Rating: 
Summary: A Remarkable Tour of Remarkable Things
Review: This book seeks to counter intimations from the AI community that the only reason AI has not yet succeeded is the failure to build large enough or complex enough processing machinery. Drawing from a variety of topics in physics and mathematics, Penrose seeks to illustrate many anomalous areas that seem beyond the capability of any kind of artificial reasoning approach currently known, regardless of the amount of sophistication or processing power thrown at them. An "artificial intelligence" that cannot deal with these phenomena, Penrose argues, cannot really lay claim to be what it purports to be -- and we are nowhere near having the tools to do so. Penrose, indeed, is obviously skeptical as to whether it is possible to have such tools.The book does not end with a grand flourish and "Aha!" The reader is left to draw his or her own conclusions. I found the discussions of specific topics absolutely absorbing, even though I am not a mathematician or physicist. It required a fair amount of focus and concentration on my part to stay with him. It was worth it. For an educated lay reader with an interest in current science, this is a fascinating and important book.
Rating: 
Summary: Strange new world
Review: My guess is that the ideas in this book are what happens to an internationally acclaimed mathematician/physicist as he tries to deal with quantum non-locality. Quantum non-locality is getting some physicists to think about the position of the mind in physical reality. The interesting thing about this book is seeing how a great mind attacks problems in computability, new physics, old physics, mathematics, philosophy, and especially AI. This book tries to kill AI. The discussion methods used to explore these ideas are sophisticated and semi-technical and very appropriate and interesting. The conclusions however are off the wall and verge on the metaphysical. I wouldn't recommend this book for light reading or light thinkers. It is worth the price just to see how someone like Penrose thinks and does problem solving.
Rating: 
Summary: It might be interesting, but I never got far enough to tell
Review: Penrose' book might be a good one, but it urgently needs the working of a good editor. If you plan on reading the book prepare your self to encounter an average of 3-4 exclamation marks per page and lots of parenthesized sentences. If you don't mind reading a book like this! (and sentences like this don't bother you at all) then this might be the book for you! It is not for me!
Rating:
Summary: Quantum liverwurst
Review: I can't pretend to have fully understood this opaque book, but the underlying technical idea seems to go something like this: 1) Since the brain is not yet comprehended, perhaps it is fundamentally incomprehensible and. 2) since we generally accept the notion that at the quantum level, things are incomprehensible, in the classical sense, this might just be the level at which the brain, as an incomprehensible machine, actually goes about its daily business, thinks its little thoughts, et cetera. In the conventional view, the brain is a biochemical machine. That is to say, it is an electromechanical device in which large molecular moving parts govern and gate the flow of ions. The chemistry of macromolecules is extremely mechanical -- in the classical, traditional, 19th century sense of the word mechanical. These molecules are in fact small watchworks. They change their shapes as they gain and lose energy. Biochemistry is the study of these hopelessly classical machines - their structure, energetics, provenance and mechanism of action. If you can understand a steam engine, you can understand neurochemistry. But to apply quantum physical principles to describe the workings of the brain one must abruptly change down to a wholly different operating scale -- make a radical shift in focus from the whopping cellular and macromolecular scale all the way down to the teeny-weeny dimensions at which quantum effects can be observed. Okay, so maybe this is the right place to look, why not? But if it is indeed, then shouldn't we also inquire about the quantum effects underlying the workings of our second most complicated organ, the liver? We don't completely understand the liver, either. Perhaps we never shall. It is dazzlingly complex. Are its mystery mechanisms - well, unknowable? Not rule based? Incomprehensible? For the price of this book, I suggest you go out to dinner. As you digest it, ask yourself (seriously, now) whether any quantum effects might be at work in your liver. Does it tickle, etc. If you think it seems like a silly question, you're right. It really is. If you're interested in recent progress on the problem of how the brain might work, um, at the macro level, you might try Spikes, by Rieke et al, or Kandel & Squires new book, Memory. For another mathematician's venture into neuroscience see also Von Neumann's beautifully crafted essay, the Computer and the Brain, which has just been re-published. Finally, maybe Ashcroft, in his new book on Ion Channels, has some hints.
