First, a warning of sorts: this book of 602 pages is not light reading. This strange hybrid of a philosophy treatise and a science text doesn't even have a very satisfying conclusion. For a book that sets out to answer, or at least attempt to answer, what consciousness is, the answer, when it came, lacked conviction. I'm sure that the author was convinced; the fault lies with the writing. Science communication (and I distinguish this quite clearly from communications between scientists: science communication to the lay-person is an art form, not an application of the scientific method) is not only about the transmission of information and knowledge: it is also about getting logical agreement and emotive buy-in from the reader. A popular science book that doesn't provide a good 'satisfying read' serves no one.
This is disappointing, for the background information Professor Penrose provided (which in a popular science book such as this one is essential to leading the non-expert to the the author's conclusion in an inevitable and logical way) is a good and solid introduction to the fundamentals of logic, artificial intelligence and modern (i.e.20th century) physics. It is unfortunate that the robust background information could not build up to a firm pronunciation (the author, was in the typical English gentleman way, far too apologetic) of Professor Penrose's belief that consciousness is non-algorthmic, (possibly) works because of non-local effects stemming from the Einstein-Poldolsky-Rosen paradox, does not cause vector-state reduction (refer to the 'Schrodinger's cat' thought experiment), and will require further improvements in our understanding of the Grand Theory of Everything (in which the marriage of quantum electrodynamics and general relativity is only the first step) before any description is possible.
Don't get me wrong: this book has its brilliant moments. The introduction to computing and Turing's Test is clear, and the arguments between a deterministic universe versus a computable universe compelling. The physics discourse is heartwarmingly nostalgic of my undergraduate course and actually taught me a new thing or two. The chapters on existing knowledge of the human brain and consciousness were well written and informative (though I wish there were more details). My favourite paragraph in the entire book is this:
"Many philosophers and psychologists seem to take the view that human consciousness is very much bound up with human language. Accordingly, it is only by virtue of our linguistic abilities that we can attain a subtlety of thinking that is the hallmark of our humanity - and the expression of our very souls. it is language, according to this view, that distinguishes us from other animals, and so provides us with our excuse for depriving them of their freedom and slaughtering them when we feel that such need arises. It is language that allows us to philosophize and to describe how we feel, so we may convince others that we possess awareness of the outside world and are aware of also ourselves."
This had me lean back on the chair to marvel at the idea that somehow, the very language that communicates this thought to me is the very embodiment of consciousness. This is a simple concept, yet it hides such complexity behind its 'obviousness'. What of dolphin consciousness/intelligence? What of two people speaking completely different languages? Surely there are ways of bridging the gaps! (Just imagine a first contact situation, where two aliens... sorry, beings.... are trying to learn from one another how each other counts.) And if so, does it not favour an objective universe, and not a subjective one? The sheer importance for the role of imagination in a subjective universe defies belief, and I'd go with Occam's Razor on this one.
In the fifteen years since this book was written, there has been progress in the field of super-string theory which goes some way to further explain the fundamental 'realities' of this universe we live in. My feel is that if Professor Penrose had these data back then, his arguments might have altered a little, but the fundamental arguments would still be the same. As our knowledge of clinical consciousness and the elementary (excuse the phrase... would 'fundamental' be better?) physics increase, how can we use science explain consciousness? With new, unknown science, it seems.