Rating: 
Summary: For physicists, mathematicians or geniuses only
Review: On the back of the book jacket it states that this book provides an "accessible" introduction to Roger Penrose's ideas. This is simply false, unless you are a physicist, a mathematician or a genius. For all others (in which category I fall), this book is close to incomprehensible.
Roger Penrose is brilliant, has a wonderfully clear mind, and can write beautifully and clearly. I think that _The Emperor's New Mind_ and _Shadows of the Mind_ are wonderful books. Penrose can make extremely difficult ideas wonderfully clear, by breaking down complex arguments into clear simple steps. Some pages of Emperor's and Shadows take a long time to understand, (I must admit that I have read quite a bit less than all of either book), but the argument is spelled out so clearly that with effort and patience it can be fully understood. Penrose, I think, understands the questions he is wrestling with as well as any one alive, and his is a mind of great depth as well as clarity. Even if you don't find his arguments entirely convincing, you can't help but learn a great deal from these books, and develop insights of great value. What went wrong with _The Large, the Small and the Human Mind_? I think the key to answer lies in a comment Penrose makes on page 105, where he writes "The first 200 pages of _Shadows of the Mind_ were devoted to trying to show that there are no loop-holes in the argument that I am goind to give you." He then gives his argument in a few pages. The main part of the book (not including the replies of others and Penrose's replies to these replies) is just 139 rather small pages long. The book has many paragraphs like the following:
"The first is the Geroch-Hartle scheme for quantum gravity, which turns out to have a non-computable element, because it invokes a result, due to Markov, which asserts that topological 4-manifolds are not computationally classifiable. I shall not go into this technical matter, but it does show that this feature of non-computability has already come up in a natural way in attempts to combine General Relativity and quantum mechanics."
If, like me, you don't know what the Geroch-Hartle scheme is, and you don't know what topological4-manifolds are, you really won't know what to make of this paragraph. By "not going into this technical matter" Penrose is not omitting a minor technical detail of interest only to a select few, he is leaving readers like me completely baffled.
Penrose tried to write a short book that would give a clear idea of his basic ideas, and I think he failed. I know that he can make complex ideas wonderfully clear when he takes the time. In this book he has shown that, at least on this occaision, he can not write a book that is both brief and clear.
Here is another example, this time from Penrose's response to Abner Shimony's comments: (pages 176-7)
"Abner mentions Mielnik's non-Hilbertian quantum mechanics....In ordinary quantum mechanics, the space of density matrices consitutes a convex set, and the 'pure states', which would have a single state vector description, occur on the boundary of this set. This picture arises from an ordinary Hilbert space, being a subset of the tensor product of the Hilbert space and its comples conjugate (i.e. dual)."
Did you understand that? If so, you might learn a great deal from this book.
There are a number of topics that I have read about previously in other books, for example, non locality, Schroedinger's cat, the EPR experiment. In almost every case, Penrose's presentation was the worst I have seen. Probably everything he says is quite correct, but the presentation is so compressed that it was usually almost impossible for me to follow.
There are sections that I could follow, but even there he was so sketchy that I ended up with only a vague idea of _why_ he believes what he does, even when it was clear _what_ he believed. For instance, on pages 100-101 he is concerned with four approaches to awareness, which he labels A through D. "D" is as follows:
Awareness cannot be explained by physical, computational, or any other scientific terms.
Here is, in its entirety, what he has to say about "D":
Finally, the is always viewpoint D, according to which it is a mistake to look at these issues in terms of science at all. Perhaps awareness cannot be explained in scientific terms.
Penrose likes one of the other four positions, which is clearly stated, as is "D." But I would have liked to see Penrose develop in detail the reasons for his rejecting D. He does this only indirectly, by arguing for his preferred alternative, and this quite briefly.
I think that I understood enough of the book to say that if Penrose turns out to be even roughly correct, he will be regarded as one of the great geniuses of the century. His proposals are bold, and deal with questions of the greatest interest. If only I could have followed his arguments!
I hope that somebody who can follow his arguments posts a review.
