Walker starts out with a crash course on the history of science, leading to a lively discussion of Quantum Mechanics that culminates with Von Neumann's proof that consciousness determines reality and with John Bell's proof that everything is connected with everything else. At that point Walker argues that Physics itself proves that Physics is incomplete, in that it does not have a theory of consciousness even if physical reality depends on conscious observers.

Walker argues in favor of a completely new theory to study consciousness, the same way that Newton had to introduce new quantities and new formulas to explain gravitation and Faraday and Maxwell had to introduce new quantities and new formulas to explain electromagnetism.

Walker views consciousness as a different domain of discourse from matter, but, at the same time, recognizes that it is affected by matter: therefore, there must be a way that consciousness and the material world can interact. In particular, the nature of consciousness must be such that it is directly related to events in the brain. The foundations of Walker's Physics of consciousness are two postulates: 1. Consciousness is real and nonphysical; and 2. Physical reality is connected to consciousness by a physically fundamental quantity.

There are several ways that consciousness can be coupled with the material world: space, time, one of the four forces of nature, a particle, the wave function of Schroedinger's equation or... everything. Walker examines each of them and proves tha only the wave function can do the job. That is where the link between mind and brain is to be found.

Walker introduces new quantities that are: the "consciousness field capacity" (the information available in the mind at any point in time) and the "consciousness channel capacity" (the rate at which information flows through consciousness). He estimates the value of the former at two million bits of information, and the value of the latter at 50 million bits of information per second.

Walker believes that the quantum tunneling effect that allows neurons to trigger distant neurons satisfies both postulates and matches those numbers. After all, the synapses are the places where neurons communicate and therefore "thinking" occurs. He can even write the equation for consciousness: the number of electrons that, thanks to the tunneling effect, manage to connect two active synapses. The set of potentialities of all the particles in the brain create consciousness.

As a result, the observer of Quantum Physics turns out to be a quantum system herself.

Walker explains why melanin (a substance that absorbs radiation and is therefore known to help the skin get suntanned) is present in the brain. Melanin is needed to regulate consciousness (the multitude of tunneling electrons) so that it does not get out of control. We would not be able to stay awake 16 hours a day if we had no melanin.

Consciousness is the set of potentialities created by the tunneling effect across the brain. But only a portion of that set becomes reality, as only some potentialities are realized when the wave function collapses at the synapsis. Walker uses that subset to define another mental quantity: "will". Our will is distinct from our consciousness in that our consciousness contains all the possibilities, whereas our will is only what actually happens (what the body actually does).

As a consequence of quantum interconnectedness, Walker also argues that all minds share some mental activity.

Following the Hungarian physicist Eugene Wigner, Walker proposes to add a term to Schroedinger's equation that would make it nonlinear and that would explain what causes the collapse of the wave: a measurement of information. This term, that basically expresses the transfer of information that takes place with the wave's collapse, would disappear once the measurement is performed. Basically, this term would signal the presence of the observer. By introducing the same "information term" in Dirac's equation, Walker derives another possible interpretation: reality is consciousness observing itself. Dirac's equation becomes simply the equation of an observer observing.

Walker also believes in a close connection between space and probability. He interprets Einstein's four-dimensional space-time as time plus an ordering of events that were probable but did not happen (something that we call "space"). The only thing that exists, ultimately, is the observer, who consciously experiences her complement. The sequence of conscious experiences is time, and the set of possible events is space. The universe is the observer observing.

God is the collective will of all observers. Their collective will is what creates and sustains the universe.

The book is a fascinating read, although it is riddled with too many utobiographic episodes (about a girlfriend who died) that add nothing to the scientific discussion, and with a mystical ending that will interest only the least educated new-age crowd.

Walker's own theory (that the quantum tunneling effect is what I feel when I think of myself) lacks both empirical evidence and plausibility. He makes a case that consciousness is relevant to Quantum Physics but not necessarily that Quantum Physics is relevant to consciousness. Until he produces some evidence, his theory is mainly speculation, no matter how wonderfully written.