Rating: 
Summary: Emperor's without clothes
Review: No, I'm joking. This is by far the best exposition of...what ? Basically, all the stuff, ranging from AI & algorithms to classical and quantum mechanics, thermodynamics and basic tenets of Big Bang cosmology, is densely packed in 480+ pages & rushes vertiginously the the author's central interest- brain/mind problem & his particular answer to the "why consciousness" mystery. On the strong side- Penrose has most lucidly expounded classical and quantum paradigmata ( plus thermodynamics and orthodox cosmology ). I think his finest writing is contained in these chapters/passages. Chapters from 1-4 ( with the possible exception of chapter 3. ) are a dry read & not illuminating at all. Frankly, I'd say the entire AI, the Turing machine & computability "mythology" is just a scholiasts's fodder, a scholastic verbiage lacking in true cognitive strength. Ultimately: where does Penrose stand ? Evidently- he is a "refined" reductionist/epiphenomenalist. I'd say his "consciousness" theory ( he's done not a few papers with Stuart Hameroff on Orch OR model ) is not a breakthrough at all. For better works on quantum physics, one should consult David Bohm's works ( apart from classical textbooks of Landau, Messiah or Sakurai ); for a more thought-provoking "brain" musings- Jean Pierre Changeux & his L'Homme Neuronal. So, although the author has not shown much conceptual audacity and originality, I'm giving this book 4 stars for excellent exposition of chunks of physics for laymen.
Rating:
Summary: Fascinating Journey well worth undertaking
Review: This book is an extremley challenging read but of all the science books I have read I feel this one covers the subjects concerned in the most depth. While I would agree with the reviewers who feel that Penrose has put together a patchwork arguement I am nevertheless grateful that he has delved into the areas of chaos theory, relativity , Godel's theorom , quantam physics and others as his descriptions are thought-provoking and fascinating. Penrose ,rather than giving brief outlines of the area he is covering , is prepared to go into the intracises , leaving one deeply enriched. Rather than treating the book in a single context , I would recommend taking each chapter as it comes , paying carefull attention to the wonders of what Penrose is describing. Although I doubt very much if it was his intention, I would like to believe that Penrose needed an excuse to put all these ideas in a single book , and the Artificial Intellegence debate provided him with one
Rating: 
Summary: so-so
Review: This book has basically two parts: one is an explanation of quantum physics, and the other is an attempt to show that the human mind cannot be represented by a computer, possibly because of quantum interactions in the brain. The first part was hard for me to understand, not because it's poorly written, but because the subject is very difficult. The second part I found very flawed. The author seems determined to show that the brain is not just a computer, and gives all benefit of the doubt to this theory, and none to any counterarguments. Much of his argument is based on intuition - the conscious mind *seems* to work a certain way, we *feel* that a certain kind of thinking is non-algorithmic - which is not very persuasive.
Rating:
Summary: Brave Postulations!
Review: I can't say enough for this book. Whether or not you agree with Penrose's idea that science will never be enough to grasp human consciousness or not, this book is a fascinating journey into Quantum Physics, Godel's Incompleteness Theorem and a good time to evaluate your own thoughts on human consciousness based on logic and science rather than a spiritual approach regardless of your feelings on Penrose's postulations. I must give a word of caution to a would-be reader, this is not a book for someone not willing to get through some technical stuff. If you only want to be spoon-feed an opinion without understanding HOW the opinion was formed, this is not the book for you. HIGHLY RECOMMENDED!
Rating:
Summary: Want to go fishing for non-algorithmic thought?
Review: Penrose is inviting the reader to a weekend fishing expedition. He hopes to catch a whopper and get a group snapshot -- refutation of hard AI. The bait he offers is rather strange: quasicrystaline analogy of dendritic spine growth and contraction; a Platonic, timeless world of mathematical truth; something he calls CQG (Correct Quantum Gravity) with its one graviton criterion and two quantum processes he calls U and R. If you swallow this strange bait then you are hooked and don't blame anyone else when you wake up sizzling in frying pan oil. On the plus side Penrose throws caution to the wind in trying to pin down the ever elusive human consciousness. He constructs for the reader a mental mirror in which to view the Tower of Babel world of Artificial Intelligence. However, in trying to use the child's view metaphor positively he makes the mistake of rattling off a string of "whys" that can never be answered. Setting up the mind-body dichotomy in any form presents only a chicken-egg question. If consciousness is located in the reticular formation of the brain, why there? As to memory -- just because the sound of music can be stored on magnetic tape, the sounds replayed are only virtual or copycat sound from the real, live orchestra. The brain may be merely a recording device and consciousness only a playback of this recording. Penrose is very puzzled and perplexed that his geometrically formulated ideas don't translate well into words. Penrose laments that consciousness may not possess the active skills (free will) and is left with merely a spectator role. His speculations lead the reader into the quantum vacuum foam, to a head full of constantly emerging sub-quantum singularities or submicro-wormholes, framing human consciousness as a model for the mind of a deity. Amen.
Rating:
Summary: Well worth the read
Review: I do not believe that previous reviewers are at all correct when calling this book a "cult book" or attempting to completely refute the conclusion of this book. For one thing, this book provides a lot more than just Penrose's conclusion, written in an understandable, yet extremely in-depth style. The discussions of Turing machines, quantum physics, and consciousness are very thought-provoking. Although Penrose's conclusion is not proven, and may even be incorrect, the ideas he presents are well worth the read.
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