only quantum state information can be transmitted faster than light. Two different terms are “non-local transmission” and “transmission backward in time.” Alain Aspect and two others were awarded the Nobel Prize in Physics for this work in 2022. John Bell would have certainly been included had he not died in 1990 at the relatively young age of 62.
This remarkable outcome is equivalent to two persons who cannot communicate with each other and simultaneously flip coins, which always turn out the same: both heads or tails! It does not matter whether the two people are at opposite ends of a room, opposite ends of the earth, or opposite ends of the universe.
The implications of this experiment to disprove the EPR hypothesis are controversial because they lead to speculation about the nature of the universe. Is “non-locality” a fundamental property of the universe? Is causality violated? Is time reversible? Some physicists are concerned that any notion of “spooky action at a distance” is anathema and will lead to irrational ideas and superstitions. One consequence of these developments is difficulty maintaining rational discussion.
Recently, there has been a trend toward panpsychism or even hylozoism. This trend gives some credibility to the opinion that all matter is conscious (panpsychism) or living (hylozoism). Some have ventured the idea that “the mechanism demands a mysticism.” It is difficult to escape these explorations since we have apparently reached the end of the road for the centuries-long strategy of reductionism that has led us straight back to our consciousness. Physicists are reluctant for good reasons to encourage these discussions.
Yet, some of the best scientific minds have ventured into territory where scientific data is not the only determining factor. I applaud their willingness to accept the risk because, almost always, there is professional criticism as they write and speak about areas outside of science.
Roger Penrose used his analysis of Gödel Incompleteness to argue against “strong AI” and for his theory of quantum gravity. He openly proclaims a Platonic worldview inspired by mathematics and interprets the mathematics of quantum theory as representing reality. So, perhaps for Penrose, Quantum Theory is not incomplete or can be completed by a proper role for quantum gravity, which he proposes.
Penrose argues that the wave nature of particles undergoes an objective transition due to the action of gravity and not because of observation. He has proposed tests that might one day confirm this. I am not convinced that his proposals will offer conclusive evidence. Yet, his arguments may win out because of their simplicity and explanatory power.
But Penrose goes further than proposing Quantum Gravity. He and anesthesiologist Stuart Hameroff argue that tiny molecular structures in cells called microtubules participate in quantum computations that control the molecular states of the component tubulin molecules. Brain neurons have a high density of microtubules. They assert that the molecular conformations of these molecules undergird consciousness. Tubulin molecular structures would then be the neural correlates of consciousness. He also extends the concept of OR (Objective Reduction) to Orchestrated OR, allowing the brain/mind to arrive at a conscious moment. A conscious moment provides a basis for answering the “hard problem” of consciousness.
To illustrate how Penrose has put his considerable reputation at risk by writing and speaking about the role of physics in human consciousness, here is a description of the Penrose-Hameroff hypothesis from Quantum Enigma: Physics Encounters Consciousness:
This 2006 book by Bruce Rosenblum and Fred Kuttner presents the facts of quantum theory and its controversy. The book’s dedication is to John Stewart Bell, mentioned above:
One of the authors, Bruce Rosenblum, spent an afternoon with Albert Einstein as a graduate student studying QT. He tells the story of Einstein’s persistent questioning of quantum theory. Even late in life, Einstein had misgivings about the theory, believing it to be incomplete.
These narratives from scientific professionals lead me to observe that the quantum paradox is similar to the Gödel version of the liar’s paradox. Quantum theory is a formal system, not unlike Gödel’s mathematical system, that formulates a theorem that proclaims its own falsehood. In this case, through entanglement and measurement evidence, QT asserts that our view of space-time is incomplete or incorrect. Space-time is non-local. No hidden, undiscovered variable will allow a “realistic” interpretation of instantaneous action at a distance.
The resolution of the paradox is through human consciousness, discernment, judgment, and decision. In my case, I believe, as John Bell proffered, that QT points outside space-time to the power that constituted it. As a corollary, QT tells us something extraordinary about human consciousness: we can experience our awareness of paradox and sense where it might lead us. Here is my explanation for why human consciousness has this remarkable ability.
It begins with an observation that our minds are remarkably well adapted to order our thoughts and observations and to propose solutions to the perceived chaos in the world. In the language of mathematics and physics, this is called reduction of entropy. We structure the world, order our days, and try to bring meaning and order into our lives so that we might thrive and do well. While we can be fooled, we can also recognize and correct mistakes.
My next step is to note Stephen Hawking’s explanation for the forward arrow of time in A Brief History of Time, 1988. (See chapter 9, “The Arrow of Time.”) He suggests, but does not elaborate, that time appears to move forward because the universe began in an extremely ordered, low-entropy state. Our experience of time moves towards the future because entropy is constantly increasing. If the universe had started in a state of high entropy (disorder) and continually became more ordered, we would experience time moving backward. Broken coffee cups would suddenly leap up and reassemble themselves on the table.
Shadows of the Mind includes Penrose’s similar analysis of entropy and the arrow of time. In both books, Penrose calculates how unusual the low entropy at creation was. Penrose’s calculation shows that the low entropy had an almost impossible chance of being created by chance.
So the question arises: What ability does consciousness have that allows our minds to bring order into our world? The answer is as obvious as it is boggling: time must move backward to reduce entropy. The mind’s biological action must be able to reverse time on a limited scale. One can get a sense of this from anecdotal evidence of the sort offered by Michael Jordan on why he has superstar abilities:
How our minds do this is part of the mystery of consciousness. Roger Penrose has allowed for this possibility in the Penrose-Hameroff hypothesis. Penrose has stated that information from a quantum computation can pass backward through time. However, all of his statements are carefully couched in QT arguments. Here is one that is more direct than others: “Remarkably, there is even nothing against quantum information `traveling backward in time’; indeed, such curious behavior seems to be required, as we shall see.” (“Quantum computation, entanglement, and state reduction” appearing in Philosophical Transactions of the Royal Society of London A, August 15th 1998, volume 356, issue 1743, pages 1927-1939).
A backward-forward time loop provides a “present moment” to experience consciousness. Increasing entropy eventually wins out, and time does move forward. One could also take the view that this time loop provides for our sense that part of our being is immortal.
The search for experimental evidence is proceeding along two fronts. One is the search for confirmation from quantum gravity. This will require proof that OR does occur when the amount of gravitational energy necessary to reconcile the space-time separation in the wave function has reached a critical threshold. The other front is the search for biological confirmation of quantum computation in microtubules. Both approaches are being pursued.
Whatever the outcomes of the search for evidence, both books, The Emperor’s New Mind and Shadows of the Mind, by Roger Penrose, have stimulated my thinking about the nature of the universe and humankind.
As I related in my earlier review of ENM, I had become fascinated by the possibility of artificial intelligence in the 1980s due to my responsibility to create an investment accounting system for large insurance companies. Penrose’s two books challenged my expectations, and I read them carefully. They are not easy to summarize, but I will attempt to relate how they changed my thinking about the nature of life and the nature of the universe. It has been a transformational experience, but it did require significant time to educate myself about quantum theory. (QT).
ENM primarily presents the argument that human consciousness has abilities that transcend AI. It points toward a theory of consciousness and sets the groundwork for it but does not complete it. Shadows completes the outline of his foundational hypothesis. By proposing Objective Reduction for QT, ENM sets the stage for allowing discussion of Quantum Theory’s role in human consciousness.
Shadows of the Mind provides a compelling argument for why QT is likely involved in the science of consciousness. Therefore, Penrose includes an extensive description of the mysteries of QT in the book. He also recapitulates and strengthens his argument about Gödel’s Incompleteness Theorem, which precludes “strong AI.” He argues that human intelligence must include non-determinative processes because a determinative process would be constrained by Gödel’s Incompleteness Theorem. QT, when enhanced by Objective Reduction, is such a non-determinative process.
The non-determinative process must also provide an adaptive advantage and evolutionary success. Randomness is non-determinative but cannot contribute to evolutionary advantage. Nor can randomness provide a basis for consistent and coherent thinking about the universe.
The most important mystery of QT to understand is called entanglement. Quantum particles are entangled because physical quantities must be conserved. Energy, momentum, charge, and spin are all conserved quantities. We have not observed any violations of the conservation laws beyond what is allowed by the Heisenberg uncertainty principle.
The nature of entanglement evolved from discussions and debates between Albert Einstein and Neils Bohr in the 1930s. Because the state of a quantum particle cannot be determined until a measurement occurs, conservation laws would require an entangled particle to immediately transition to a known state based on the observation of its entangled partner. If the quantum states were not absolute but determined by measurement, as Bohr believed, this would require instantaneous synchronization between the two particles. Such immediate action would violate Einstein’s belief in absolute limits on the speed of light if the two particles were sufficiently separated in space.
Einstein proposed a simple thought experiment to determine if Bohr was correct. He and two others proposed the Einstein–Podolsky–Rosen (EPR) thought experiment to show that quantum theory was incomplete. Einstein argued that there must be a property, as yet undiscovered, of quantum systems that predetermined the final states of the two particles. In other words, there was no measurement problem because the quantum states were predetermined. If that were true, then observation or measurement has nothing to do with the outcome of experiments.
It wasn’t until 1964 that John Stewart Bell proposed an experiment allowing a real test of EPR. His proposal required measurement accuracy that wasn’t achieved until the early 1980s. The outcome of the Alain Aspect experiment in 1982 and subsequent improvements confirmed that Bohr was right and Einstein was wrong. Instantaneous synchronization of two separated quantum particles was indeed occurring. However, with a nod to Einstein, there is no way to use this phenomenon to transmit other messages faster than light. Only quantum state information can be transmitted faster than light. Two different terms are “non-local transmission” and “transmission backward in time.” Alain Aspect and two others were awarded the Nobel Prize in Physics for this work in 2022. John Bell would have certainly been included had he not died in 1990 at the relatively young age of 62.
