A public talk sponsored by
The Department of Physics at the University of Hong Kong.

Thursday, April 6, at 5:30 p.m. in Lecture Theatre T3 of the Meng Wah Complex.

Note: In addition to the background information below, further details of the talk (with photographs) and a more detailed critical discussion on the subject of science and consciousness can be found at the following website:

Science and the Mind: critical comments

Background Information

Science has made enormous strides, particularly this century, in furthering our knowledge of the universe, from its smallest corners (the world of fundamental particles and quarks) to its largest realms (the world of supernovae, black holes and galaxies). This journey has not been easy and there are still a few inconsistencies in our theories, especially in trying to reconcile the microscopic world, where quantum mechanics rules with a firm - but curiously indeterminate - hand, to the macroscopic world of planets and stars, where gravity appears to have the upper hand.

The quantum-mechanical theories of Erwin Schrödinger, Werner Heisenberg and others seem to be at odds with Albert Einstein's theory of relativity in whether or not we enjoy free will. Quantum mechanics insists that the future is unpredictable, while in relativity space fuses with time to create a four-dimensional structure in which past, future and present are merely relative terms in a world which reveals itself through our consciousness as a one-directional flow in time - an illusion, as Einstein always insisted.

Why the mind should trick us in this way has always been a puzzle; a puzzle that has occupied - and also eluded - the minds of the greatest philosophers from the time of the ancient Greeks to the present day. Now, it appears, it is the turn of the physicists to apply their minds to this thorny issue. Some of today's greatest physicists are now actively working on theories that they hope will enable us to break through one of the last frontiers in our attempt to understand the world - how the mind gives rise to consciousness.

At the forefront of this race to conquer the mind is Roger Penrose, a physicist at Oxford University who in 1988 shared the prestigious Wolf Prize in Physics with his equally famous counterpart at Cambridge University, Stephen Hawking, for their joint contributions to our understanding of the universe. Penrose has proposed that the mysteries of the mind must be related to the mysteries of quantum mechanics and central to his theory is the claim that no deterministic, rule-based system - such as classical physics, computer science or neuroscience - can account for the mind's creative powers and ability to ascertain truth.

In 1989, Penrose wrote the best-seller The Emperor's New Mind: Concerning Computers, Minds and the Laws of Physics (Oxford University Press), a marvellous survey of modern physics, the book was also a provocative reflection on the human mind and offered a new perspective on the scientific landscape together with a visionary glimpse of the possible future of science. More importantly, as far as the mind is concerned, it launched a vigorous attack on the claim of artificial intelligence proponents that computers can replicate all human attributes, including consciousness. In the more recent sequel, Shadows of the Mind: A Search for the Missing Science of Consciousness (Oxford University Press, 1994), Penrose offers another exhilarating look at modern science as he mounts an even more powerful attack on artificial intelligence. But, perhaps more importantly, he points the way to a new science, one that may eventually explain the physical basis of the mind.

Penrose provides powerful arguments to support his conclusion that there is something in the conscious activity of the brain that transcends computation - and for which there is no explanation in terms of present-day science. To illuminate what he believes this 'something' might be, and to suggest where a new physics must proceed so that we may understand it, Penrose cuts a wide swathe through modern science, providing penetrating looks at everything from Turing computability and Godel's theorem, via Schrödinger's cat and the Elitzur-Vaidman bomb-testing problem, to detailed cell biology. Of particular interest is Penrose's examination of quantum mechanics, which introduces some exciting new ideas, especially concerning quantum entanglement, the mysterious interface where classical and quantum physics meet.

Penrose argues that microtubules, minute substructures lying deep within the brain's neurons, rather than neurons themselves may be the basic units of the brain, and that it is within them that the collective quantum effects necessary for consciousness reside.

For physics to accommodate something that is as foreign to our current physical picture as the phenomenon of consciousness, we must expect a profound change - one that alters the very underpinnings of our philosophical viewpoint as to the nature of reality. Science and Mind will provide an illuminating look at where these changes may take place and what our future understanding of the world may be. In doing so, we may learn more about what we are, how we think and what makes us human.

