A Reading Guide to David Deutsch: Explanations and the Multiverse

By David Deutsch:

  • The Fabric of Reality: Chapters 1, 2, 3, 4, 8, 9 pp. 200-207, and 11
  • The Beginning of Infinity: Chapter 3

Supplementary Reading:

  • Philosophy and the Real World (a.k.a. Karl Popper) by Bryan Magee: Chapters 1-5 (suggest reading after chapter 3 of The Fabric of Reality)
  • The Selfish Gene by Richard Dawkins: Chapters 2-4 (suggest reading before chapter 8 of The Fabric of Reality)

(310 pages total)

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“They’re ambitious titles, true, but they’re ambitious books—in fact, among the most ambitious works of non-fiction I have read, in that their aim is no less than an explanation of all reality. But these are not Brian Greene- or Stephen Hawking-style rundowns of recent discoveries in theoretical physics. Rather, they are treatises that weave together not just physics and astronomy but biology, mathematics, computer science, political science, psychology, philosophy, aesthetics and—most important for Deutsch—epistemology, among other fields, in fashioning a profound new view of the world and the universe. They are guaranteed to be either provocative or life-changing, depending on how seriously you take their ideas. Either way, they earn their colossal confidence.” –Nathaniel Stein, The New Yorker

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Professional physicist and semi-pro philosopher David Deutsch’s works—most of The Fabric of Reality (1997) and a few parts of The Beginning of Infinity (2011)—have completely transformed my view of life and the universe, at a comparable level to probably only two other works I’ve encountered, Richard Dawkins’ The Selfish Gene (1976) and part 3 of Derek Parfit’s Reasons and Persons (1984). (Go Oxford!) I feel that anyone who regularly wrestles with the big ideas of science and/or philosophy should have Deutsch on their plate.

I would like to simply recommend that you read his books, starting with the first, but I’m afraid if I did that many would give up before they got to the best parts—especially those more used to reading popular science than philosophy. Large portions of his text can be maddening. He is often not clear about what question he is answering, or why he is answering it. And his organization often leaves one feeling that he is throwing things out as they pop into his head, rather than carefully structuring one idea to follow from another.

So I decided to create a reading guide to help people through, so I can share the gospel of these ideas which have so altered my thinking. There are two strands of his work in particular that I find most interesting: 1) his explanation of the multiverse interpretation of quantum mechanics, and 2) his ideas about knowledge itself (a.k.a. epistemology), which include Karl Popper’s philosophy of science (a critique of induction), an understanding of the role of explanation (as opposed to mere prediction) in knowledge creation, and the significance of knowledge and knowledge creating organisms in the universe. This last one comes as a contrast to a prevailing scientific-humanist idea that insists on seeing people as a vanishingly insignificant part of a vast universe, which, while an admirable attempt to demote our lingering religious conception of ourselves as the center of the universe, is nonetheless according to Deutsch factually incorrect on an objective long view (see chapter 3 of The Beginning of Infinity; though I put it last on the reading lists, it could easily be the first thing you read by him).

To help those with more specialized interest, I’ve split the reading guide above into two, a scientific one and a philosophical one, that roughly correspond to these two strands. In particular, anyone interested mainly in popular science, without much experience (or interest) in reading philosophy, should definitely take on the science reading list, as Deutsch is currently the best popularizer and chief evangelist of the multiverse view, and the idea is severely under-served in both professional and popular physics. Of course, I’d say that they are best read together, as in the reading list above, but you are welcome to take any path you like.

