The Fabric of Reality

The Fabric of Reality by David Deutsch is his attempt at explaining the world a bit better. For this, he uses quantum theory to better understand what we experience. See below my notes/highlights throughout the book:


The whole goal of the book is to expand/explain some “deep theories about the structure of reality.” This in contrast to common sense, preconceptions, received opinion, authority. The answers may be very counterintuitive.

1. The Theory of Everything

There is a chance we might understand many more things than our ancestors. This doesn’t mean we can remember more facts or words (Greek poets were much better than us at this), but that our theories might explain (and let us understand) more about (the fabric of) reality.

This is done through having the right concepts, explanations, and theories.

“Scientific theories explain the objects and phenomena of our experience in terms of an underlying reality which we do not experience directly.”

  • Others say it’s about prediction, this view is called instrumentalism
  • But, prediction is no substitute for explanation
  • We need theories (from bold conjectures) and then test them (experimentation)
  • We can do this by testing them in the physical world (our ‘oracle’)

“To say that prediction is the purpose of a scientific theory is to confuse means with ends.” (passing the experimental test is only one of the aspects of a good theory)

“The deeper an explanation is, the more remote from immediate experience are the entities to which it must refer.” (we don’t see atoms, or stars far away, or evolution directly)

“… understanding comes through explanatory theories…” The generality of a these theories may make it possible for us to understand more.

“But at present we know of nothing that is capable of understanding an explanation – or of wanting one in the first place – other than a human mind.”

We can even understand (new) situations without knowing this beforehand. That is the reach of explanations. If you know maths, then you can also understand Roman numerals (but you will have to learn some facts about them first).

We understand the fabric of reality only by understanding theories that explain it.”

There is both specialisation and a broadening going on (in scientific explanation). The reach of our explanations goes further than before, we understand areas we had no clue about before.

Deutsch’s thesis is that the depth of theories is winning (versus breath). We are moving towards a state in which a person can understand everything. In the book Deutsch argues for / lays the groundwork of a Theory of Everything.

Emergence is the high-level simplicity that emerges from low-level complexity (e.g. social systems from people, people from atoms). Some areas that can be studied are life, thought, and computation.

Holism is a mistaken way of thinking about emergence. This belief states that “the only legitimate explanations are in terms of higher-level systems.”… “There are explanations at every level of the hierarchy.”

Some components of the Theory of Everything are theories about electromagnetism, nuclear forces, and gravity. Two theories in physics stand out: 1) general theory of relativity (space, time, gravity), and 2) quantum theory. A quantum theory of gravity is something that could be very important/have great reach.

The four strands of Deutsch’s Theory of Everything are:

  1. Quantum theory
  2. Theory of evolution
  3. Epistemology (theory of knowledge)
  4. Theory of computation (what, in principle, computer can compute)

Scientific knowledge, like all human knowledge, consists primarily of explanations. Mere facts can be looked up, and predictions are important only for conducting crucial experimental tests to discriminate between competing scientific theories that have already passed the test of being good explanations. As new theories supersede old ones, our knowledge is becoming both broader (as new subjects are created) and deeper (as our fundamental theories explain more, and become more general). Depth is winning. Thus we are not heading away from a state in which one person could understand everything that was understood, but towards it. Our deepest theories are becoming so integrated with one another that they can be understood only jointly, as a single theory of a unified fabric of reality. This Theory of Everything has a far wider scope than the ‘theory of everything’ that elementary particle physicists are seeking, because the fabric of reality does not consist only of reductionist ingredients such as space, time and subatomic particles, but also, for example, of life, thought and computation.”

2. Shadows

Using a torch (light beam), Deutsch shows how it demonstrates the multiverse.

He first talks about light being fuzzy (not having BRIGHT and DARK next to each other, but shades in between at the edges). If light moves very far away you can say it arrives in parts (yes/no), this is called quantization.

“There are no measurable continuous quantities in physics.”

So how is there a fuzzy area (penumbra)? That is because light does bend. And this is caused by interference (multiverse), so even one photon (light) is bent.

This inference is not a special case of light/photons, it occurs for every sort of particle. For every ‘tangible’ particle, there are infinite? (or at last a trillion) ‘shadow’ particles.

Collectively we may call the shadow particles a ‘parallel universe’. And all of those together, the ‘multiverse’.