Abstract of Talk

The methods of science have proved to be extraordinarily successful in describing the physical behaviour of the world. This success depends, to a large extent, upon the remarkably close accord between physical behaviour and certain precise mathematical laws. This mysterious relationship is related to a second mystery: how is it that our minds are able to perceive this world of "ideal" mathematical concepts? The famous "incompleteness" theorem of Gödel (as will be illustrated by a particularly striking but elementary example of it known as Goodstein's theorem) tells us that human mathematical understanding cannot be encapsulated by any trustable computational procedure. This strongly indicates that there is something involved in human understanding that lies beyond the actions of any computer. Understanding being a particular manifestation of human consciousness, this suggests that it is conscious mentality that lies outside computational activity.

Accordingly, if physical action in the brain is to be responsible for human mentality, then something of a non-computable character must reside in Nature's laws. This brings us to a third mystery: how can a physical object, namely a living human brain, actually evoke conscious mentality? Any genuine progress towards understanding this mystery will, in my opinion, require addressing the two other mysteries also. I shall argue that the natural place to expect the required non-computability is in an as-yet undiscovered theory bridging the small scale physics of quantum theory to the large-scale space-time principles of Einstein's general relativity. (The FELIX space experiment may be able to test the requirements for such a new theory in the not-too-distant future. Moreover, there are other experiments that could test quantum non-locality in human perception.) Finally, I suggest that the most likely place for this new physics to be relevant to brain action is in the network of neuronal microtubules.

Biographical Information

Roger Penrose, a professor of mathematics at the University of Oxford in England, pursues an active interest in recreational mathematics which he shared with his father. While most of his work pertains to relativity theory and quantum physics, he is fascinated with a field of geometry known as tessellation, the covering of a surface with tiles of prescribed shapes.

Penrose received his PhD at Cambridge in algebraic geometry. While there, he began playing around with what appears to be a somewhat frivolous geometrical puzzle. He wanted to cover a flat surface with tiles so that there were no gaps and no overlaps. There are several shapes hat will do the job, regular triangles, rectangles, hexagons, and so forth. Or it can be done with combinations of shapes, resulting in a pattern that repeats regularly. Penrose began to work on the problem of whether a set of shapes could be found which would tile a surface but without generating a repeating pattern (known as quasi-symmetry). It turned out this was a problem that couldn't be solved computationally. So, armed with only a notebook and pencil, Penrose set about developing sets of tiles that produce 'quasi-periodic' patterns; at first glance the pattern seems to repeat regularly, but on closer examination you find it is not quite so.

Eventually Penrose found a solution to the problem but it required many thousands of different shapes. After years of research and careful study, he successfully reduced the number to six and later down to an incredible two. These tiles are particularly intriguing to play with because you have to take into account more than just the tile next door to decide how pieces fit together. Anyone can have a go at this problem. Professor Penrose has designed a puzzle using this tiling concept which is now available in commercial stores. The puzzle consists of bird-shaped pieces which are kept in play on a gameboard built into the box. Using just the two shapes, small and large birds, the goal is to completely cover the playing surface. Sounds easy? It's not, and there is only one solution. At higher levels you substitute a rogue dog for a large bird and the solutions change. By the time you have five dogs substituted you'll have gone through potentially 23 different solutions to just one puzzle.

While this may all sound rather far removed from life in the real world, it turns out that some chemical substances will form crystals in a quasi-periodic manner. Professor Penrose tells of a striking demonstration of the benefits of pure research - a French company has recently found a very practical application for substances that form these quasi-crystals: they make excellent non-scratch coating for frying pans.

Penrose was raised in a family with strong mathematical interests: his mother was a doctor, his father, a medical geneticist, used math in his work as well as his recreation, one brother is a mathematician, another was ten times British chess champion. Roger originally was more attracted to medicine than math, but when forced to choose between biology and math because of inflexible school scheduling, he was not willing to give up the mathematics.

Roger and his father are the creators of the famous Penrose staircase and the impossible triangle known as the tribar. Both of these impossible figures were used in the work of Dutch graphic artist Maurits Cornelis Escher to create structures such as a waterfall where the water appears to flow uphill and a building with an impossible staircase which rises or falls endlessly yet returns to the same level.