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1) Science: Understanding the Multiverse

The Fabric of Reality:

  • Chapter 2
  • Chapter 4 pp. 73-80, 86-90, 93
  • Chapter 8 pp. 187-192
  • Chapter 9 pp. 200-207
  • Chapter 11

(77 pages total)

The only thing I’ve ever felt I understood about quantum mechanics is the multiverse interpretation, as explained by Deutsch in chapter 2 of The Fabric of Reality. I had encountered attempts at explanations (including other attempts to explain the multiverse) from probably twenty or more different sources in the past (including the modern physics course I took for my science education degree), and the standard line is to just admit that there actually is no explanation for it, it just is. This view is so pervasive that it actually has a respectable name: The Copenhagen Interpretation. Deutsch thinks this is crap. He believes that the interference patterns in the well-known double slit experiment require us to believe that there are an infinite number of other “phantom” photons in parallel universes interfering with the one photon we shoot at the screen in ours, which to us is the “real” photon (scare quotes are used because in fact both types of photon have exactly the same ontological status). He asserts that the multiverse “is the only known explanation of many phenomena and has survived all known experimental tests”, and tags off from his and Popper’s theory of knowledge to insist that we thereby “have no choice but to accept” the implications of the multiverse.

It’s heady stuff, but this chapter, called “Shadows”, is an essential popular science essay, straightforward and clear enough for anyone to understand. It’s one of those things that, in a few short pages of crystal clear explanation, can upend your perception of everything and suddenly lock into place concepts that have been nebulous in your mind for years (much like chapter 2 of The Selfish Gene did for me ten years prior). To be sure, I wouldn’t say that I am certain that the multiverse exists. The idea is about as big a shock to our conception of ourselves and the universe as could be. If it were true, then there would also be an infinite number of “us’s” in these parallel universes as well, made up of all the “phantom” counterparts of the particles that make up our bodies. This is hard to take, but Deutsch believes that this is the only reason the theory is not widely accepted. There is no good objective reason not to accept it. So I’m warming to it. I mostly find the idea compelling because I understand it in a way that I don’t understand other interpretations of quantum mechanics (which in itself isn’t necessarily an argument in its favor, considering my ignorance of the advanced mathematics). Further, finally coming to understand quantum mechanics via the multiverse has allowed me to get a foothold on other discussions of quantum mechanics that don’t even take the multiverse into account.

Chapter 4, “Criteria For Reality”, presents Deutsch’s argument for why we must take the multiverse to be true (i.e., his argument against the wishy-washiness I’m exhibiting toward it) via a compelling comparison to Galileo’s discovery that the earth and the planets revolve around the sun, and the Inquisition’s response to this discovery. He makes a cogent argument that the difficulty people found in accepting this fact in the early 17th century is identical to the difficulty people have of accepting the multiverse now. The section of chapter 8 (“The Significance Of Life”) I mentioned may be difficult going for those not taking the time to learn the epistemology, but it presents a novel idea of how knowledge and randomness would each appear different in the multiverse—in other words, how knowledge could be picked out from a background of randomness in the multiverse—via a comparison of genes and “junk” DNA. He concludes that life and thought, while appearing insignificant in a single universe, “have generated the largest distinctive structures in the multiverse”.

The section of chapter 9 (“Quantum Computers”) I mentioned presents a comparison of classical determinism and chaos theory (a.k.a., the butterfly effect) on the one hand and quantum mechanics and the multiverse on the other, making the essential point that, since reality is not in fact described by classical physics, the butterfly effect in fact does not even exist. Small differences in initial conditions do not amplify or ramify in quantum mechanics, a.k.a., reality.

Chapter 11, “Time: The First Quantum Concept”, will probably be the most interesting to most people after chapter 2, in which time is explained via the multiverse. The first part of this chapter, Deutsch’s refutation of our standard conception of time (the “flow of time”), I consider to be rather poorly written, and I therefore don’t really understand it even after repeated passes at it, but some understanding of what Deutsch thinks of as the wrong way to think about time is necessary to put into context the multiverse theory of time, the right way to think about time. The multiverse theory of time can be encapsulated in Deutsch’s idea that “other times are just special cases of other universes”, and in Deutsch’s imagining of the multiverse as a lattice of static snapshots of individual moments in individual universes.