Rating: 
Summary: Lucid approach to establish a quantum-based mind theory
Review: Penrose concisely manages to give us an overview about 3 somehow interconnected fields, the mathematically described large-scale world, the deterministic quantum microcosm and the recently emergent mind science. His major aspiration is to see the new generation of scientists erecting a bridge between the quantum world and the always controversial substance of conscience.Having in his mind (in a neo-platonic way) the idealistic nature of mathematics that apply to the physical world as a well-justified model, he firstly presents some themes from cosmology and abstract mathematics (e.g. hyperbolic, Riemann geometry), and why, in his opinion, Guth's inflationary universe theory, has weak points (see also Penrose's book- Difficulties with inflationary cosmology) In chapter 2 ,quantum physics related, he gives us interesting examples (the paradox& puzzles reference shows his great sense of humor) and explain us how wavefunction's reduction can assist us to deal with the probabilistic nature of events in this level.
In the most interesting third one, he is concerned to lay an in-depth foundation between quantum procedures through neurons, so as to explain his main belief - brain function (that creates conscience) can't be simulated through A.I. Even though I tend to prefer J.Searle opinion (presented in his book Mind,Brain & Science) Penrose's points are adequately justified, thus leaving an open window for Free Will. In the next three chapters certain Penrose's point's are opposed from Shimony (physician, philosopher) Nancy Cartwright(logician, philosopher) and the renowned Steven Hawking.
Shimony in a formalistic language, but slightly excessive for the common reader, finally makes a conjecture about a hyperselection law, in order to avoid quantum dualism, while Mrs Cartwright sets a contronversy against the usefulness of a perception that sets Physics the only explanatory science for mind theory and not for example Biology.(which for Penrose is reduced to Physics)
Hawking denies an indispensable and direct correlation between quantum gravity and the yet inextricable conscience and in chapter 7 Penrose responds to all so as to end this dialectically fair and fruitful discussion. Overall this was worth my time, not only for this subject's great interest but because Penrose explains his thesis, clearly and distinctly.The uprising need for 'popular' science is reflected and adequately satisfied through this lucid book which succinctly presents a contemporary overview in a 'hot' scientific field. Even non-expert readers (no special background in maths or physics is needed) will be able to follow and admire the ongoing revolution of scientific thought.Given it was written in'97 I'm looking forward and will benevolently embrace another similar work of a splendid thinker such as Penrose
Rating:
Summary: The revolutionary in science
Review: Roger Penrose's original and provocative ideas about the large-scale physics of the Universe, the small-scale world of quantum physics and the physics of the mind have been the subject of controversy and discussion. These ideas were proposed in his best-selling books The Emperor's New Mind and Shadows of the Mind. In this book, he summarises and updates his current thinking in these complex areas to present a masterful summary of those areas of physics in which he feels there are major unresolved problems. Through this, he introduces radically new concepts which he believes will be fruitful in understanding the workings of the brain and the nature of the human mind. These ideas are challenged by three distinguished experts from different backgrounds: Abner Shimony and Nancy Cartwright as philosophers of science and Stephen Hawking as a theoretical physicist and cosmologist. Roger Penrose concludes with a response to their thought-provoking criticisms.
To see a scientist of Penrose's ability, stature and achievement toss large parts of modern physics into the air as though juggling balls and try to keep them aloft while marshalling them into a coherent pattern is a thing to behold. It is a wonderful illustration of a first-rate scientist doing what first-rate scientists have always done: make bold conjectures and display them for others to confirm, refute or amend
Rating:
Summary: Penrose attacks problems others just try to ignore.
Review: The most important problems in physics and philosophy are, in order of increasing difficulty: 1) Unifying quantum mechanics and gravity
2) Solving the paradoxes of quantum mechanics.
3) Explaining the "unreasonable effectiveness of
mathematics in the physical sciences".
4) Explaining consciousness. In this slim volume, Penrose attacks all four problems head on! His solution of problem 3) is a form of neo-Platonism that allows him to treat mathematical progress as a real form of discovery, rather than an arbitrary creation of human artifacts. His solution of problems 1), 2) and 4) consist in well, assuming that they are somehow related, so they are actually a single problem, which he does not really solve! I strongly agree with Penrose's solution of problem 3), but I have strong doubts about the rest. This is still a very good book, because, at least, it tries to solve problems that others, instead, just choose to ignore. Also, the exposition of non-problematic aspects of physics is very good, like the explanation (on pages 54-55 of the paperback edition) of the omnipresence of quantum mechanics in ordinary life and technology. This is a very important insight that many other popular expositions of quantum mechanics completely miss. We really live in a quantum world, because life is not possible in a classical, Newtonian, world!
