The Fabric of Reality: The Science of Parallel Universes--and Its Implications Paperback – August 1, 1998

The book was published in 1997, and a lot has happened since then. Yet the foundations retain their permanence, and David Deutsch's captivating writing is as fresh as ever. Despite the availability of newer books, for the layman/woman, now almost 10 years later, I would still rank this book at the top. There is a lot in the book; and yet, the ideas are presented in a clear and engaging way. The author is a pioneer, a giant in modern physics; he was and is a driving force in new discoveries in the subject. Yet he has his personal way of explaining physical reality. His view is not shared by all scientists, one should admit. However, there is agreement about the scientific conclusions. The first chapter in the book stresses *explanation*, our understanding of the reason for things. There are other views of science, e.g., instrumentalism: predicting the outcome of experiments.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.

I love David Deutsch's honesty. I teach physics at a small university, and I know I've been guilty of hesitating and couching my words so as to not seem crazy, or to not upset the sensibility of others. But if we're to make progress, we need to be more honest with what we know, and counter those who don't know but should.If you fail to move forward with an understanding of the multiverse in any form, I doubt we'll see the next big breakthroughs from you. That's okay in the larger sense. Many people with a lesser understanding will still make worthwhile contributions in other needed areas. And most don't need to know that our planet is round to make it home. And we can still refer to the sun setting, even if we know it's not; however, even if you don't know this, I suspect you might still make it through life largely unaffected by that failing. . . And it is a failing. And not just yours. It's my failing too. I don't know the answers. I don't know anyone who does. However, I suspect Deutsch's understanding will be far ahead of mine in most times future to now. Which is why I look forward to anything he writes. If you haven't considered also getting his more recent book, The Beginning of Infinity, do.In The Fabric of Reality you will confront the best of the big picture that humans have been assembling for centuries, but which most still can't accept. What can be expected to be known of biological evolution, even to the level of a layman's appreciation, is grasped by only a minority (if you believe in biological evolution with a guiding hand from a god, then you're in that majority who simply don't understand evolution). But I feel comforted to have my closet friends all accept some form of biological evolution, even if we disagree over the details. Quantum physics, however, has an even smaller minority who are willing to face it on its terms, even if we consider only those who do largely accept evolution. Instead we get silliness like the Copenhagen view of Bohr and Heisenberg, or silliness like the wishy-washy view of those belonging to the "shut up and calculate" school. . . Whatever the reason for this (and an important appreciation of where the answer will come from is found in Deutsch's lastest book), read this book from Deutsch, read his latest book (The Beginning of Infinity), if you want to think about these ideas seriously.