This remarkable outcome is equivalent to two persons who cannot communicate with each other and simultaneously flip coins, which always turn out the same: both heads or tails! It does not matter whether the two people are at opposite ends of a room, opposite ends of the earth, or opposite ends of the universe.
The implications of this experiment to disprove the EPR hypothesis are controversial because they lead to speculation about the nature of the universe. Is “non-locality” a fundamental property of the universe? Is causality violated? Is time reversible? Some physicists are concerned that any notion of “spooky action at a distance” is anathema and will lead to irrational ideas and superstitions. One consequence of these developments is difficulty maintaining rational discussion.
Recently, there has been a trend toward panpsychism or even hylozoism. This trend gives some credibility to the opinion that all matter is conscious (panpsychism) or living (hylozoism). Some have ventured the idea that “the mechanism demands a mysticism.” It is difficult to escape these explorations since we have apparently reached the end of the road for the centuries-long strategy of reductionism that has led us straight back to our consciousness. Physicists are reluctant for good reasons to encourage these discussions.
Yet, some of the best scientific minds have ventured into territory where scientific data is not the only determining factor. I applaud their willingness to accept the risk because, almost always, there is professional criticism as they write and speak about areas outside of science.
Roger Penrose used his analysis of Gödel Incompleteness to argue against “strong AI” and for his theory of quantum gravity. He openly proclaims a Platonic worldview inspired by mathematics and interprets the mathematics of quantum theory as representing reality. So, perhaps for Penrose, Quantum Theory is not incomplete or can be completed by a proper role for quantum gravity, which he proposes.
Penrose argues that the wave nature of particles undergoes an objective transition due to the action of gravity and not because of observation. He has proposed tests that might one day confirm this. I am not convinced that his proposals will offer conclusive evidence. Yet, his arguments may win out because of their simplicity and explanatory power.
But Penrose goes further than proposing Quantum Gravity. He and anesthesiologist Stuart Hameroff argue that tiny molecular structures in cells called microtubules participate in quantum computations that control the molecular states of the component tubulin molecules. Brain neurons have a high density of microtubules. They assert that the molecular conformations of these molecules undergird consciousness. Tubulin molecular structures would then be the neural correlates of consciousness. He also extends the concept of OR (Objective Reduction) to Orchestrated OR, allowing the brain/mind to arrive at a conscious moment. A conscious moment provides a basis for answering the “hard problem” of consciousness.
To illustrate how Penrose has put his considerable reputation at risk by writing and speaking about the role of physics in human consciousness, here is a description of the Penrose-Hameroff hypothesis from Quantum Enigma: Physics Encounters Consciousness:
The three bases of the Penrose-Hameroff theory – noncomputability, the involvement of quantum gravity, and the role of tubulins – are each controversial. And the entire theory has been derided as having the explanatory power of “pixie dust in the synapses.” (p 190).
This 2006 book by Bruce Rosenblum and Fred Kuttner presents the facts of quantum theory and its controversy. The book’s dedication is to John Stewart Bell, mentioned above:
Suppose that when [a complete] formulation [of quantum theory] . . .is attempted, we find an unmovable finger obstinately pointing outside the subject, to the mind of the observer, to the Hindu scriptures, to God, or even only Gravitation? Would that not be very, very interesting?
One of the authors, Bruce Rosenblum, spent an afternoon with Albert Einstein as a graduate student studying QT. He tells the story of Einstein’s persistent questioning of quantum theory. Even late in life, Einstein had misgivings about the theory, believing it to be incomplete.
These narratives from scientific professionals lead me to observe that the quantum paradox is similar to the Gödel version of the liar’s paradox. Quantum theory is a formal system, not unlike Gödel’s mathematical system, that formulates a theorem that proclaims its own falsehood. In this case, through entanglement and measurement evidence, QT asserts that our view of space-time is incomplete or incorrect. Space-time is non-local. No hidden, undiscovered variable will allow a “realistic” interpretation of instantaneous action at a distance.
The resolution of the paradox is through human consciousness, discernment, judgment, and decision. In my case, I believe, as John Bell proffered, that QT points outside space-time to the power that constituted it. As a corollary, QT tells us something extraordinary about human consciousness: we can experience our awareness of paradox and sense where it might lead us. Here is my explanation for why human consciousness has this remarkable ability.
It begins with an observation that our minds are remarkably well adapted to order our thoughts and observations and to propose solutions to the perceived chaos in the world. In the language of mathematics and physics, this is called reduction of entropy. We structure the world, order our days, and try to bring meaning and order into our lives so that we might thrive and do well. While we can be fooled, we can also recognize and correct mistakes.
My next step is to note Stephen Hawking’s explanation for the forward arrow of time in A Brief History of Time, 1988. (See chapter 9, “The Arrow of Time.”) He suggests, but does not elaborate, that time appears to move forward because the universe began in an extremely ordered, low-entropy state. Our experience of time moves towards the future because entropy is constantly increasing. If the universe had started in a state of high entropy (disorder) and continually became more ordered, we would experience time moving backward. Broken coffee cups would suddenly leap up and reassemble themselves on the table.
Shadows of the Mind includes Penrose’s similar analysis of entropy and the arrow of time. In both books, Penrose calculates how unusual the low entropy at creation was. Penrose’s calculation shows that the low entropy had an almost impossible chance of being created by chance.
So the question arises: What ability does consciousness have that allows our minds to bring order into our world? The answer is as obvious as it is boggling: time must move backward to reduce entropy. The mind’s biological action must be able to reverse time on a limited scale. One can get a sense of this from anecdotal evidence of the sort offered by Michael Jordan on why he has superstar abilities:
Suddenly, all is quiet. The other nine players? They’re all moving in slow motion! I’m at normal speed! I know where everyone’s going even before they know themselves. The basket is huge, maybe six feet across! How can I miss? It’s like throwing a rock into a pond. (Michael Jordan’s Little Book of Selected Quotes, published by Amazon Digital Services LLC, 2021.)
How our minds do this is part of the mystery of consciousness. Roger Penrose has allowed for this possibility in the Penrose-Hameroff hypothesis. Penrose has stated that information from a quantum computation can pass backward through time. However, all of his statements are carefully couched in QT arguments. Here is one that is more direct than others: “Remarkably, there is even nothing against quantum information `traveling backward in time’; indeed, such curious behavior seems to be required, as we shall see.” (“Quantum computation, entanglement, and state reduction” appearing in Philosophical Transactions of the Royal Society of London A, August 15th 1998, volume 356, issue 1743, pages 1927-1939).
A backward-forward time loop provides a “present moment” to experience consciousness. Increasing entropy eventually wins out, and time does move forward. One could also take the view that this time loop provides for our sense that part of our being is immortal.
The search for experimental evidence is proceeding along two fronts. One is the search for confirmation from quantum gravity. This will require proof that OR does occur when the amount of gravitational energy necessary to reconcile the space-time separation in the wave function has reached a critical threshold. The other front is the search for biological confirmation of quantum computation in microtubules. Both approaches are being pursued.
Whatever the outcomes of the search for evidence, both books, The Emperor’s New Mind and Shadows of the Mind, by Roger Penrose, have stimulated my thinking about the nature of the universe and humankind.
February 11, 2023
(4.5/5)
The book is divided into two parts, in the first part he explains about 4 possibilities for robots to develop consciousness.
A) that the robot is aware
B) that the robot seems conscious but is not
C) consciousness is not computable
D) consciousness is outside the laws of physics.
In the first part, he shows us why consciousness is not computable through the unanswered problems of Turing machines and Godel's theorem. In the second part, he is in charge of demonstrating how consciousness can be non-computable, lying on quantum principles. And he tells us about the brain structure, the microtubules and the possibility that all of them are producing quantum coherence together... Quantum coherence is the state where the particles are not entangled (as in superconductivity) and the states "yes" and "not" are separated.
He tells us a little about how it is necessary to reform the theories of current quantum physics, so that they adapt to some non-linear theory of time, but perhaps circular. Where the future affects the past...
It ends with a beautiful dialogue about the three worlds (physical, perceptive and mental), and the role that consciousness plays in all of them.
In general the book is very good and easy to understand theoretically, however in some parts it becomes tedious due to the equations presented and the problems that are somewhat complex to imagine visually (such as the dodecahedron). Not counting that, I think the explanation is good and leads to interesting conclusions.
The book is divided into two parts, in the first part he explains about 4 possibilities for robots to develop consciousness.
A) that the robot is aware
B) that the robot seems conscious but is not
C) consciousness is not computable
D) consciousness is outside the laws of physics.
In the first part, he shows us why consciousness is not computable through the unanswered problems of Turing machines and Godel's theorem. In the second part, he is in charge of demonstrating how consciousness can be non-computable, lying on quantum principles. And he tells us about the brain structure, the microtubules and the possibility that all of them are producing quantum coherence together... Quantum coherence is the state where the particles are not entangled (as in superconductivity) and the states "yes" and "not" are separated.
He tells us a little about how it is necessary to reform the theories of current quantum physics, so that they adapt to some non-linear theory of time, but perhaps circular. Where the future affects the past...
It ends with a beautiful dialogue about the three worlds (physical, perceptive and mental), and the role that consciousness plays in all of them.
In general the book is very good and easy to understand theoretically, however in some parts it becomes tedious due to the equations presented and the problems that are somewhat complex to imagine visually (such as the dodecahedron). Not counting that, I think the explanation is good and leads to interesting conclusions.
May 29, 2015
The author's stand, that we need new physics to understand the science of consciousness, and that this new physics he believes required is quantum physics, seems more his personal intuition (read delusion if you like!) than rigorous scientific inference. Applying models of sub-atomic phenomena to comprehend biological or life processes separated by very many orders of magnitude is an unscientific stretch too far. Quantum uncertainty of sub-atomic particles or fields does not map, by any evidence or intuition, to decision uncertainty in organic neural networks. Likewise, wave-particle duality in sub-atomic entities can hardly be called equivalent to concepts relating to the mind and the brain.
