his book is a collection of 13 tightly-integrated articles by H.P. Stapp, one of the most innovative physicists today studying the possible connections between quantum mechanics and consciousness. Even though some of the articles are now almost 15 years old, their ideas are still cutting-edge, and give a good overall view of the field of quantum consciousness from Stapp's point of view. Stapp is one of the few (David Chalmers is another) who recognizes that consciousness is not just some illusion to be explained away as an emergent property of neurons firing. Such ultra-reductionistic views, expounded by Dennett and many others, overlook something that is a self-evident part of our existence: consciousness, unique among all physical phenomena, creates a privileged frame of reference--namely, the point of view of the observer.

That is, of course, not to say that there is, or even should be, a field of quantum consciousness. Quantum mechanics theorizes that subatomic particles can exist in an entangled state, in which two particles intimately share the same quantum variable, despite being separated from each other in space. It also theorizes that a particle can have two states simultaneously, for example, "up" and "down" spin states, or more popularly, "alive" and "dead" states for Schrödinger's famous cat. When such a particle interacts with matter, as during a measurement or an observation, it can only do so as one state or the other, and so it is forced to choose one at random. This is known as "wavefunction collapse".

Both entangled states and superposed states have received ample experimental evidence. However, some physicists, including Penrose, Hameroff, Stapp, and others, have taken the ideas further, and postulate that an "observation" or "measurement" implies an "observer" or "measurer", i.e. a conscious observer. This has profound implications for our understanding of the mind. But is it true? My understanding is that most mainstream physicists suspect that it is not. A need for an observer has uncomfortable implications about the universe as a whole. If observing something is necessary for it to exist, we would either have to posit some supernatural being who observed the creation of every atom in the universe, or accept that, except for the minute part that we can see, the universe does not, in fact, actually exist, except perhaps as an undifferentiated wavefunction.

The articles fit together admirably as book chapters. Each of the articles is written in a style readily accessible to a layman who has a little physics background. There is a minimum of scientific jargon and no mathematics. However, Stapp's book is by no means just another "popularization" book. It is a serious exposition of Stapp's ideas, along with a healthy dose of philosophizing. Stapp quotes liberally from philosopher William James, widely regarded as the founder of modern psychology, and discusses the philosophical implications of quantum mechanics at length.

In chapter 3, where Stapp describes the Copenhagen interpretation of quantum mechanics, he also includes two pages of comments from physicist Werner Heisenberg. In these comments, Heisenberg chides Stapp for having "too much confidence in the language." By this, I think Heisenberg means that the experimental should have primacy in physics, and that philosophizing about whether quantum mechanics is a true or complete description of reality is somewhat irrelevant, because it risks taking Stapp along the path of the Dark Side toward philosophy, where so many great minds have gotten lost in the past. I think Heisenberg makes an excellent point here. The Copenhagen interpretation is really a form of Berkeleyan material idealism, in which we admit the impossibility of understanding the real nature of particles. It is a recognition that the quantum world is so far removed from our everyday experience that attempts to describe it with language cannot be trusted. We must simply use equations based on the experimental evidence as our mental model; otherwise we may see paradoxes where none exist. For instance, it is likely that wave-particle duality is not a real phenomenon, but simply an artifact of our brain's tendency to mix two incompatible theories: the simpler, more intuitive "particle" theory, and quantum mechanics, which views particles not as point-like entities but as delocalized wavelet-like phenomena in space.

If one accepts the Copenhagen interpretation, it follows that philosophizing about these aspects of physics is largely a waste of time. The main purpose of philosophy is to ask questions and give us a variety of mutually-incompatible frameworks in which to conceptualize ideas. It's not within the realm of philosophy, as intellectually stimulating as it may be, to provide answers. Thus, Stapp is forced to spend some time distinguishing Heisenberg's Copenhagen interpretation, which is the dominant one in physics, from his own "quantum ontology."

In the chapter "Mind and Matter", Stapp describes his theory of the brain. Stapp views the brain as a network, similar in some ways to the simple models of Hopfield. Stapp's model is reminiscent of the very earliest neural network models from the 1960s, which described patterns as distinct cohesive waves propagating from one side of the brain to the other. In Stapp's model, ideas corresponding to different quantum states float around as discrete entities until they are selected by a sort of Edelman-like neural Darwinism, leaving only those ideas that correspond with the observation of the quantum state. To re-state more simply, Stapp believes that superposed quantum states decohere in the brain. This point of view is far more radical than even Penrose and Hameroff dared to suggest. For example, on page 117 he states:

[T]he conscious act is functionally equivalent at the level of perceptible changes to its image in the physical world represented by quantum theory. ... it correctly represents the functional efficiency of the conscious creative act both in the world of conscious experience and in the physical world represented by quantum theory.

This means that Stapp believes that consciousness is causally linked to quantum changes in the environment, and that perception can directly produce changes in the outside world. This is a very radical viewpoint.

How does a wavefunction collapse produce consciousness? Penrose, in his book The Emperor's New Mind and elsewhere, has speculated about perturbations of spacetime geometry, spin networks, and even gravity. Penrose insightfully recognized that an explanation of time is also needed to understand consciousness. He wrote:

The self-collapse [of the wave function], irreversible in time, creates an instantaneous `now' event. Sequences of such events create a flow of time, and consciousness.

This is all very interesting, and it has a great Star Trek: The Next Generation feel about it, but it's not a compelling explanation of consciousness. Just what is a "now event" exactly, and just how does a flow of time create consciousness? More fundamentally, why do Stapp and Penrose believe that a conscious observer is necessary to produce a wavefunction collapse? Both physicists take this point as axiomatic, and it is essential for their theories. To some people, however, the idea that an observation implies an observer sounds very much like the same kind of flawed logic that led to creationism. Crucial facts like what constitutes an observation need to be nailed down before we can say whether quantum mechanics really has anything to do with consciousness. As scientists customarily say, "more research is needed."

(For more discussion of these ideas, see my article Quantum Consciousness, Quantum Information, and Subjectivity ).