In other words, particles are grouped into parallel universes. They are ‘parallel’ in the sense that within each universe particles interact with each other just as they do in the tangible universe, but each universe affects the others only weakly, through interference phenomena.

But why are these effects so small? “… every subatomic particle has counterparts in other universes, and is interfered only by those counterparts.” and “… the detection of interference between any two universes requires an interaction to take place between all the particles whose positions and other attributes are not identical in the two universes.”

The quantum theory of parallel universes is not the problem, it’s the solution.”

In interference experiments there can be places in a shadow-pattern that go dark when new openings are made in the barrier casting the shadow. This remains true even when the experiment is performed with individual particles. A chain of reasoning based on this fact rules out the possibility that the universe we see around us constitutes the whole of reality. In fact the whole of physical reality, the multiverse, contains vast numbers of parallel universes.”

3. Problem-solving

Deutsch talks about the ‘problem of induction’. Science was thought to move forward by observation, both in discovering of scientific theories and justification of them. It went like this, 1) observations, 2) are generalized to form a theory, 3) then more observations, 4) justify the theory. This is wrong.

He also argues that Solipsism (that only one mind can exist and the whole external world is an illusion outside of that mind) can’t be disproven.

A generalized prediction doesn’t equal a new theory. Bertrand Russell exemplified this with a chicken who was fed everyday, until the day it was slaughtered.

“… repeated observations cannot justify theories, but in doing so it entirely misses (or rather, accepts) a more basic misconception: namely, that the inductive extrapolation of observations to form new theories is even possible. In fact it’s impossible to extrapolate observations unless one has already placed them within an explanatory framework.”

Inductivism matches with our common-sense intuition that we can learn from experience.

Science progresses through an explanation-centered theory of knowledge. This is based on Karl Popper (Conjectures and Refutations). We start with our current/best theories (which are inadequate) and test these with observations (the ‘experience’). If these don’t confer, we make better/newer theories that can explain more/deeper parts of reality.

The process of scientific discovery or the problem-solving process is as follows, 1) problem, 2) conjectured solutions, 3) criticism (including experimental tests), 4) replacement of erroneous theories, 5) new problem.

“… theories that are capable of giving more detailed explanations are automatically preferred.”

“So all theories are being subjected to variation and selection, according to criteria which are themselves subject to variation and selection. The whole process resembles biological evolution.”

“One difference is that in biology variations (mutations) are random, blind and purposeless…” There is also no biological equivalent of an argument (although survival of something could maybe fill that role partly).

In fundamental areas of science, observations of even smaller, more subtle effects are driving us to ever more momentous conclusions about the nature of reality. Yet these conclusions cannot be deduced by pure logic from the observations. So what makes them compelling? That is the ‘problem of induction’. According to inductivism, scientific theories are discovered by extrapolating the results of observations, and justified when corroborating observations are obtained. In fact, inductive reasoning is invalid, and it is impossible to extrapolate observations unless one already has an explanatory framework for them. But the refutation of inductivism, and also the real solution of the problem of induction, depends on recognizing that science is a process not of deriving predictions from observations, but of finding explanations. We seek explanations when we encounter a problem with existing ones. We then embark on a problem-solving process. New explanatory theories begin as unjustified conjectures, which are criticized and compared according to the criteria inherent in the problem. Those that fail to survive this criticism are abandoned. The survivors become the new prevailing theories, some of which are themselves problematic and so lead us to seek even better explanations. The whole process resembles biological evolution.”

4. Criteria for Reality

This chapter deals with the question of how we can draw conclusions about objective, external reality from (our mind’s) subjective experience and reason.

Therefore [Galileo] insisted that scientific reasoning took precedence not only over intuition and common sense, but also over religious doctrine and revelation.”

Deutsch critiques Behaviourism and other forms of solipsisms (because they lack explanatory power.

A prediction, or any assertion (bold conjecture), that cannot be defended might still be true, but an explanation that cannot be defended (tested/falsified) is not an explanation.”

A good metaphor for looking at reality is to see if something ‘kicks back’. This could be a rock that you kick, and it could be the light that reflects of faraway planets and ‘kicks’ your retina. This metaphor/thinking tool, originally by Dr. Johnson, is used throughout the book.