October 7, 2025
Roger Penrose’s Shadows of the Mind is a dense, ambitious dive into consciousness, computation, and physics, which I tackled with curiosity and a healthy dose of skepticism. This happened to be the one Penrose book my library had-which I was curious about after rereading Jim Holt’s Why Does the World Exist-as to Penrose’s three worlds theory, mixing Popper’s three worlds theory with Platonism. Going in I wasn’t sold on Penrose’s core claim that the mind isn’t computational and relies on quantum effects, but I was open to his arguments. He’s no lightweight—his grasp is impressive, and he’s not some dualist or mystical mentalist. As a physicalist, he argues the mind is open to scientific inquiry, just not ultimately explainable through computational rules.
Chapter 1, “Consciousness and Computation,” pretty much sums up the book, and the rest gets sometimes too technical for me, but it’s worth working through if you’re into big questions about AI, consciousness, or mathematical limits.
Penrose defines computation Turing-style, an idealized algorithmic binary machine that’s deterministic despite chaos, covering top-down symbolic AI and bottom-up connectionist neural nets.
Penrose lays out four viewpoints:
A (strong AI, minds are computational),
B (weak AI, simulation only),
C (physical but non-computational, his stance), and
D (non-physical, non-computational).
He’s all in on C, suggesting it’s an open question whether a physical system can work non-computationally, maybe via quantum effects. I lean toward A, not just because I think it’s plausible but because it’s ethically safer—assuming AI could be conscious means we’d consider rights and responsibilities for machines, unlike C or D, which risk dismissing their sentience. B’s too agnostic, just sitting on the fence.
Penrose presents Searle’s Chinese Room to cast doubt on A, arguing a rule-following system can mimic intelligence without understanding (B). Fair point, but it only affects qualia—the passive “what it’s like” of consciousness—not intentionality, the active, goal-directed part. It targets functionalism, not type-identity theory, which I think fits A better. With type-identity, the experience of “red” isn’t caused by computation but is identical to a brain state. Penrose’s question—how do algorithms do “red”?—doesn’t faze me. If red is just matter or information arranged a certain way, no fancy non-computational process are needed. Penrose assumes, like Searle, that consciousness is “somewhere” in the brain, unlike Dennett’s view of it as a distributed “narrative center,” not tied to one spot. He points to the cerebellum’s 80,000 synaptic connections, saying functionalism should make it conscious, yet it handles unconscious tasks like motor control. I’m not sold—the cerebellum’s part of the brain’s whole system, working with the cortex to shape behavior. Consciousness isn’t just one region; it’s the integrated output.
The rest of part 1 gets heavy with Gödel’s incompleteness theorems, arguing math can’t be fully computational because some truths, like Diophantine equations or tiling problems, can’t be proven algorithmically (tied to the halting problem). It got too technical, but comes down to first principles. Gödel’s theorems were about the axiomatic foundations of math, not computation. Penrose claims our intuitive grasp of natural numbers (0, 1, 2, 3) proves non-computational awareness, but I think evolution can explain that, if not intentional design. Our brains could have evolved bottom-up, like neural nets, to grasp what’s relevant bluntly, not to prove all math like an idealized Turing machine. Moravec’s paradox backs this: humans excel at specific tasks like elementary numbers because of evolutionary selection, not to gain a non-computational edge.
Part 2 dives into physics, arguing it’s incomplete because it doesn’t account for consciousness. Penrose introduces Z mysteries (experimentally supported but weird, like the double-slit experiment’s wave-particle duality) and X mysteries (paradoxical and speculative inferences, like Schrödinger’s cat, with superpositions like alive-and-dead cats) to show quantum mechanics’ explanatory gaps, especially the measurement problem—why we get a single reality. He critiques the dominant Copenhagen’s view, which prioritizes wave function collapse (R) over its evolution (U), and Many Worlds (MWI), which prioritizes U with all outcomes in branching universes, making R secondary. Penrose rejects both, proposing orchestrated objective reduction (OR), where gravity-driven collapse in brain microtubules balances R and U deterministically, unlike the random collapses in GRW theory. OR needs large-scale quantum effects—nonlocality (entangled correlations across distances), parallelism (multiple states processed simultaneously), and counterfactuality (outcomes tied to unrealized events)—to affect classical brain structures. But these effects must be shielded from decoherence in the brain’s warm, noisy environment, possibly via microtubule structures, which feels like a stretch without solid evidence.
Penrose ties OR to his microtubule hypothesis, where quantum effects enable non-computational insights. I’m not convinced. My preferred view, decoherent histories/path integral formulation, explains quantum outcomes as consistent histories, with environmental decoherence suppressing interference to produce classical results without collapse or branching. This fits a computational, type-identity model where consciousness arises from physical (informational) brain states, no new physics needed.
The conclusion, which I borrowed the book for, reworks Popper’s three worlds—abstract math, physical, mental—with a Platonic spin. Penrose sees consciousness accessing a math realm non-computationally via quantum effects, linking the worlds cyclically. I lean toward moderate realism, Platonic or Aristotelian, where only mathematical entities instantiated in physical things (form-matter compounds or object structures) exist—no separate realm needed. Computation’s just a subset of math, limited by our formalization, not awareness. A simulated universe? Sure, but only a subset of math needs to be computable for physical reality.
Penrose’s rigor is top-notch, and his critique of functionalism is sharp, but I’m not convinced the brain can’t be simulated computationally, blending top-down and bottom-up processes. His Gödel argument overreaches, OR and microtubules feel speculative albeit engaging, and decoherent histories handles quantum weirdness without his proposed new physics while being compatible with computable physics. Shadows of the Mind is a provocative, brain-bending read. It didn’t change my mind, but it made me wrestle with big questions and develop my views further, and that’s worth the slog.
Chapter 1, “Consciousness and Computation,” pretty much sums up the book, and the rest gets sometimes too technical for me, but it’s worth working through if you’re into big questions about AI, consciousness, or mathematical limits.
Penrose defines computation Turing-style, an idealized algorithmic binary machine that’s deterministic despite chaos, covering top-down symbolic AI and bottom-up connectionist neural nets.
Penrose lays out four viewpoints:
A (strong AI, minds are computational),
B (weak AI, simulation only),
C (physical but non-computational, his stance), and
D (non-physical, non-computational).
He’s all in on C, suggesting it’s an open question whether a physical system can work non-computationally, maybe via quantum effects. I lean toward A, not just because I think it’s plausible but because it’s ethically safer—assuming AI could be conscious means we’d consider rights and responsibilities for machines, unlike C or D, which risk dismissing their sentience. B’s too agnostic, just sitting on the fence.
Penrose presents Searle’s Chinese Room to cast doubt on A, arguing a rule-following system can mimic intelligence without understanding (B). Fair point, but it only affects qualia—the passive “what it’s like” of consciousness—not intentionality, the active, goal-directed part. It targets functionalism, not type-identity theory, which I think fits A better. With type-identity, the experience of “red” isn’t caused by computation but is identical to a brain state. Penrose’s question—how do algorithms do “red”?—doesn’t faze me. If red is just matter or information arranged a certain way, no fancy non-computational process are needed. Penrose assumes, like Searle, that consciousness is “somewhere” in the brain, unlike Dennett’s view of it as a distributed “narrative center,” not tied to one spot. He points to the cerebellum’s 80,000 synaptic connections, saying functionalism should make it conscious, yet it handles unconscious tasks like motor control. I’m not sold—the cerebellum’s part of the brain’s whole system, working with the cortex to shape behavior. Consciousness isn’t just one region; it’s the integrated output.
The rest of part 1 gets heavy with Gödel’s incompleteness theorems, arguing math can’t be fully computational because some truths, like Diophantine equations or tiling problems, can’t be proven algorithmically (tied to the halting problem). It got too technical, but comes down to first principles. Gödel’s theorems were about the axiomatic foundations of math, not computation. Penrose claims our intuitive grasp of natural numbers (0, 1, 2, 3) proves non-computational awareness, but I think evolution can explain that, if not intentional design. Our brains could have evolved bottom-up, like neural nets, to grasp what’s relevant bluntly, not to prove all math like an idealized Turing machine. Moravec’s paradox backs this: humans excel at specific tasks like elementary numbers because of evolutionary selection, not to gain a non-computational edge.
Part 2 dives into physics, arguing it’s incomplete because it doesn’t account for consciousness. Penrose introduces Z mysteries (experimentally supported but weird, like the double-slit experiment’s wave-particle duality) and X mysteries (paradoxical and speculative inferences, like Schrödinger’s cat, with superpositions like alive-and-dead cats) to show quantum mechanics’ explanatory gaps, especially the measurement problem—why we get a single reality. He critiques the dominant Copenhagen’s view, which prioritizes wave function collapse (R) over its evolution (U), and Many Worlds (MWI), which prioritizes U with all outcomes in branching universes, making R secondary. Penrose rejects both, proposing orchestrated objective reduction (OR), where gravity-driven collapse in brain microtubules balances R and U deterministically, unlike the random collapses in GRW theory. OR needs large-scale quantum effects—nonlocality (entangled correlations across distances), parallelism (multiple states processed simultaneously), and counterfactuality (outcomes tied to unrealized events)—to affect classical brain structures. But these effects must be shielded from decoherence in the brain’s warm, noisy environment, possibly via microtubule structures, which feels like a stretch without solid evidence.
Penrose ties OR to his microtubule hypothesis, where quantum effects enable non-computational insights. I’m not convinced. My preferred view, decoherent histories/path integral formulation, explains quantum outcomes as consistent histories, with environmental decoherence suppressing interference to produce classical results without collapse or branching. This fits a computational, type-identity model where consciousness arises from physical (informational) brain states, no new physics needed.
The conclusion, which I borrowed the book for, reworks Popper’s three worlds—abstract math, physical, mental—with a Platonic spin. Penrose sees consciousness accessing a math realm non-computationally via quantum effects, linking the worlds cyclically. I lean toward moderate realism, Platonic or Aristotelian, where only mathematical entities instantiated in physical things (form-matter compounds or object structures) exist—no separate realm needed. Computation’s just a subset of math, limited by our formalization, not awareness. A simulated universe? Sure, but only a subset of math needs to be computable for physical reality.
