Keith Devlin reviews The Large, the Small and the Human Mind by Roger Penrose

THE story so far: episode 1 takes place in 1989, when the brilliant and charismatic Oxford mathematician and physicist Roger Penrose writes a book called The Emperor's New Mind. The book attacks artificial intelligence (Al) as a theory of mind and proposes a radically new theory based on practically all of modern physics. Although heavy going, it swiftly becomes a best-seller around the world.

Mathematicians, philosophers, cognitive scientists, physicists and countless others around the world mount separate, but sustained attacks on both Penrose's overall programme and on specific parts of his argument. The AI folk were up in arms as well, but as a certain Mandy Rice Davis said long ago in quite a different context, "Well, they would say that, wouldn't they?"

Episode 2 occurs in 1994 when, responding to his critics, our hero writes Shadows of the Mind. Fully half of this is an attempt to refute technical objections that had been levelled against The Emperor's New Mind.

In Shadows of the Mind, Penrose tries to clarify what he sees as the physicist's or mathematician's fundamental view of existence, in particular the relationship between the physical world, the mental world and the Platonic world of ideas in which mathematicians and physicists work.

But to no avail. The criticisms continue unabated. Our hero decides to write another book. This time he will invite critics to comment on his ideas and then respond to their points, and the whole package will be published together. Now read on...

The Large, the Small and the Human Mind is the third episode in the saga, and is considerably shorter than the previous two. The large of the title is the physics of the Universe. The small is quantum physics. The human mind is . . . well, that is precisely the question Penrose wants to answer. What exactly is the human mind? What gives rise to intelligent behaviour and to our perceived free will and sense of consciousness? He believes the answers to questions about the mind can be found in a future marriage between the physics of the large and of the small.

It is a bold suggestion, perhaps just wild enough to be near the truth. Then again, I haven't sufficient familiarity with big-bang cosmology or quantum physics to follow all Penrose's arguments in detail, let alone fling various notions around with the seeming abandon of a master such as Penrose, so I cannot confidently judge how likely he is to be correct. And I assume the same is true of most of his readers.

But that doesn't matter. What all three books present is science in the making. For the most part, the stuff that makes its way into science books is the stuff that survives. The mistaken ideas are simply forgotten. The result is that nonscientists are presented with a highly misleading view of science and of the way scientists work. 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.

Of course, from a scientific point of view, the fundamental question is whether or not the argument Penrose presents turns out to be right. But I believe the real value of his books, written so that a general audience can follow the gist of the argument, if not the detail, lies in the fact that he is doing in public what most scientists generally do in private.

Author

Keith Devlin is Dean of the School of Science at Saint Mary's College of California and a senior researcher at Stanford University's Center for the Study of Language and Information.

Further Reading

The Large,The Small and the Human Mind Roger Penrose,Cambridge University Press £14.95,ISBN 0 521 56330 5.