The Fabric of Reality: The Science of Parallel Universes - and Its Implications

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 see this book as the ultimate guide to cake baking. It is the very thing the title suggests ~The FABRIC of Reality~. As a famous saying goes, "To bake a cake from scratch first you create the universe" This book identifies the absolute basic ideas that define our understanding of what our senses tell us. Regardless of what you think of his theory of the multiverse or even his views on quantum physics you must admire the way he challenges us to look at the things we believe in their most basic form. He says if you kick a stone and you feel it hurt your foot then you must assume it is real. All our lifetime beliefs must stem from this simple observation. To me DD has opened up my eyes to see the world and after reading this book my mind was forced to make adjustments in the way I come to accept things as fact. He goes to the very heart of what not only what the fabric of the universe is but during the explaination forced me to see what the fabric of my own surroudings is and how I should decide what to believe in. I must highly recommend this book as required reading to anyone who has ever decided to belive in something just because someone else said it was true (hint - religous writings) without offering the rock kicking experiment to prove it.

I would love to see many-worlds shown superior to all available alternatives, but this book did not make the case. The chapter on epistemology is excellent. He concludes that a successful theory must have explanatory power and must satisfy evidence that refutes all prior theories. He does a good but incomplete job of illustrating the explanatory power of many-worlds, failing to show how many-worlds explains the EPR results. Unfortunately he ignores all competent existing theories. Indeterminism and wavefunction collapse are not required by QM. They are merely interpretations. Wavefunction collapse in particular is not required to explain the double-slit results because the virtual particles (another interpretation) that constitute the wavefunction are not observable and have no relation to the new entity that results from a "measurement" interaction. The EPR experiments assert that "hidden variables" havc been eliminated, but indeterminacy is still not proven. Deutsch rightfully proclaims many-worlds superior to one interpretation of QM, based solely on the double-slit results, but he fails to mention alternatives. The most compelling evidence is the idea that a quantum computer could make computations requiring >10^500 parallel universes. IF such a computation is performed, it may be difficult to explain in any other way, but it has not been done and the obstacles may be fundamental. He asserts that all worlds in the multiverse must follow the same physical laws. There are many more worlds out there that fit in his philosophy. We know our particular laws result from post-Big-Bang broken symmetries and that event itself was not a pristine Perfect Form. What does Deutsch mean by "laws of physics"? Is his interpretation that there are many multiverses? I had great hopes for the chapter on time, but his writing style is sometimes impenetrable and it came across as hand-waving. If Richard Feynman liked many-worlds, it must be right. Deutsch should try again, in collaboration with a scientifically literate writer.

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.