Penrose’s rigor is top-notch, and his critique of functionalism is sharp, but I’m not convinced the brain can’t be simulated computationally, blending top-down and bottom-up processes. His Gödel argument overreaches, OR and microtubules feel speculative albeit engaging, and decoherent histories handles quantum weirdness without his proposed new physics while being compatible with computable physics. Shadows of the Mind is a provocative, brain-bending read. It didn’t change my mind, but it made me wrestle with big questions and develop my views further, and that’s worth the slog.
November 18, 2016
What can I say about a book which challenged my mathematical understanding and revealed the unseen aspects of my own brain's cytoskeletal structures? Was it the knowledge that there is a type of water in these structures which is considered a necessary element for cancelling the interference that would null the necessary conditions for quantum coherence to take effect? Or was it the mathematical proof showing that because there are mathematical statements of which we know to be absolutely true yet cannot prove, then it follows for us to conclude that a computer could never achieve consciousness (at least with the 1994 mathematical understanding available)? Trust me, Roger Penrose does it in a supremely much more elegant fashion than I could ever do it justice with in a GoodReads summary. So why 4 stars? Well, I'm not an expert at Lambda Calculus or many of the subjects that Roger Penrose expertly weaves in and out of, so it became supremely hard to follow at times. However, I broke through this barrier and was able to glean from it the nuggets that I could understand. I recommend anyone interested in these subjects to do the same.
March 16, 2026
Shadows of the Mind by Roger Penrose
The crux of the argument (now commonly known as the Penrose-Lucas argument) is presented in §2.5, by mathematical proof. Though controversial, it’s a tremendously beautiful idea based on (but potentially a misinterpretation of) Gödel’s incompleteness theorems and Turing’s proof for the undecidability of the halting problem.
In essence, the proof shows that for any algorithmic procedure for ascertaining truth, there will always be something that the (mathematician’s) mind knows (to be true), that the algorithm will be fundamentally unable to know. Assuming that the algorithm in question is knowably sound.
The process we humans employ to ascertain truth cannot, therefore, be merely algorithmic in nature. From which follows that there has to be a non-computational (or non-algorithmic) element to (mathematical) understanding, supporting Penrose’s eventual conclusion that understanding, awareness and consciousness involve non-computational physical action.
Meaning that these processes can never be simulated by computers.
This claim is stronger than it at first sight may suggest. It asserts that there will never be any computer or any algorithm of any kind or complexity, capable of exhibiting, simulating or replicating any of these characteristics of the mind. It's a fundamental, and insurmountable hurdle on the road to 'thinking' computers or Artificial General Intelligence. As such, the argument functions as a strong refutation of the Strong AI thesis.
It does not, however, claim that there can never be some mechanical device other than a computer capable of replicating these processes, as it is not unforeseeable that one might, at one point in the future, mechanically and entirely replicate the human brain for example.
The controversial nature of the idea is perhaps best illustrated by the hundred or so pages devoted to discussing possible refutations concerning technicalities and assumptions underlying this proof. Though more or less understandable these are about as exciting as one can imagine.
It differs from an idea posited by John Searle by way of his famous Chinese Room thought experiment. Searle has stated that he believes all physical action to be computational in nature, from which follows that a computer or algorithm should in principle be able to simulate any and all of the mind’s processes. The thought experiment implies it would, however, not acquire actual understanding or actual awareness in the process. As Penrose notes, this puts a disturbing notion forth: if an algorithm is capable of simulating the mind entirely without such things as awareness, understanding, feelings or any other intelligent processes, do these processes have no role at all in human behavior? It would mean consciousness has no effect on behavior at all. It would raise some questions about the nature of free will as well.
And how would we be able to tell? If some future algorithm is capable of perfectly replicating the human mind, what reason would I have to doubt its having conscious awareness? In effect, if it passes a proper Turing test, why should I have any more reason to doubt its consciousness over some colleague or friend of mine? Certainly I have no way of proving or knowing that some person I see walking on the street has their own conscious experience. For one, I could simply be dreaming.
So where Searle believes algorithms in principle capable of perfectly simulating ‘intelligent’ human behavior (albeit without acquiring understanding), Penrose disagrees: no algorithm can fully replicate the mind’s processes, for some processes require non-algorithmic physical action.
I personally lean towards Searle’s vision, despite its uncomfortable implications. It would restrict the search for genuine machine intelligence to discovering what physical action in (and unique to) the brain causes our consciousness, awareness, understanding etc. Penrose’s view requires non-computational physical action, which, given no known real-world examples and contrived theoretical ones, seems far-fetched to say the least. Then again, should we not look far ahead for the key to perhaps the most mysterious and alien phenomena in the universe?
In part 2 of the book Penrose goes on to posit a theory on where in the brain this non-computational physical action could take place.
This part, though interesting, reads as highly speculative, and 3 decades later Penrose’s “quantum consciousness” is apparently in dire need of any empirical proof to support it. Penrose is the first to note the tentative nature of his hypothesis.
Penrose is kind to the reader, providing a path through the book without involved mathematics and lengthy discussions of technicalities. This path includes the first chapter which lays the groundwork for the entire argument, and functions as the most interesting and thought-provoking discussion of machine intelligence I’ve ever read. Despite being written 2 years before Kasparov’s defeat at the hands of Deep Blue in 1996, very little in this discussion feels dated. This follows from the fact that Penrose ruminates on and argues from timeless mathematical and computational principles, not hardware or algorithmic specifics.
For most practical purposes the conclusions of this book matter little. It features no argument against a future computer or algorithm capable of replicating most of (intelligent) human behavior very closely. LLM’s today show how much of ‘intelligent’ behavior by programmers for instance can be competently replicated by admittedly highly complex algorithms. All this argument claims is that however complex these or other algorithms may get, they will never be able to replicate some of the mind’s processes, like understanding and awareness. It follows that one’s ability to make use of these is inversely proportional to the risk of losing one’s job to algorithms.
Overall an incredibly thought-provoking read which presents some truly extraordinary ideas, but requires attentive and patient reading.
The crux of the argument (now commonly known as the Penrose-Lucas argument) is presented in §2.5, by mathematical proof. Though controversial, it’s a tremendously beautiful idea based on (but potentially a misinterpretation of) Gödel’s incompleteness theorems and Turing’s proof for the undecidability of the halting problem.
In essence, the proof shows that for any algorithmic procedure for ascertaining truth, there will always be something that the (mathematician’s) mind knows (to be true), that the algorithm will be fundamentally unable to know. Assuming that the algorithm in question is knowably sound.
The process we humans employ to ascertain truth cannot, therefore, be merely algorithmic in nature. From which follows that there has to be a non-computational (or non-algorithmic) element to (mathematical) understanding, supporting Penrose’s eventual conclusion that understanding, awareness and consciousness involve non-computational physical action.
Meaning that these processes can never be simulated by computers.
This claim is stronger than it at first sight may suggest. It asserts that there will never be any computer or any algorithm of any kind or complexity, capable of exhibiting, simulating or replicating any of these characteristics of the mind. It's a fundamental, and insurmountable hurdle on the road to 'thinking' computers or Artificial General Intelligence. As such, the argument functions as a strong refutation of the Strong AI thesis.
It does not, however, claim that there can never be some mechanical device other than a computer capable of replicating these processes, as it is not unforeseeable that one might, at one point in the future, mechanically and entirely replicate the human brain for example.
The controversial nature of the idea is perhaps best illustrated by the hundred or so pages devoted to discussing possible refutations concerning technicalities and assumptions underlying this proof. Though more or less understandable these are about as exciting as one can imagine.
It differs from an idea posited by John Searle by way of his famous Chinese Room thought experiment. Searle has stated that he believes all physical action to be computational in nature, from which follows that a computer or algorithm should in principle be able to simulate any and all of the mind’s processes. The thought experiment implies it would, however, not acquire actual understanding or actual awareness in the process. As Penrose notes, this puts a disturbing notion forth: if an algorithm is capable of simulating the mind entirely without such things as awareness, understanding, feelings or any other intelligent processes, do these processes have no role at all in human behavior? It would mean consciousness has no effect on behavior at all. It would raise some questions about the nature of free will as well.
And how would we be able to tell? If some future algorithm is capable of perfectly replicating the human mind, what reason would I have to doubt its having conscious awareness? In effect, if it passes a proper Turing test, why should I have any more reason to doubt its consciousness over some colleague or friend of mine? Certainly I have no way of proving or knowing that some person I see walking on the street has their own conscious experience. For one, I could simply be dreaming.
So where Searle believes algorithms in principle capable of perfectly simulating ‘intelligent’ human behavior (albeit without acquiring understanding), Penrose disagrees: no algorithm can fully replicate the mind’s processes, for some processes require non-algorithmic physical action.
I personally lean towards Searle’s vision, despite its uncomfortable implications. It would restrict the search for genuine machine intelligence to discovering what physical action in (and unique to) the brain causes our consciousness, awareness, understanding etc. Penrose’s view requires non-computational physical action, which, given no known real-world examples and contrived theoretical ones, seems far-fetched to say the least. Then again, should we not look far ahead for the key to perhaps the most mysterious and alien phenomena in the universe?
In part 2 of the book Penrose goes on to posit a theory on where in the brain this non-computational physical action could take place.
This part, though interesting, reads as highly speculative, and 3 decades later Penrose’s “quantum consciousness” is apparently in dire need of any empirical proof to support it. Penrose is the first to note the tentative nature of his hypothesis.
Penrose is kind to the reader, providing a path through the book without involved mathematics and lengthy discussions of technicalities. This path includes the first chapter which lays the groundwork for the entire argument, and functions as the most interesting and thought-provoking discussion of machine intelligence I’ve ever read. Despite being written 2 years before Kasparov’s defeat at the hands of Deep Blue in 1996, very little in this discussion feels dated. This follows from the fact that Penrose ruminates on and argues from timeless mathematical and computational principles, not hardware or algorithmic specifics.