Those with a sufficient interest in popular science and theories about concrete reality will also probably find Deutsch’s ideas about the significance of people in the universe to be quite interesting, even without wrestling through the more difficult aspects of his epistemology. I found chapter 14 fascinating, though many professional reviewers rated it quite poorly. Tagging off of an idea by Frank Tipler, it’s about the possibility that knowledge-creating organisms descended from humans will be able to put off the end of the universe indefinitely. As I said above, Chapter 3 of The Beginning of Infinity is also excellent, a refutation of the idea common to humanistic popular science that people are insignificant, and of the idea that the earth is a “natural” habitat for people.

And if you do get The Beginning of Infinity, Chapter 11 re-examines his take on the multiverse from a new angle, taking on the use of doppelgängers in science fiction, and the internal consistency of fiction in general, as a way into understanding how parallel universes (would) work in reality. I couldn’t grasp the significance of it when I first read it, before my “eureka” moment with chapter 2 of The Fabric Of Reality, but it all makes sense once you’ve got the fundamentals of the multiverse down. Chapter 12, “A Physicist’s History of Bad Philosophy”, starts out with a nice little dialogue about the truth of the multiverse, and then gives a short history of the interpretations of quantum mechanics, up to page 311. After that is some heavier-going philosophy on Deutsch’s theories about explanation.

Finally, I’ve gathered some other bonus readings in this science and multiverse category here.

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2) Philosophy: Knowledge and its Significance to the Universe

  • The Fabric of Reality: Chapters 1, 2 and 3
  • Philosophy and the Real World: Chapters 1-5
  • The Fabric of Reality: Chapter 4
  • The Selfish Gene: Chapters 2-4
  • The Fabric of Reality: Chapter 8
  • The Beginning of Infinity: Chapter 3

(272 pages total)

Deutsch’s theory of knowledge is actually integral to his understanding of the multiverse, but I found it to be harder work, requiring some supplementary material, dipping into my philosophy dictionaries, and taking notes for me to really get it, which is a style of reading that some people might not be up for. If you are interested though, I think it’s just as rewarding as his explanation of the multiverse.

Chapter 1 of The Fabric of Reality is called “The Theory of Everything”. It states the thesis of the book, and is a good introduction to how he thinks about science and knowledge. I’ll just note that what he takes to be a Theory of Everything is quite different, and much bigger than, the sought-after harmony of relativity and quantum mechanics made famous by Stephen Hawking. Chapter 2 as I said is the introduction to the multiverse, which he uses throughout his work as one of the central examples about the advance of scientific knowledge.

Chapter 3, “Problem-Solving”, explicitly introduces the ideas of Karl Popper, mostly his solution to/evaporation of the problem of induction. I don’t think it does a very good job of it though. This is where my criticism that Deutsch does not always make it clear what he is talking about or why comes into play. Fortunately, at the end of The Fabric of Reality he provides a short list of books he thinks everyone should read, and one of them, Philosophy and the Real World by Bryan Magee, provides exactly what Deutsch lacks, the full context and clear explanation of Popper’s philosophy. (An earlier edition of the book is titled Karl Popper, and this is the name under which Deutsch gives the recommendation, though this edition is much rarer.) The book itself is just over 100 pages, and you need only read 72 of them for present purposes (and they are large type to boot), so this is not an arduous requirement by any stretch, and I found it very rewarding. This is one of the best short introductions to a philosopher I’ve ever read. You are of course welcome to plow on with Deutsch without reading this, but it’s there if you need it.

Chapter 4, “Criteria For Reality”, presents Deutsch’s argument for why we must take the multiverse to be true via a compelling comparison to Galileo’s discovery that the earth and the planets revolve around the sun, and the Inquisition’s response to this discovery. He makes a cogent argument that the difficulty people found in accepting this fact in the early 17th century is identical to the difficulty people have of accepting the multiverse now. (No, you’re not imagining things; I just copy-pasted that summary from the section above. Sorry. I’ll do it again though.) Here we begin to see the heavy kind of work Popper and Deutsch’s ideas about knowledge can do in the real world.