Rating:
Summary: Penrose attacks problems others just try to ignore.
Review: The most important problems in physics and philosophy are, in order of increasing difficulty: 1)Unifying quantum mechanics and gravity
2)Solving the paradoxes of quantum mechanics.
3)Explaining the "unreasonable effectiveness of
mathematics in the physical sciences".
4)Explaining consciousness. In this slim volume, Penrose attacks all four problems head on! His solution of problem 3) is a form of neo-Platonism that allows him to treat mathematical progress as a real form of discovery, rather than an arbitrary creation of human artifacts. His solution of problems 1), 2) and 4) consist in well, assuming that they are somehow related, so they are actually a single problem, which he does not really solve! I strongly agree with Penrose's solution of problem 3), but I have strong doubts about the rest. This is still a very good book, because, at least, it tries to solve problems that others, instead, just choose to ignore. Also, the exposition of non-problematic aspects of physics is very good, like the explanation (on pages 54-55 of the paperback edition) of the omnipresence of quantum mechanics in ordinary life and technology. This is a very important insight that many other popular expositions of quantum mechanics completely miss. We really live in a quantum world, because life is not possible in a classical, Newtonian, world!
Rating: 
Summary: It just doesn't work...
Review: Turned off by the strong AI type point of view of consciousness, yet looking for a scientific explanation, I have repeatedly turned to Penrose's work hoping he would have enlightening ideas. At first, he seems to be on the right track, but when he starts making conclusions, things go awry.
As a biology student, I can say that his understanding of biology seems mediocre at best. And physics may be even worse - in fact his skepticism about the "flatness" of the universe has recently been rendered bascially obsolete.
I feel that the unified brain quantum undulation camp, if you will (penrose, zohar) paint themselves into a frightful corner. For instance, penrose never explains why his microtubule ideas would apply to the brain in particular...we've got oodles of them in every cell in our body! Basically, these ideas try to strike out against the strong AI poing of view, but actually create a new version of it! It's not the neuron construction, they say, instead it's a mechanism even more arbitrarily linked to the brain!
Penrose seems to be a great mathematician...and should stick to that. Still searching for explanations...
Rating:
Summary: It just doesn't work...
Review: Turned off by the strong AI type point of view of consciousness, yet looking for a scientific explanation, I have repeatedly turned to Penrose's work hoping he would have enlightening ideas. At first, he seems to be on the right track, but when he starts making conclusions, things go awry.
As a biology student, I can say that his understanding of biology seems mediocre at best. And physics may be even worse - in fact his skepticism about the "flatness" of the universe has recently been rendered bascially obsolete.
I feel that the unified brain quantum undulation camp, if you will (penrose, zohar) paint themselves into a frightful corner. For instance, penrose never explains why his microtubule ideas would apply to the brain in particular...we've got oodles of them in every cell in our body! Basically, these ideas try to strike out against the strong AI poing of view, but actually create a new version of it! It's not the neuron construction, they say, instead it's a mechanism even more arbitrarily linked to the brain!
Penrose seems to be a great mathematician...and should stick to that. Still searching for explanations...
Rating:
Summary: Biology Contradicted.
Review: What I am writing here in no way does justice to the book, I am merely trying to add a corrective to the way the book is reviewed. With Penrose, biology and the brain itself become epiphenomena. Biology loses its status as protected economic mythology (by default, not in the book). To become a neurobiologist (for instance) one usually has to accept at least some of the assumptions of the discipline or accept some responsibility for them; even by the questions Penrose raises he is fundamentally undermining such disciplines (even categorically) and at the same time seriously calling into question the judgment of their adherents. After all why would one have accepted or promoted such polluted theories when (after the fact) clarity was there all along... unless there was another motive. So more than their judgment is at stake, this work even calls into question their character as reflected in their basic sense of things. What are they going to do? Reform? It calls into question their basic forum.
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