This is philosophy from a scientist's point of view: Understanding is useful to a scientist, therefore science is about understanding. A particular interpretation is the most elegant, therefore it represents reality. Such and such ideas do not stand to scientific scrutiny, therefore they "collapse". Let's see: If science is about understanding, it is rather strange that it is so difficult to define what understanding is. The book has an entire page devoted to this supposedly fundamental matter, stating, more or less, that scientists know an explanation when they see one. One is left wandering what will happen when in the future scientists discover a better theory or a better interpretation of a given theory. Presumably one reality will then be substituted by another. Now, life's DNA codifies knowledge about its environment even though clearly no understanding is present. After all a sparrow does not understand aerodynamics and even so knows how to fly. In the same way science can codify a lot of knowledge about the environment without the need to place understanding at its center. "An explanation centered theory of knowledge" is in fact not required, as evolution itself proves. Instrumentalism states the more reasonable view that science is basically an instrument for controlling our environment and that understanding is an important psychological by-product. What scientists visualize does not necessarily reflect reality even though it makes it easier to understand it. Deutsch attacks a trivialized view of instrumentalism according to which the only value of science is in its predictive power. A big part of the book discusses "the problem of induction", i.e. what justifies science. I fail to see why this is a big problem - it is not explained in the book. I suppose that most scientists, if asked, would say that what justifies science is the fact that it works. Now the question about reality. Until recently, scientists have described many surprising things about what they call reality, but these happen in microscopic scale, or in a huge scale, or at huge speeds, or in really ancient times. So science adds to the meaning of the word reality without contradicting it. Deutsch oversteps the bounds when he describes the multiverse theory (which I see not as theory but as an interpretation of the theory of quantum mechanics). According to this view, reality is composed of a multiplicity of universes where any phenomenon allowed by quantum theory does happen albeit in a different proportion of number of universes. I am not sure if the readers of the book see how fantastic this view is: When you switch on a light you actually give rise to a zillion universes. In many universes Hitler has won the war, and in many others the statue of liberty suddenly disappeared from New York harbor and materialized itself in the middle of Tiananmen square. It gets worse. In many universes the devil exists! Yes, he appears in his horned majesty and does a lot a mischief. Televangelists will be very happy when they find out that modern science accepts the reality of Satan. A scientist may respond that the relative number of these universes is extremely small, but a televangelist may claim that ours is one of these universes and that Satan will shortly make himself visible to all, including to quantum physicists. If the multiverse is real then he may be right! The wave-matter interpretation of quantum mechanics makes much more sense here: it posits only one universe, ours, where for all practical purposes the probability of the appearance of the devil computes to zero. So, clearly, the multiverse is not real because it contradicts the meaningful use of the word "real". Scientists can discuss what is real and what not, but they may not change the meaning of the word itself. Deutsch is pushed into this error in many other instances. For example he flatly states "we do not experience time flowing, or passing". I can assure him that I do in fact experience time as flowing or passing. He goes on to discuss "the common-sense theory of time" and doesn't notice that common people do not have a theory of time, they only have a sense of time, and this is an unmovable given. Scientists can make use of the word time as an instrument in their work, but to come back and state that people's sense of time is "nonsense" is nonsense. He states that "free will is an illusion" because it contradicts the space-time theory. It never occurs to him that his interpretation of space-time theory may be the illusion. The book is so arrogant that it can be irritating. It states "What is life? Darwin has answered that question." In fact, Darwin has done no such thing. He has only described the mechanism that gives rise to the diversity and complexity of life forms. Nobody yet knows how life came into being. What I found most troublesome in this book is the implicit belief that only the scientific mode of thought is justified when discussing any matter, even philosophical questions. For example he criticizes solipsism by showing that if we take solipsism seriously (i.e. apply scientific mind-set to it) a solipsist will not be able to withstand scientific scrutiny and therefore solipsism "collapses". Now, if a solipsist would apply the solipsistic mind-set to science, then he would be able to show that science "collapses". At bottom many of Deutsch's arguments are circular and go like this: only the scientific mode of reasoning is valid, therefore all non-scientific modes of reasoning are invalid. In conclusion, this is not a book about the fabric of reality, but is rather a book about the fabric of scientific thought. As such it is a useful book, because it shows where the limits of scientific thought lie, as well as the absurdities that happen when it is applied to the wrong kind of questions.

One of my highest recommended books of all time

Mind bending...

...instead of relying on the reductionist creed “it doesn’t matter why - the predictions agree with experiment, and that should be enough”. That’s what my quantum physics professor said when I pushed on interpreting the results of the double slit experiment. My disappointment with that answer led me to abandon physics. Had Deutsch been my professor, I would have stayed in it. Back to the book: I found the sections on epistemology and quantum computation to be less elucidating than the stunningly simple logic that he uses to justify the many-world interpretation of quantum mechanics, but it’s all fascinating. The connections between seemingly disparate domains (QM, theory of computation, genetics, and epistemology) are novel and reminiscent of Godel, Escher, Bach. Chapter 2 is a must-read and the rest of the book is highly worthwhile for the patient reader.

Few people want to know the reality. David Deutsch helps you understand the world in which you live

El libro es interesante pero está escrito para especialistas, al estilo de artículos académicos. No es divulgación, deberían avisarlo. Para los que no somos físicos es un auténtico ladrillo y eso que estoy acostumbrada a leer textos densos de forma habitual. Infumable.

profound

You can't consider yourself an honest thinker if you haven't read this book - or some equally deep one (if you manage to find it).

Great