Chapter 8, “The Significance of Life”, which could also be called “The Significance of People”, is an important strand of Deutsch’s ideas about knowledge. People to him are any organisms which create knowledge, whether they evolved on earth or elsewhere. Essential to understanding this though is understanding the replicator theory of evolution, which Deutsch barely explains, and that not very well. It’s no matter though, because this theory was explained spectacularly by Richard Dawkins in The Selfish Gene, and you should not find it frustrating to have to reach for another piece of supplementary material at this point, because this is the one book that absolutely every educated person everywhere should read anyway, no matter who you are or what you are trying to accomplish. It’s not difficult; Dawkins is obsessive about establishing proper context for his ideas and presenting them clearly, even to people with no prior exposure. (And fortunately, it is very popular, so a great many people approaching Deutsch will have already read it.) I’ve made it easy by extracting three essential chapters to understanding replicators and how they relate to life and human beings, chapters 2-4. (These three chapters also largely avoid the politically controversial, though not untrue by any stretch, ideas about genetic influence on/creation of the behavior of organisms.) The chapter on memes, chapter 11, is also highly recommended. It’s the founding document of another wide-reaching theory, and is important to fully understanding Deutsch’s theories of knowledge.

Deutsch’s second book, The Beginning of Infinity, relies a lot on the explanations and conclusions he gave in The Fabric of Reality, but in the service of a new thesis—that progress is unbounded. He attempts to re-explain them in many parts, so that he can move on to his new points, but the re-explanations feel to me even more scattershot than the original explanations. There is one chapter containing some purely new ideas and concepts that I think is essential though. Chapter 3, “The Spark”, seeks to explode two myths that every right thinking progressive science-minded person is meant to believe: the spaceship earth and the principle of mediocrity.

Spaceship earth is the idea that humans can, or were meant to, live in the “womb” of mother earth without using our knowledge to transform it. The principle of mediocrity is, to quote Stephen Hawking as Deutsch does, that humans are “just a chemical scum on the surface of a typical planet that’s in orbit around a typical star that’s on the outskirts of a typical galaxy.” Deutsch’s answer to these two assertions is that 1) “People are significant in the cosmic scheme of things” and 2) “The earth’s biosphere is incapable of supporting human life.” If you want a teleological spin on it, you could say that we are by our very nature knowledge creating organisms, and the universe by creating such organisms thereby “means” for them (us) to transform it. We are (or our emergent properties are) a force of nature in and of ourselves, as much as nuclear fusion and all the rest. As I said above, this chapter could profitably be the first thing you read by Deutsch, so well known are the ideas he is discussing.

You may find it quite interesting after this to go back and read chapter 14 of The Fabric of Reality, “The Ends of the Universe”. I found it fascinating, though many professional reviewers rated it quite poorly. Tagging off of the Omega Point idea by Frank Tipler, it’s about the possibility that knowledge-creating organisms descended from humans will be able to put off the end of the universe indefinitely and become omniscient. Analogies between this state of affairs and the religious conceptions of gods and heaven are easy to find, and Tipler eagerly does so (he was religious and promoted the theory of intelligent design), but Deutsch rightly points out that you don’t have to become mystical about it to find the idea plausible, and carefully extracts the good from the bad where others were happy to just dismiss the entire thing out of hand. It’s an interesting thought experiment examining the real power of knowledge on a cosmological scale.

Finally, to complete your reading about the multiverse, chapter 9 pp. 200-207 and all of chapter 11 are essential, and chapter 11 of The Beginning of Infinity, simply called “The Multiverse”, is very good as well. See my glosses on them above.

And if you’ve read all those and would like my perspective on the rest of Deutsch and on reading Popper himself, come back and click over to here.