For most practical purposes the conclusions of this book matter little. It features no argument against a future computer or algorithm capable of replicating most of (intelligent) human behavior very closely. LLM’s today show how much of ‘intelligent’ behavior by programmers for instance can be competently replicated by admittedly highly complex algorithms. All this argument claims is that however complex these or other algorithms may get, they will never be able to replicate some of the mind’s processes, like understanding and awareness. It follows that one’s ability to make use of these is inversely proportional to the risk of losing one’s job to algorithms.
Overall an incredibly thought-provoking read which presents some truly extraordinary ideas, but requires attentive and patient reading.
June 2, 2007
The central argument is not as airtight as it should be, being written for a general readership and not for mathematicians, but I'm just in love with the idea of a mathematical proof that the human mind can't be algorithmic. I wonder if Penrose has published a proper version of the proof?
The second half of the book, in which he speculates on what kinds of computation or processes might be the underpinnings of the working of the mind is also fascinating though, again, I don't find his arguments necessarily persuasive. (For instance, he basically waves away the "many worlds" interpretation of quantum uncertainty because he simply doesn't like it.) He's not quite as good a writer for the non-specialist as Sagan or Feynman, but he's a bona fide genius and his speculations are well worth the trouble to read and understand.
The second half of the book, in which he speculates on what kinds of computation or processes might be the underpinnings of the working of the mind is also fascinating though, again, I don't find his arguments necessarily persuasive. (For instance, he basically waves away the "many worlds" interpretation of quantum uncertainty because he simply doesn't like it.) He's not quite as good a writer for the non-specialist as Sagan or Feynman, but he's a bona fide genius and his speculations are well worth the trouble to read and understand.
August 29, 2016
Para un público muy limitado.
Para empezar, no recomendaría leer este libro a nadie que no haya leído previamente "La nueva mente del emperador". Aquel libro finalizaba con una serie de conjeturas sobre el posible modo en que funciona el pensamiento. En este "Las sombras de la mente" se sigue prácticamente con un punto y seguido a aquellas especulaciones. Se intenta apoyan con más evidencias las líneas de pensamiento allí esbozadas y refutar los argumentos contrarios que le han ido planteando a Penrose. Acompañar al autor en este viaje es una gimnasia mental sugerente y estimulante. Sin embargo, requiere un esfuerzo muy elevado para seguir unas líneas de pensamiento que no dejan de ser meras intuiciones.
Para empezar, no recomendaría leer este libro a nadie que no haya leído previamente "La nueva mente del emperador". Aquel libro finalizaba con una serie de conjeturas sobre el posible modo en que funciona el pensamiento. En este "Las sombras de la mente" se sigue prácticamente con un punto y seguido a aquellas especulaciones. Se intenta apoyan con más evidencias las líneas de pensamiento allí esbozadas y refutar los argumentos contrarios que le han ido planteando a Penrose. Acompañar al autor en este viaje es una gimnasia mental sugerente y estimulante. Sin embargo, requiere un esfuerzo muy elevado para seguir unas líneas de pensamiento que no dejan de ser meras intuiciones.
June 10, 2021
The entire argument can be reduced to "I presume that biological minds didn't evolve a a time-out mechanism, hence they are not computational". Algorithms usually have a stop function and even if they didn't, they can possibly run forever, hence the entirety of the premise falls apart.
And it takes soooo loooong to get there. I mean - people that are not interested in the topic won't read it anyway and for people that are interested, there is no need to explain every detail through 20 pages.
And although I think that consciousness if fundamentally quantum effect - there is nothing surprising about that. Everything is quantum in essence. Also - we are close to quantum computation and that will basically close the circle.
Universe is computational. Minds are computational.
And it takes soooo loooong to get there. I mean - people that are not interested in the topic won't read it anyway and for people that are interested, there is no need to explain every detail through 20 pages.
And although I think that consciousness if fundamentally quantum effect - there is nothing surprising about that. Everything is quantum in essence. Also - we are close to quantum computation and that will basically close the circle.
Universe is computational. Minds are computational.
December 13, 2025
4.5⭐
Más allá de la validez (aún por determinar) de las teorías propuestas, el simple hecho de que Penrose sea capaz de aunar argumentos en favor de la no computabilidad de la consciencia (siguiendo la linea del teorema de Gödel-Turing) con estudios de biología celular y teorías de gravedad cuántica, sin olvidar en ningún momento el nexo, casi filosófico, con el concepto práctico de "realidad" (por ejemplo, en términos de nuestra percepción consciente de una evolución temporal), hace que este libro sea per se una maravilla.
PERO que encima haya sido capaz de hacerlo entendible (y accesible) para el resto de los mortales??!!!!
Vaya locura.
Más allá de la validez (aún por determinar) de las teorías propuestas, el simple hecho de que Penrose sea capaz de aunar argumentos en favor de la no computabilidad de la consciencia (siguiendo la linea del teorema de Gödel-Turing) con estudios de biología celular y teorías de gravedad cuántica, sin olvidar en ningún momento el nexo, casi filosófico, con el concepto práctico de "realidad" (por ejemplo, en términos de nuestra percepción consciente de una evolución temporal), hace que este libro sea per se una maravilla.
PERO que encima haya sido capaz de hacerlo entendible (y accesible) para el resto de los mortales??!!!!
Vaya locura.
November 19, 2019
I probably would have given Penrose' book a 5-Star review were it not for the fact that a good third of the book was WAY over my head due to the heavy mathematics involved. However, I did grasp the basic concepts and arguments of the book, so 4-Stars will be OK.
Warning, though... this book has some heavy math in it. You can skim most of that and still understand what this man is trying to get across, though, so don't let this warning scare you off.
Warning, though... this book has some heavy math in it. You can skim most of that and still understand what this man is trying to get across, though, so don't let this warning scare you off.
October 13, 2023
The book took a lot of effort, but was worth it. Having read Road to Reality and Cycles of Time first, I can appreciate how this book sparked Penrose to go more in depth on the underlying mathematics, particularly of quantum mechanics. This book is not heavy in mathematical expressions, but still provided enough for me to follow his arguments, particularly on Gödel’s / Turing’s application to non-computability.
The analysis of microtubules is fascinating and promising. I can appreciate the function of classical neurophysiology from a new perspective. Rather than being the generator of conscious awareness, they are secondary to this process, for it is the magnetic field generated by their long axons (acting like wires) which interacts at a quantum level with the single electron in a tubulin protein, collectively making up a continuous entangled field of boson-electron superpositions that form a sort of hologram of the net activity of all neurons. Penrose makes an interesting argument for the difference between the cerebellum (with short axons, and where most activity is “unconscious”) and the cerebrum, associated with most conscious activity, with its long axons running to the opposite side of the brain, which further reinforces this image of axons functioning like the coils of wire that induce a magnetic field. A magnetic field being created by photons, we can imagine these photons interacting in the lumens of a microtubule, wherein columns of tubulin proteins shift configuration based on the quantum state of one electron. Given Penrose’s lucid description of how quantum superposition states exist as linear vector-like combinations of complex-number-weighted units, it is not difficult to see how counterfactual quantum states of entangled photons (from axon generated magnetic fields) with the electron in tubulin proteins can give rise to non-computation processes — namely, the kind which can evaluate the truth statement YES and NO when measured, which is necessary to describe the feats of human thinking which cannot be simulated by any means of computation.
Penrose lays the foundation for something deeper as well, and this lingers as I move on from this book. Microtubules are not unique to human neurons. They are contained in every cell of the body. Furthermore, they are contained in every Eukaryotic cell. Penrose shows how it could be possible that indeed, early forms of what would evolve into conscious awareness might have shaped organism decisions well before there were brains. What came together for me was something quite analogous to the way in which the mitochondria, critical to cellular energy, was originally a parasite that invaded, and soon was incorporated in as fundamental to the human being. Could the microtubule, a structure evolving in early cell architecture, and the true mediator of conscious awareness, have similarly acted like a parasite within Eurkayotic cells — now fundamental to what makes the human being, and all sentient beings, conscious? Without which our brains would merely be Turing machines generating meaningless electrical signals?
Perhaps most profound in this wasn’t just the new outlook on the evolutionary roots of conscious awareness, but the application of the quantum entanglement field concept beyond just the neurons of the brain. If indeed the individual human conscious awareness of a particular brain takes on the form of a continuous, holographic quantum field — a bit like all activity projected onto a movie screen — then where does the boundary stop? Is this “movie screen” limited to only the magnetic field of axon-generated photons, or are there subtler levels? Might other cells in the body participate in this field? Would this explain deeper brain-body awareness? Even further, would there be, on subtler levels (varying with the reduced magnetic field strength), extensions of this field to include entanglements with other systems, such as two humans in close proximity? A meditator in a field in a deep meditation wherein there is an expanded sense of body to include nearby animals, trees, and living things?
A good book doesn’t just leave you with facts. For me a sign of a great book is the questions I take away, and being sent on a quest for more. Penrose has accomplished this for me. Even if he is challenged by many who are quick to dismiss the possibility of quantum effects (but of course, most of these arguments are based on assuming superconductivity is not possible at the warm temperatures of the brain, and even at the time of writing Penrose pointed out some experiments had come quite close), Penrose at least dares to open a discussion on a topic that deserves scientific treatment the same way light, space, time, and energy do. What would that science look like? In my mind, that science will take us closer to the foundations of what reality actually is, and clarity on how the Platonic, mental, and physical worlds interrelate.
I hope Penrose will write on this topic again, particularly at this stage in his life where he has not published a book since 2007 with his Road to Reality. What has he discovered and come up with since putting this book forward in 1994, some 30 years ago? Whatever this might be, it is clear Penrose draws on a lifetime of some of the most sophisticated thought and understanding of the math and physics that define our world, and he is worth listening to.