If, according to the simplest explanation, an entity is complex and autonomous, then that entity is real.” or put into words related to complexity theory, “If a substantial amount of computation would be required to give us the illusion that a certain entity is real, then that entity is real.”

Observational evidence is indeed evidence, not in the sense that any theory can be deduced, induced or in any other way inferred from it, but in the sense that it can constitute a genuine reason for preferring one theory to another.”

[W]hat is genuinely out there is evidence, or, more precisely, a reality that will respond with evidence if we interact appropriately with it.”

Thus reality contains not only evidence, but also the means (such as our minds, and our artefacts) of understanding it.”

The self-similarity of reality that we put/observe in theories, images, symbols can be called knowledge.

Although solipsism and related doctrines are logically self-consistent, they can be comprehensively refuted simply by taking them seriously as explanations. Although they all claim to be simplified world-views, such an analysis shows them to be indefensible over-elaborations of realism. Real entities behave in a complex and autonomous way, which can be taken as the criterion for reality: if something ‘kicks back’, it exists. Scientific reasoning, which uses observation not as a basis for extrapolation but to distinguish between otherwise equally good explanations, can give us genuine knowledge about reality.”

5. Virtual Reality

“What computers can or cannot compute is determined by the laws of physics alone, and not by pure mathematics. One of the most important concepts of the theory of computation is universality. A universal computer is usually defined as an abstract machine that can mimic the computations of any other abstract machine in a certain well-defined class.”

Virtual reality is where this universality (or restrictions of some computations) can best be shown. In the book ‘virtual reality’ is used as a theoretical concept, but one day our computers might (within the laws of physics) do as described.

“We shall see that the existence of virtual reality does not indicate that the human capacity to understand the world is inherently limited, but, on the contrary, that it is inherently unlimited.” (that is quite the claim)

In the virtual reality experience you can see things that are not possible in real-life (e.g. flying through a mountain), but not logically impossible things (factorizing a prime number). It also doesn’t show/simulate internal experiences (e.g. your feelings, but they can of course be influenced by what you see/hear – the external experiences). (see table p105)

“Eventually it will become possible to bypass the sense organs altogether and directly stimulate the nerves that lead from them to the brain.” This machine that could render any sensation would be called the universal image generator.

Deutsch also argues that all our external experiences are, in effect, virtual reality (rendering on our brain’s own virtual reality generator). “All reasoning, all thinking and all external experiences are forms of virtual reality.”

“Virtual reality is not just a technology in which computers simulate the behaviour of physical environments. The fact that virtual reality is possible is an important fact about the fabric of reality. It is the basis not only of computation, but of human imagination and external experience, science and mathematics, art and fiction.”

6. Universality and the Limits of Computation

[I]s there a single virtual-reality generator, buildable once and for all, that could be programmed to render any environment that the human mind is capable of experiencing?”

One trick to work towards this goal is to slow the processing of the human’s brain, vs speeding up the computer’s speed.

Deutsch defines a class of logically possible environments as Cantgotu environments.

He also re-defines the Turing principle as follows “It is possible to build a virtual-reality generator whose repertoire includes every physically possible environment” (see p133-135 for the steps)

“The diagonal argument shows that the overwhelming majority of logically possible environments cannot be rendered in virtual reality. I have called themCantgotu environments. There is nevertheless a comprehensive self-similarity in physical reality that is expressed in the Turing principle (see above). So a single, buildable physical object can mimic all the behaviours and responses of any other physically possible object or process. This is what makes reality comprehensible.”

7. A Conversation About Justification

This chapter tackles one objection, namely common sense.

“… inductivism rests upon a mistaken idea of science as seeking predictions on the basis of observations, rather than as seeking explanations in response to problems. … science does make progress, by conjecturing new explanations and then choosing between the best ones by experiment.”

This is justified (something Deutsch emphasizes) because it leaves fewer loose ends, it’s more generalizable, meshes better with other explanations, etc.

For a theory to win an argument, all its rivals must be untenable, and that includes all the variants of the rivals which anyone has thought of.

Language also plays an important role in our theories and does quite a lot of the work. I think that somewhere else Deutsch also mentions that this is one of the reasons why many philosophers like to put things in mathematical equations (in a way also a language) that is less confusing/more universal.

The process of argument (making theories and testing them) starts in the middle. There is no ‘end’ that we can reach, nor a ‘beginning’ from which to base it all on.

