Shadows Of The Mind

Shadows of the Mind: A Search for the Missing Science of Consciousness by RogerPenrose 1996 ISBN 0195106466

There's also a very interesting discussion of the book's thesis at This gives JohnMcCarthy of Stanford and eight other US computer scientists, philosophers and logicians a chance to try and hit back on behalf of the AI community (and perhaps the AmericanCulturalAssumption that a poor Brit can't possibly know what he's talking about, given the meagre size of his research budget).

I have to admit that I don't find all the arguments very easy to follow but I love just reading the keyword list: artificial intelligence, free will, Gödel's theorem, mathematics, microtubules, Platonism, quantum mechanics. There's got to be something for everyone there.

StephanHouben closes his comments on Penrose's earlier but closely related book, TheEmperorsNewMind:

Penrose also discusses the viewpoint that the state vector actually never reduces, and also the multiple universe interpretation. With these interpretations, quantum mechanics remains deterministic. But Penrose rejects them (with a CommonSense argument, not the most reliable guide when roaming through quantum land).

Penrose isn't alone among first rate scientists in reaching for OccamsRazor in evaluating the multiple universe interpretation. The thing to emphasize is that the thrust of his argument in both books is entirely scientific, which is part of what makes them so valuable. He writes in the third paragraph of ShadowsOfTheMind:

In this book, I shall attempt to address the question of consciousness from a scientific standpoint. But I shall strongly contend - by use of scientific argument - that an essential ingredient is missing from our present-day scientific picture. This missing ingredient would be needed in order that the central issues of human mentality could even be accommodated within a coherent scientific world-view. I shall maintain that this ingredient is itself something that is not beyond science.

Penrose certainly writes in a popular style but his deep respect for the ScientificMethod comes through in every chapter. In later chapters, he gives some fascinating details of the very mysterious experimental evidence on the nature of consciousness and its relationship to time, which few scientists from other disciplines seem to have looked into seriously. Certainly not many of them have taken trouble to let the general public know that they don't have a clue how to figure the current evidence out! Just as he would in cosmology or particle physics, Penrose takes the experimental evidence very seriously. He goes on to argue that some of the very weirdest parts of current quantum gravity speculation, including closed timelike lines (which might usefully allow an observer a second chance to experience the same time points!) may be needed as part of the unified picture that is finally used to explain consciousness.

Penrose makes it very clear where his formal, logical arguments end and his speculation begins. Unlike some scientists, he does show respect for the intuitions of human beings with less brain power than himself, which is fortunate for most of us. Yet, as physicists have had to get used to in the last century, he feels that the experimental evidence is forcing us to consider ideas which are about as far from CommonSense as one could possibly imagine. I for one am very grateful that he's taken the time to try to explain some of these reasons to us lesser mortals, some of whom hopefully have not yet lost our ability to wonder both at the universe and the amazing "miracle" presented to us every time we enjoy a discussion with a fellow human being.

-- RichardDrake


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