The analysis of microtubules is fascinating and promising. I can appreciate the function of classical neurophysiology from a new perspective. Rather than being the generator of conscious awareness, they are secondary to this process, for it is the magnetic field generated by their long axons (acting like wires) which interacts at a quantum level with the single electron in a tubulin protein, collectively making up a continuous entangled field of boson-electron superpositions that form a sort of hologram of the net activity of all neurons. Penrose makes an interesting argument for the difference between the cerebellum (with short axons, and where most activity is “unconscious”) and the cerebrum, associated with most conscious activity, with its long axons running to the opposite side of the brain, which further reinforces this image of axons functioning like the coils of wire that induce a magnetic field. A magnetic field being created by photons, we can imagine these photons interacting in the lumens of a microtubule, wherein columns of tubulin proteins shift configuration based on the quantum state of one electron. Given Penrose’s lucid description of how quantum superposition states exist as linear vector-like combinations of complex-number-weighted units, it is not difficult to see how counterfactual quantum states of entangled photons (from axon generated magnetic fields) with the electron in tubulin proteins can give rise to non-computation processes — namely, the kind which can evaluate the truth statement YES and NO when measured, which is necessary to describe the feats of human thinking which cannot be simulated by any means of computation.
Penrose lays the foundation for something deeper as well, and this lingers as I move on from this book. Microtubules are not unique to human neurons. They are contained in every cell of the body. Furthermore, they are contained in every Eukaryotic cell. Penrose shows how it could be possible that indeed, early forms of what would evolve into conscious awareness might have shaped organism decisions well before there were brains. What came together for me was something quite analogous to the way in which the mitochondria, critical to cellular energy, was originally a parasite that invaded, and soon was incorporated in as fundamental to the human being. Could the microtubule, a structure evolving in early cell architecture, and the true mediator of conscious awareness, have similarly acted like a parasite within Eurkayotic cells — now fundamental to what makes the human being, and all sentient beings, conscious? Without which our brains would merely be Turing machines generating meaningless electrical signals?
Perhaps most profound in this wasn’t just the new outlook on the evolutionary roots of conscious awareness, but the application of the quantum entanglement field concept beyond just the neurons of the brain. If indeed the individual human conscious awareness of a particular brain takes on the form of a continuous, holographic quantum field — a bit like all activity projected onto a movie screen — then where does the boundary stop? Is this “movie screen” limited to only the magnetic field of axon-generated photons, or are there subtler levels? Might other cells in the body participate in this field? Would this explain deeper brain-body awareness? Even further, would there be, on subtler levels (varying with the reduced magnetic field strength), extensions of this field to include entanglements with other systems, such as two humans in close proximity? A meditator in a field in a deep meditation wherein there is an expanded sense of body to include nearby animals, trees, and living things?
A good book doesn’t just leave you with facts. For me a sign of a great book is the questions I take away, and being sent on a quest for more. Penrose has accomplished this for me. Even if he is challenged by many who are quick to dismiss the possibility of quantum effects (but of course, most of these arguments are based on assuming superconductivity is not possible at the warm temperatures of the brain, and even at the time of writing Penrose pointed out some experiments had come quite close), Penrose at least dares to open a discussion on a topic that deserves scientific treatment the same way light, space, time, and energy do. What would that science look like? In my mind, that science will take us closer to the foundations of what reality actually is, and clarity on how the Platonic, mental, and physical worlds interrelate.
I hope Penrose will write on this topic again, particularly at this stage in his life where he has not published a book since 2007 with his Road to Reality. What has he discovered and come up with since putting this book forward in 1994, some 30 years ago? Whatever this might be, it is clear Penrose draws on a lifetime of some of the most sophisticated thought and understanding of the math and physics that define our world, and he is worth listening to.
January 26, 2022
Very difficult to follow
September 12, 2025
One thing Roger Penrose can't be accused of is dumbing down for his audience. Shadows is a dense read, which doesn't shy away from mathematics and concepts tough to grasp. Don't try to read it quickly.
The basic thesis is that (mathematical) understanding, and by extension consciousness, is fundamentally not computable, and that therefore a non-computable mechanism needs to be invoked to explain it. Penrose bases his argument on a synthesis of Godel's incompleteness theorem and Turing's work on computable numbers and the decision problem, and defends it exhaustively against a long list of potential objections. (At the risk of over-simplifying: there are mathematical statements which cannot be formally proven to be true, but which can nevertheless be apprehended as being true. That apprehension is therefore not in itself computable).
He then proposes that the most likely candidate for this non-computable mechanism is whatever it is that causes a quantum state vector to 'collapse' into a classical state. (A characteristic of quantum mechanics being that a system can be in an indeterminate superposition of possible states, but collapses into a single, unambiguous state when a measurement is made.)
Penrose sets out some intriguing ideas that would bring general relativity into the picture to explain this process (a superposition of mass positions entangled with the environment that leads to a sufficiently high difference in gravitational energy between the superposed states). He also draws attention suggestively to David Deutsch's observation that a quantum theory of gravity would have to include closed timelike worldlines in a superposition, allowing for at least the possibility that a Turing machine could access its own output in its past. He admits that all this is essentially speculation, but maintains that whatever the mechanism proves to be, it would be non-computable and therefore a potential element in conscious experience.
Finally, he identifies possible macroscopic quantum coherence in the neural cytoskeleton as a candidate for the translation of this mechanism to actual subjective experience. This isn't something that's (yet) been observed, but whether or not you completely buy into what is essentially speculation, there's some very interesting material here about the properties of the cytoskeleton itself (which, among other things, should give proponents of 'consciousness uploading' pause for thought). There's more to electrical brain activity than just neurons.
Ultimately though, Shadows peters out somewhat, in the absence of a clearly articulated explanation of consciousness as a process (whether speculative or not). Penrose doesn't really try to say how this mass coherence might cause consciousness, just because state vector reduction is not computable.
I'm glad that I ploughed through it, but I'm left wondering what the book is for. I'm not sure that a work of popular science is the obvious channel for advancing new hypotheses that are meant to be taken seriously.
The basic thesis is that (mathematical) understanding, and by extension consciousness, is fundamentally not computable, and that therefore a non-computable mechanism needs to be invoked to explain it. Penrose bases his argument on a synthesis of Godel's incompleteness theorem and Turing's work on computable numbers and the decision problem, and defends it exhaustively against a long list of potential objections. (At the risk of over-simplifying: there are mathematical statements which cannot be formally proven to be true, but which can nevertheless be apprehended as being true. That apprehension is therefore not in itself computable).
He then proposes that the most likely candidate for this non-computable mechanism is whatever it is that causes a quantum state vector to 'collapse' into a classical state. (A characteristic of quantum mechanics being that a system can be in an indeterminate superposition of possible states, but collapses into a single, unambiguous state when a measurement is made.)
Penrose sets out some intriguing ideas that would bring general relativity into the picture to explain this process (a superposition of mass positions entangled with the environment that leads to a sufficiently high difference in gravitational energy between the superposed states). He also draws attention suggestively to David Deutsch's observation that a quantum theory of gravity would have to include closed timelike worldlines in a superposition, allowing for at least the possibility that a Turing machine could access its own output in its past. He admits that all this is essentially speculation, but maintains that whatever the mechanism proves to be, it would be non-computable and therefore a potential element in conscious experience.
Finally, he identifies possible macroscopic quantum coherence in the neural cytoskeleton as a candidate for the translation of this mechanism to actual subjective experience. This isn't something that's (yet) been observed, but whether or not you completely buy into what is essentially speculation, there's some very interesting material here about the properties of the cytoskeleton itself (which, among other things, should give proponents of 'consciousness uploading' pause for thought). There's more to electrical brain activity than just neurons.
Ultimately though, Shadows peters out somewhat, in the absence of a clearly articulated explanation of consciousness as a process (whether speculative or not). Penrose doesn't really try to say how this mass coherence might cause consciousness, just because state vector reduction is not computable.
I'm glad that I ploughed through it, but I'm left wondering what the book is for. I'm not sure that a work of popular science is the obvious channel for advancing new hypotheses that are meant to be taken seriously.
March 13, 2021
Да четеш книга написана от Роджър Пенроуз е изключително преживяване. Представете си сложността и абстрактността на квантовата теория. Представихте ли си го? Е, сега си представете, че човек, който е в състояние да вникне в детайли в цялата математика на комплексния анализ (която съпътства квантовата теория) и в цялата математика на тензорното смятане (която съпътства теорията на относителността) и дори лично е развил някои от тези математически дялове, ви обяснява какво го смущава в квантовата теория. Защото точно това се случва във втората част на книгата. Както казах - изключително преживяване.
Започнах с втората част, защото там е разковничето, което Роджър Пенроуз счита, че ще ни открехне вратата към един въпрос, който касае цялата книга - въпросът за това що е то съзнание и къде точно се случва. Първата част обаче е не по-малко вълнуваща. В нея се поставя въпросът, който днес е на дневен ред - изчислимо ли е осъзнаването. С други думи доколко един хипотетичен компютър (например много бърз и с много памет) би могъл на осъзнае нещо. За тази цел Роджър Пенроуз стъпва на теоремата на Гьодел и разглежда 4 основни хипотези, наречени А,Б,В,Г. Според хипотеза А, съзнанието е изчислимо. Според хипотеза Б, съзнанието не е изчислимо, но не съществува начин да бъде отличено от достатъчно сложен алгоритъм. Според хипотеза В, съзнанието не е изчислимо, но може да бъде научно изследвано. То обаче не е продукт на завършващ алгоритмичен процес. Според хипотеза Г, съзнанието не е изчислимо и не подлежи на научно изследване. В своята книга Роджър Пенроуз защитава хипотеза В. Като страничен резултат на това, следва че изкуствен интеленкт базиран на компютри не може да съществува. С това завършва първата част и започва втората - а именно, ако съзнанието се случва някъде в мозъка, а мозъкът е материя и следователно може да се изследва с методите на физиката, то как и какво е съзнанието. И тук следва една забележителна история за квантови сплитания и чехълчета. И една липсваща теория (не случайно подзаглавието на книгата е "В търсене на липсващата наука за съзнанието") - теорията на материята. Според Роджър Пенроуз, квантовата физика все още не е достигнала познанието на материята от което се нуждаем за да разберем съзнанието. Но има идея къде да търсим. По-точно къде да търсят теоретичните физици. Прави аналогия с Нютоновата теория на гравитацията, която изключително прецизно е описвала наблюдаваните при експерименти данни и Айнщайновата теория на относителността, която прави качествен скок в разбирането ни за пространството. Той очаква същото да се случи с квантовата физика, която сега изключително прецизно описва експерименталните данни, но не ни отговаря на въпроса какво всъщност е материята.