8. The Significance of Life

“… life is a fundamental phenomenon of nature.” (as first coined by Aristotle) ” … life is theoretically fundamental and has large physical effect.”

Life on earth is based on replicators (genes/DNA/ACGT), the genetic code is the language of them.

A gene can function as a replicator only in certain environments.”

A replicator causes its environment to copy itself: that is, it contributes causally to its own copying.”

Deutsch mentions junk DNA. The views on this has changed and much of the ‘junk’ is now considered important/functional.

An organism is not a replicator: it is part of the environment of replicators.”

So an organism is the immediate environment which copies the real replicators: the organism’s genes.”

Also see The Selfish Gene. And The Extended Phenotype (not read yet)

Genes embody knowledge about their niches.”

It’s the knowledge that is passed on. So a piece of knowledge, not the physical genes, is adapted to a specific niche.

On how we have influence and how life shapes the world/universe: “Thus one cannot predict the future of the Sun without taking a position on the future of life on Earth, and in particular on the future of knowledge.” or in other words “… the future history of the universe depends on the future history of knowledge.”

Even non-intelligent life has grossly transformed many times its own mass of the surface and atmosphere of the Earth.” (think about oxygen from plants making up a part of the atmosphere)

Deutsch makes some remarks about the multiverse (re-read later).

Where there is knowledge, there must have been life, at least in the past.”

Scientific progress since Galileo has seemed to refute the ancient idea that life is a fundamental phenomenon of nature. It has revealed the vast scale of the universe, compared with the Earth’s biosphere. Modern biology seems to have confirmed this refutation, by explaining living processes in terms of molecular replicators, genes, whose behaviour is governed by the same laws of physics as apply to inanimate matter. Nevertheless, life is associated with a fundamental principle of physics – the Turing principle – since it is the means by which virtual reality was first realized in nature. Also, despite appearances, life is a significant process on the largest scales of both time and space. The future behaviour of life will determine the future behaviour of stars and galaxies. And the largest-scale regular structure across universes exists where knowledge-bearing matter, such as brains or DNA gene segments, has evolved.

9. Quantum Computers

A quantum computer is a machine that uses uniquely quantum-mechanical effects, especially interferences, to perform wholly new types of computation that would be impossible, even in principle, on any Turing machine and hence on any classical computer.”

Universal virtual-reality generators are possible (as defined and explained earlier). Because of quantum computing, they are also tractable (i.e. possible to be made/calculated in a reasonable amount of time)

Chaos theory is about limitations on predictability in classical physics, stemming from the fact that almost all classical systems are inherently unstable.” It’s very sensitive to initial conditions. See a YouTube video by Veritasium about this. Deutsch does however state that our world is built on quantum theory, not classical mechanics. “In quantum mechanical, small deviations from a specified initial state tend to cause only small deviations from the predicted final state.” If I understand it correctly, the fanning out (from the original state) is the ‘real’ reason why there is unpredictability (e.g. in the weather). “Even if we knew the initial conditions perfectly, the multiplicity, and therefore the unpredictability of the motion, would remain.” (i.e. if we could know exactly where a pendulum with 3 arms/parts starts, we still wouldn’t perfectly predict the state of it 10 seconds later.

Deutsch makes a distinction between unpredictability and intractability. Unpredictability as per above (so different behaviours in different universes for quantum theory). “Intractability, by contrast, is a computational-resource issue.”

Quantum theory/experiments don’t only make probabilistic predictions, there can also be “non-random interference phenomena” with one outcome.

Deutsch proved in 1985 that a universal quantum computer was possible.

There is much more detailed talk about why he came to this conclusion and how it works. One challenge put forward is Shor’s algorithm (he asks you to explain it without acknowledging the multiverse).

Quantum computing makes a new level of cryptography possible, one that can detect eavesdroppers.

The laws of physics permit computers that can render every physically possible environment without using impractically large resources. So universal computation is not merely possible, as required by the Turing principle, it is also tractable. Quantum phenomena may involve vast numbers of parallel universes and therefore may not be capable of being efficiently simulated within one universe. However, this strong form of universality still holds because quantum computers can efficiently render every physically possible quantum environment, even when vast numbers of universes are interacting. Quantum computers can also efficiently solve certain mathematical problems, such as factorization, which are classically intractable, and can implement types of cryptography which are classically impossible. Quantum computation is a qualitatively new way of harnessing nature [or the fabric of reality].”

