The Fabric of Reality: Towards a Theory of Everything (Paperback)

I am not a trained scientist, simple a well informed non-specialist with an interest in these areas, and I would have to say that this is the best written book of its type I have come across. It deals with extremely deep concepts across an enormous range of different but related areas of study, and I found myself at times almost shocked at the superb skill with which the author is able to deliver new concepts and arguments so cleanly and simply. The chapter that deals with quantum theory and the many-worlds hypothesis alone stands out as a masterpiece of elegance and simplicity when compared with many other works that attempt to deal with this issue.

Rather than delighting and wallowing in the apparent paradoxes that quantum theory implies for the macroscopic world (as so many authors do), Deutsch simply points out that irrespective of our inability to understand and resolve those paradoxes, the conclusions at least are clear and unarguable, and this is where he starts the real work of philosophical integration that is the books theme.

The rate at which new ideas in this book are delivered can leave one stunned at times, and I must recommend this book without any hesitation at all.

The author's view on quantum theory is based his idea about parallel universes. While fascination, the reader should be aware that there are alternative theories for explaining quantum phenomena. An important concept in quantum theory and quantum computation is "decoherence", and it is explained (ch 9) in terms of different (parallel) universes. In ch 9 about quantum computers, it might have been only fair to mention that there are such other current views on decoherence; but this is a minor complaint.

Presentation: I love that each chapter concludes with a section on terminology and a summary.

As a subject theoretical computer science started with Alan Turing and John von Neumann in the 1940ties: Classical computation follows the model of Turing,-- strings of bits, i.e., 0s and 1s; and a mathematical model which is now called the Turing machine.

Instead of bits, why not two-level quantum systems, e.g., models built from electrons or photons? Such an analogues model for computation based on two-level quantum systems, and a quantum version of Turing's machine was suggested in the 1980ties by R.P. Feynman. The form it now has owes much to the author himself, David Deutsch. But it wasn't until Peter Shor's qubit-factoring algorithm in the late 1990ties (not covered in the book) that the subject really took off, and really caught the attention of the mainstream science community, and of the general public: The 'unbreakable' codes might be breakable after all !

That there is a polynomial factoring algorithm, as Shor showed, shook up the encryption community, for obvious reasons, and created headlines in the news. Ideas in the quantum realm, and not part of classical thinking, include superposition of (quantum) states, the EPR paradox (1935), and (quantum) coherence. Although these concepts are at the foundation of quantum theory, they make a drastic change in our whole theoretical framework of computation: Now one passes from the familiar classical notion of bit-registers to that of qubit-registers, and the laws of quantum mechanics take over. Mathematical physicists and computer scientists must revisit the old masters: Bohr, Einstein, Heisenberg, Pauli, and Dirac. In passing from logic gates to quantum gates (unitary matrices), the concept of switching-networks from traditional computer science now changes drastically. The changes introduce brand new scientific challenges, and new truly exciting opportunities. I believe that this book does justice to this, and that it is still a fascinating and thought provoking invitation to some of the most intriguing trends in modern physics.
Review by Palle Jorgensen, July 2005.

The individual constituents of the world-view are not really new (as the book's dedication to sir Karl, Hugh Everett, Alan Turing and Richard Dawkins clearly indicates); but as a synthesis it makes some unexpected connections between them. To name one example: for a computer scientist such as myself, the statement that the Church-Turing hypothesis should be regarded as a physical fact had quite a goggle-factor!

From the beginning, with its introduction to the two-slit experiment, Deutsch firmly avoids the usual Copenhagen-inspired descriptions, instead brazenly arguing that the results can support no other interpretation than the many-worlds. The descriptions of Popper's epistemology and Dawkins' selfish-gene evolution are less revolutionary, but integrate nicely. Applying a computational perspective on physical reality (or a physical perspective on computation!) is not unique to Deutsch, but making such far-ranging connections to epistemology and evolution is, as far as I know.

To balance the critique, arguing from virtual reality seem a bit hypish (to coin a word); although one may suppose that Gedankenexperimenten should keep up with current concepts and technologies. Some of the conclusions could have benefited from more discussion and analysis (what makes parallel universes different from temporally sequential ones? what unifies them? is there a problem of induction here?).

This is not a book one finishes in one sitting; neither is it one to be read only once. I do not think that one needs be familiar with QM, epistemology, computation or evolution even at a pop-science level to enjoy reading this book; but knowing the Copenhagen interpretation should certainly make you sit up straight and pay attention -- otherwise, you may simply be convinced that Deutsch's explanation is the only one possible!