В книгата има много препратки към "Новият разум на царя: За компютрите, разума и законите на физиката".
Накратко - по-добра от фантастичен роман:)
Започнах с втората част, защото там е разковничето, което Роджър Пенроуз счита, че ще ни открехне вратата към един въпрос, който касае цялата книга - въпросът за това що е то съзнание и къде точно се случва. Първата част обаче е не по-малко вълнуваща. В нея се поставя въпросът, който днес е на дневен ред - изчислимо ли е осъзнаването. С други думи доколко един хипотетичен компютър (например много бърз и с много памет) би могъл на осъзнае нещо. За тази цел Роджър Пенроуз стъпва на теоремата на Гьодел и разглежда 4 основни хипотези, наречени А,Б,В,Г. Според хипотеза А, съзнанието е изчислимо. Според хипотеза Б, съзнанието не е изчислимо, но не съществува начин да бъде отличено от достатъчно сложен алгоритъм. Според хипотеза В, съзнанието не е изчислимо, но може да бъде научно изследвано. То обаче не е продукт на завършващ алгоритмичен процес. Според хипотеза Г, съзнанието не е изчислимо и не подлежи на научно изследване. В своята книга Роджър Пенроуз защитава хипотеза В. Като страничен резултат на това, следва че изкуствен интеленкт базиран на компютри не може да съществува. С това завършва първата част и започва втората - а именно, ако съзнанието се случва някъде в мозъка, а мозъкът е материя и следователно може да се изследва с методите на физиката, то как и какво е съзнанието. И тук следва една забележителна история за квантови сплитания и чехълчета. И една липсваща теория (не случайно подзаглавието на книгата е "В търсене на липсващата наука за съзнанието") - теорията на материята. Според Роджър Пенроуз, квантовата физика все още не е достигнала познанието на материята от което се нуждаем за да разберем съзнанието. Но има идея къде да търсим. По-точно къде да търсят теоретичните физици. Прави аналогия с Нютоновата теория на гравитацията, която изключително прецизно е описвала наблюдаваните при експерименти данни и Айнщайновата теория на относителността, която прави качествен скок в разбирането ни за пространството. Той очаква същото да се случи с квантовата физика, която сега изключително прецизно описва експерименталните данни, но не ни отговаря на въпроса какво всъщност е материята.
В книгата има много препратки към "Новият разум на царя: За компютрите, разума и законите на физиката".
Накратко - по-добра от фантастичен роман:)
July 26, 2025
Exactly a year ago, I closed The Emperor’s New Mind by Sir Roger Penrose, slid it onto my bookshelf, and just stood there for a second….The book didn’t just earn a spot on my shelf, it earned a permanent place in my head.
While I was reading the book, it felt, not just reading, but rather, I was thinking with him. And I love that. His ideas don’t rush past you, they unfold, give you space to chew on them, challenge you, and at times, leave you questioning what you thought you understood about reality, time, quantum physics or consciousness.
Sir Penrose has so much to offer, these books were written in the late 80s but the context is very much relevant in contemporary times. I’ve lost count of how many times I’ve skimmed YouTube watching his interviews. There's a real calm in the way he speaks, and his clarity is incredible.
Anyway, I could easily ramble about The Emperor’s New Mind for hours, but this note’s about the sequel, Shadows of the Mind: A Search for the Missing Science of Consciousness. I finished it last week and decided to finally sit down, gather all the half-scribbled thoughts and underlined passages I’d scattered across notebooks and margins, and shape them into something that looks like a review (but honestly feels more like notes to my future self).
Shadows of the Mind came out in 1994, and it picks up right where the Emperor left off, asking bold questions about consciousness, computation, and whether the brain can be fully explained by algorithms.
The book is not really about AI or quantum physics but it's about exploring “what” (and not “who”) we are at the fundamental level.
Sir Penrose thinks we are more than just simple machines or biological computers. He believes we access something deeper and more complex that we don't fully understand yet. According to him, for consciousness (being aware and having thoughts) to happen, comes from a type of physics or physical process we haven't discovered yet, which is built into the very fabric of reality.
The idea can be compared to listening to a symphony. Simply reading the sheet music (like analyzing the brain's computations) isn't enough to truly experience the music. To really appreciate it, we need to hear the sound, feel its effect, its vibrations, its presence in the air, and let its ineffable qualities resonate within us, qualities that current physics has yet to fully capture or explain.
Isn't this a profound idea, something to sit and marinate into?
More: Shadows of the Mind by Roger Penrose
While I was reading the book, it felt, not just reading, but rather, I was thinking with him. And I love that. His ideas don’t rush past you, they unfold, give you space to chew on them, challenge you, and at times, leave you questioning what you thought you understood about reality, time, quantum physics or consciousness.
Sir Penrose has so much to offer, these books were written in the late 80s but the context is very much relevant in contemporary times. I’ve lost count of how many times I’ve skimmed YouTube watching his interviews. There's a real calm in the way he speaks, and his clarity is incredible.
Anyway, I could easily ramble about The Emperor’s New Mind for hours, but this note’s about the sequel, Shadows of the Mind: A Search for the Missing Science of Consciousness. I finished it last week and decided to finally sit down, gather all the half-scribbled thoughts and underlined passages I’d scattered across notebooks and margins, and shape them into something that looks like a review (but honestly feels more like notes to my future self).
Shadows of the Mind came out in 1994, and it picks up right where the Emperor left off, asking bold questions about consciousness, computation, and whether the brain can be fully explained by algorithms.
The book is not really about AI or quantum physics but it's about exploring “what” (and not “who”) we are at the fundamental level.
Sir Penrose thinks we are more than just simple machines or biological computers. He believes we access something deeper and more complex that we don't fully understand yet. According to him, for consciousness (being aware and having thoughts) to happen, comes from a type of physics or physical process we haven't discovered yet, which is built into the very fabric of reality.
The idea can be compared to listening to a symphony. Simply reading the sheet music (like analyzing the brain's computations) isn't enough to truly experience the music. To really appreciate it, we need to hear the sound, feel its effect, its vibrations, its presence in the air, and let its ineffable qualities resonate within us, qualities that current physics has yet to fully capture or explain.
Isn't this a profound idea, something to sit and marinate into?
More: Shadows of the Mind by Roger Penrose
July 20, 2023
Roger Penrose’s books are, for me, challenging reading. “Shadows of the Mind” was so taxing on my cognitive faculties that, after starting to read the book, I put it back on the shelf after the first 100 to 200 pages. However, after some 20 years had passed, I decided to struggle further with my efforts to tackle this book. I did eventually finish it, and I regard the book as a “masterpiece”.
Is Penrose on the right track in trying to tie in microtubules with quantum physics in order to decipher how consciousness “arises” in the brain? I regard Penrose as miles ahead of Daniel Dennett’s “parallel processing” strategies for “explaining” consciousness. And I also believe that Penrose is getting closer to a solution to this awesome conundrum than Stanislas Dehaene with his “global workspace” model for “explaining” consciousness.
In spite of all the masterful efforts by scientists and philosophers to unravel the deep and profound mysteries inherent in our awareness of reality and our SELF-AWARENESS, my own conclusion is that the endeavors are essentially doomed before they even begin. Consciousness is too close to Ultimate Reality (Spirit, in other words) for humanity, with its materialist strategies, to ever decipher. The famous philosopher/mathematician, Alfred North Whitehead, might have come closer than any other human being, to date, to pinning down how consciousness and matter relate (how the physical and mental interact). Whitehead’s magnum opus, “Process and Reality”, proceeds very deeply into the nature of reality. But Whitehead, although acknowledging the existence of “God”, infinitely far underrated the power and glory of the true Creator God – the Infinite One.
I am endlessly fascinated by human efforts to explain the ultimate nature of all reality, when it is apparent to me that the puny human intellect can never do much more than scratch the surface of that which is truly Ultimate Reality. Humble surrender to that Reality is the soundest and most sagacious approach to take, and this approach will include a humble acknowledgment of human finitude and the need to be guided by Infinitude.
At any rate, the book under review gets high marks from me for its deep analysis of how consciousness MIGHT arise, with its powers that transcend computability, in conjunction with quantum physics and its interplay with neuronal microtubules. At the very end of his book (on page 420), Penrose wisely concedes:
“No doubt there are not really three worlds but one, the true nature of which we do not even glimpse at present.”
Is Penrose on the right track in trying to tie in microtubules with quantum physics in order to decipher how consciousness “arises” in the brain? I regard Penrose as miles ahead of Daniel Dennett’s “parallel processing” strategies for “explaining” consciousness. And I also believe that Penrose is getting closer to a solution to this awesome conundrum than Stanislas Dehaene with his “global workspace” model for “explaining” consciousness.
In spite of all the masterful efforts by scientists and philosophers to unravel the deep and profound mysteries inherent in our awareness of reality and our SELF-AWARENESS, my own conclusion is that the endeavors are essentially doomed before they even begin. Consciousness is too close to Ultimate Reality (Spirit, in other words) for humanity, with its materialist strategies, to ever decipher. The famous philosopher/mathematician, Alfred North Whitehead, might have come closer than any other human being, to date, to pinning down how consciousness and matter relate (how the physical and mental interact). Whitehead’s magnum opus, “Process and Reality”, proceeds very deeply into the nature of reality. But Whitehead, although acknowledging the existence of “God”, infinitely far underrated the power and glory of the true Creator God – the Infinite One.