10. The Nature of Mathematics

This chapter is a bit far away from what I know or find interesting. Deutsch also remarks that it’s an attack/rebuttal of standard mathematical views, ones I do not share (or know about).

In mathematics, proof play the role of ‘kicking back’.

For the idea that mathematics yields certainties is a myth too.”

As mathematical reasoning became more sophisticated, it inevitably moved ever further away from everyday intuition.”

Deutsch argues that intuitionism (in mathematics, as conceived of by Brouwer – Dutch mathematician) is the solipsism of mathematics.

He also makes reference to Hilbert and then to Gödel (from Gödel’s incompleteness theorem). “Thanks to Gödel, we know that there will never be a fixed method of determining whether a mathematical proposition is true, any more than there is a fixed way of determining whether a scientific theory is true. Nor will there ever be a fixed way of generating new mathematical knowledge. Therefore progress in mathematics will always depend on the exercise of creativity. It will always be possible, and necessary, for mathematicians to invent new types of proof.”

(on the remaining pages I haven’t marked anything, so although it might be important – it didn’t register with me)

Abstract entities that are complex and autonomous exist objectively and are part of the fabric of reality. There exist logically necessary truths about these entities, and these comprise the subject-matter of mathematics. However, such truths cannot be known with certainty. Proofs do not confer certainty upon their conclusions. The validity of a particular form of proof depends on the truth of our theories of the behaviour of the objects with which we perform the proof. Therefore mathematical knowledge is inherently derivative, depending entirely on our knowledge of physics. The comprehensible mathematical truths are precisely the infinitesimal minority which can be rendered in virtual reality. But the incomprehensible mathematical entities (e.g. Cantgotu environments) exist too, because they appear inextricably in our explanations of the comprehensible ones.”

11. Time: The First Quantum Concept

We shall see that there is no such thing as the flow of time.” Wow, what a statement and one that seems very counter-intuitive.

To put it bluntly, the reason why the common-sense theory of time is inherently mysterious is that it is inherently nonsensical. It is not just that it is factually inaccurate. We shall see that, even in its own terms, it does not make sense.”

(after making various illustrations – all which don’t really help) “So there is no single ‘present moment’, except subjectively. From the point of view of an observer at a particular moment, that moment is indeed singled out, and may uniquely be called ‘now’ by that observer, just as any position in space is singled out as ‘here’ from the point of view of an observer at that position.”

This does also make me think of a wider concept of ‘now’, that 1 millisecond is the now of say 1 mile around you, of 1 second around you is a part of the world, of 1 minute is part of space, etc. The ‘now’ of Alpha Centauri is much different (as is the place) as here. More discussion about time in The Order of Time.

We do not experience time flowing, or passing. What we experience are differences between our present perceptions and our present memories of past perceptions. We interpret those differences, correctly, as evidence that the universe changes with time.” but, he continues, “We also interpret them, incorrectly, as evidence that our consciousness, or the present, or something, moves through time.”

No accurate picture of the framework of time can be a moving or changing picture. It must be static.”

Our idea of time consists of two concepts that don’t work well together. We explain things as flowing/moving through time (things have causes). But we also describe things (and have static picture of that thing).

None of Newton’s physical theories refers to the flow of time, nor has any subsequent physical theory referred to, or been compatible with, the flow of time.”

Space and time, considered together like this as a four-dimensional entity, are called spacetime.” … “Spacetime is sometimes referred to as the ‘block universe’.”

This would (maybe) mean that the future is not open, there is no free will, everything is set in stone (or spacetime). But Deutsch goes on further, and will argue that the future is ‘open’.

Subjectively, the future of a given observer may be said to be ‘open from that observer’s point of view’ because one cannot measure or observe one’s own future.” (but objectively it’s still fixed). The lottery will fall one way or the other, no matter if you don’t know this beforehand. “So according to spacetime physics, the openness of the future is an illusion … In reality we make no choices.”

The property of snapshots being determined by other snapshots is called determinism.”

So the snapshots have an intrinsic order, defined by their contents and by the real laws of physics. Any one of the snapshots, together with the real laws of physics, not only determines what all the others are, it determines their order, and it determines its own place in the sequence. In other words, each snapshot has a ‘time stamp’ encoded in its physical contents.”