I am endlessly fascinated by human efforts to explain the ultimate nature of all reality, when it is apparent to me that the puny human intellect can never do much more than scratch the surface of that which is truly Ultimate Reality. Humble surrender to that Reality is the soundest and most sagacious approach to take, and this approach will include a humble acknowledgment of human finitude and the need to be guided by Infinitude.
At any rate, the book under review gets high marks from me for its deep analysis of how consciousness MIGHT arise, with its powers that transcend computability, in conjunction with quantum physics and its interplay with neuronal microtubules. At the very end of his book (on page 420), Penrose wisely concedes:
“No doubt there are not really three worlds but one, the true nature of which we do not even glimpse at present.”
April 9, 2023
This book contains three parts. The first is philosophy. Penrose explains Godel's incompleteness theorem and Turing's halting problem and uses them to argue that no computer can be conscious in the sense of being aware of what it's doing. The idea is that a computer wouldn't be able to come up with a solution to the halting problem without accepting that there may be some flaws in its own logic but by definition there would be no flaws in its logic. Penrose concludes that Humans do not use a sound algorithm to come up with mathematical ideas. Applying this to AI, one would hope that an intelligent agent on a computer would be able to do mathematics as well as humans, but the argument is that this leads to a contradiction and so could be viewed as an argument against superintelligence on classical computers. (This is at odds with AI saftey theory where the theorists don't care whether the computer is self aware or not.)
The second part is a fairly detailed introduction to quantum mechanics and then goes on to suggest the need for new physics that cannot be simulated. Otherwise one has to conclude that consciousness must be some sort of spiritual thing, as current physics can in principle be simulated on a computer. The idea presented here is that the physics of measurement of quantum systems by large entangled states need to have a better theoretical foundation, i.e. Schrödinger's cat is ridiculous and can't happen in reality. He rather dubiously claims that quantum gravity may have an answer by making such the wavefunctions in such experiments unstable. This is a good idea, but it's not clear why this couldn't just be a feature of quantum mechanics already. Another, more promising, application of quantum gravity discussed is that it may not be able to be simulated, and so would potentially get round some of the issues discussed in the first part.
The third part then uses this to argue that there must be some quantum mechanical action in the brain, as otherwise the brain would be classical and then be able to be simulated. Penrose points out that brain cells (as well as other cells) contain things called microtubials which may contain entangled water molecules. This water may act much like qbits in modern quantum computers, and so the brain could be a large entangled quantum system. These microtubials control some part of the synapses in neurons, so the idea is that the brain has two components, a quantum mechanical part which then causes the classically observable neuron activity. Penrose argues that anesthetic, generally being made of polar molecules, disrupts this entanglement, leading to a loss of consciousness.
The ideas presented are thought provoking, but it's not clear who the book is aimed at. Penrose himself often encourages the reader to skip over parts of the text. I feel like anyone who really understood the first part would probably know a fair bit of quantum mechanics, so wouldn't need to read much of the second part, but the second part may be a bit complicated for anyone who didn't really understand the first part and perhaps isn't enough to really appreciate the third part of the book anyway.
The second part is a fairly detailed introduction to quantum mechanics and then goes on to suggest the need for new physics that cannot be simulated. Otherwise one has to conclude that consciousness must be some sort of spiritual thing, as current physics can in principle be simulated on a computer. The idea presented here is that the physics of measurement of quantum systems by large entangled states need to have a better theoretical foundation, i.e. Schrödinger's cat is ridiculous and can't happen in reality. He rather dubiously claims that quantum gravity may have an answer by making such the wavefunctions in such experiments unstable. This is a good idea, but it's not clear why this couldn't just be a feature of quantum mechanics already. Another, more promising, application of quantum gravity discussed is that it may not be able to be simulated, and so would potentially get round some of the issues discussed in the first part.
The third part then uses this to argue that there must be some quantum mechanical action in the brain, as otherwise the brain would be classical and then be able to be simulated. Penrose points out that brain cells (as well as other cells) contain things called microtubials which may contain entangled water molecules. This water may act much like qbits in modern quantum computers, and so the brain could be a large entangled quantum system. These microtubials control some part of the synapses in neurons, so the idea is that the brain has two components, a quantum mechanical part which then causes the classically observable neuron activity. Penrose argues that anesthetic, generally being made of polar molecules, disrupts this entanglement, leading to a loss of consciousness.
The ideas presented are thought provoking, but it's not clear who the book is aimed at. Penrose himself often encourages the reader to skip over parts of the text. I feel like anyone who really understood the first part would probably know a fair bit of quantum mechanics, so wouldn't need to read much of the second part, but the second part may be a bit complicated for anyone who didn't really understand the first part and perhaps isn't enough to really appreciate the third part of the book anyway.
September 23, 2018
This book is great feat of human logic. It gives in a logical analysis why the human brain can't be a mere computational machine like computers. The author, Sir Roger Penrose, who is an acclaimed mathematical physicist, asserts on the basis of Godel's incompleteness theorems, that our brain's perception is beyond the constraints dictated by these theorems (which are true for the mathematics and the algorithms operating in computers). We wouldn't be able to grasp the mathematical concepts and to formalize new concepts if our brains and consciousness would be confined by those theorems' constraints. The author asserts that our brains operate by rules which require consideration of new Physics, particularly the Quantum Physics, in order to explain the rise of consciousness out of the brain. He gives practical examples by using AI (Artificial Intelligence) to show why brains can't be just some extended AI. Then he gives other practical examples from brain cells' basic structures to show how brains might use the mysterious principles of Quantum Physics to function and to having the abilities which surpass immensely the most advanced digital AI and that any digital AI wouldn't ever possess them in principle.
The drawback of this book is that it contains extensive mathematical-philosophy discussions centered around Godel's incompleteness theorems, using many symbols in those discussions. The author himself advises most of the readers to omit such sections. But even besides it, IMO, the author's language is not always so friendly for the average reader in his explanations and conclusions about those discussions above.
The drawback of this book is that it contains extensive mathematical-philosophy discussions centered around Godel's incompleteness theorems, using many symbols in those discussions. The author himself advises most of the readers to omit such sections. But even besides it, IMO, the author's language is not always so friendly for the average reader in his explanations and conclusions about those discussions above.
March 9, 2019
A difficult read, I skipped most of the middle section owing to my undergraduate being in physics, and the middle section presents an introduction to quantum mechanics. I read the initial chapters, which go over an argument for why consciousness is not mere computation. THe final section goes over the possibility for microtubules to be units of neuronal processing, instead of the basic unit being the neuron, this greatly expands the computational capacity of the mind.
Overall a speculative book, and I noticed Penrose worked out a lot of this on his own, as the references section is shorter than many books of this type. THis does present an interesting 'new' take on a topic which has been explored by others in such glancing depth.
Overall a speculative book, and I noticed Penrose worked out a lot of this on his own, as the references section is shorter than many books of this type. THis does present an interesting 'new' take on a topic which has been explored by others in such glancing depth.
May 14, 2019
Roger Penrose her zamanki titizliği ile konuyu en temellerinden ele alıyor ve önemli çıkarımlarda bulunuyor. Penrose sadece başkalarının çalışmalarını derleyen bilim yazarlarından değil. Önemli ve orijinal araştırmaları var. Bu nedenle bir şey yazdığında okumadan geçmiyorum.
Ne var ki dili problemli. Kimi zaman cümleleri bir paragraf uzunluğunda ve üç beş kere okuyunca ancak anlayabiliyorum. Yazdıklarını önemsediğim için dip notlara kadar okumaya kalkınca bir ayda ancak bitiyor kitap. İyi tarafı ise şu : bazı detaylara girmek istemeyenlere hangi bölümleri atlayarak gidebileceklerini söylüyor. Dolayısı ile ana fikri kaçırmadan ve bütünlüğü bozmadan okuyabilirsiniz. Özetle içindeki fikirler ve çıkarımlar çok önemli, kitaplıkta mutlaka bulunmalı ve başvuru kitabı olarak kullanılmalı.
Ne var ki dili problemli. Kimi zaman cümleleri bir paragraf uzunluğunda ve üç beş kere okuyunca ancak anlayabiliyorum. Yazdıklarını önemsediğim için dip notlara kadar okumaya kalkınca bir ayda ancak bitiyor kitap. İyi tarafı ise şu : bazı detaylara girmek istemeyenlere hangi bölümleri atlayarak gidebileceklerini söylüyor. Dolayısı ile ana fikri kaçırmadan ve bütünlüğü bozmadan okuyabilirsiniz. Özetle içindeki fikirler ve çıkarımlar çok önemli, kitaplıkta mutlaka bulunmalı ve başvuru kitabı olarak kullanılmalı.
October 8, 2024
Основная идея книги - мозг, как квантовый компьютер, хотя по моему, я уже где-то слышал про это раньше. Раз так, то можно делать вывод, что мы никогда не сможем познать наш собственный мозг, ибо создать квантовый компьютер на мой взгляд невозможно в принципе. Правда уважаемый мною (и всем человечеством) Роджер Пенроуз так не считает. В любом случае книгу легким чтением не назовешь, по моему она даже не про мозг. Пятую главу можно предложить почитать отдельно как хорошее введение в квантовую теорию для гуманитариев, чтобы понимать ее проблематику на качественном уровне. Но почитать нужно несколько раз, не менее трех точно.
August 26, 2022
What is consciousness? Many interesting concepts were introduced but I have to admit I skimmed over large sections of this book. I am only human and the mathematics were way over my head. If you have any interest in theories on consciousness I would recommend skipping to Chapter 7 where Penrose ties together Quantum theory and the functions of the brain. Biological structures (i.e. microtubules) are described in detail which may have a role in quantum processes. Could there be an explanation for consciousness here? Only time will tell.
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