The predictability of one event from another does not imply that those events are cause and effect.”

So, all of this was according to pre-quantum physics. And that is what is messing us up, “because spacetime physics is false.”

Physical reality is not a spacetime. It is a much bigger and more diverse entity, the multiverse.”

(earlier he also repeats how causation works: “For X to be a cause of Y, two conditions must hold: first, that X and Y both happen; and second, that Y would not have happened if X had been otherwise.”)

Multiverses then are infinite, but types of experiences/events are present in definitive proportions. Time would still be a sequence of events, but these events would happen in many universes. A moment here is referred to as a “super-snapshot”.

“[T]he super-snapshots beginning with a particular moment would be entirely and exactly determined by the previous super-snapshots. This complete determinism would not give rise to complete predictability, even in principle, because making a prediction would require a knowledge of what had happened in all the universes, and each copy of us can directly perceive only one universe.” But still, this picture also isn’t quite right, the ‘neat’ separation of universes next to each other (figure 11.6) isn’t correct.

In the multiverse, snapshots do not have ‘time stamps’.” So that snapshot, that can’t be an accurate description. There is no overarching framework in which to put the multiverse.

Therefore there is no fundamental demarcation between snapshots of other times and snapshots of other universes. This is the distinctive core of the quantum concept of time: Other times are just special cases of other universes.”

Only from our perspective do these other snapshots (our history/past) have special meaning. Our conditional logic (if … then) is based on this framework (us seeing a very similar snapshot in other times).

“… any snapshot that is present at all is present in an infinity of copies.” As stated above, it’s just about the proportion in which such a snapshot is present.

Quantum theory does not in general determine what will happen in a particular snapshot, as spacetime physics does. Instead, it determines what proportion of all snapshots in the multiverse will have a given property.”

In the end, he does ‘defend’ the standard notion of time, “Alle experimental results currently available to us are compatible with the approximation that time is a sequence of moments.” but, “… theory tells us that it must break down in certain types of physical process.”

Time (or even the concept of it) comes to a halt at the Big Bang and black holes.

“… on a sub-microscopic scale quantum effects again warp and tear the fabric of spacetime, and that closed loops of time – in effect, tiny time machines – exist on that scale”

… spacetime physics is never an exact description of reality.”

There is still cause-and-effect, and determinism.

Deutsch also remarks that heat and entropy (more randomness/variations) is one part of why we may see the flow of time going in one direction.

Time is not a sequence of moments, nor does it flow. Yet our intuitions about the properties of time are broadly true. Certain events are indeed causes and effects of one another. Relative to an observer, the future is indeed open and the past fixed, and possibilities do indeed become actualities.”

(the end-of-chapter summary is very short) “Time does not flow. Other times are just special cases of other universes.”

12. Time Travel

If we slow down the body (or freeze it), we can have future-directed time travel. Ditto for if we accelerate or decelerate, we experience less time (time dilation).

If we want to travel back in time in virtual reality, it can only be a real/faithfull picture/time before we interact with it.

… one can use a time machine only to travel to times and places at which it has existed. In particular, one cannot use it to travel back to a time before its construction was completed.”

See figure 12.3 (p306) for a rendering of the virtual time machine.

(about wanting to change the past) “Changing the past means choosing which past snapshot to be in, not changing any specific past snapshot into another one.”

Time travel is currently only possible (to the past) at the Planck time scale.

But if we (one day) would be able to go to the past, it would be that of another universe, so the info they would bring would not be about ‘our’ future (but could still be useful).

Possession of a time machine would allow us access to knowledge from an entirely new source, namely the creativity of minds in other universes.” (and with quantum computers we’re already doing this in a way)

Time travel may or may not be achieved one day, but it is not paradoxical. If one travels into the past one retains one’s normal freedom of action, but in general ends up in the past of a different universe. The study of time travel is an area of theoretical study in which all four of my main strands are significant, quantum mechanics, with its parallel universes and the quantum concept of time; the theory of computation, because of the connections between virtual reality and time travel, and because the distinctive features of time travel can be analysed as new modes of computation; and epistemology and the theory of evolution, because of the constraints they impose on how knowledge can come into existence.”

13. The Four Strands

Kuhn argues that scientific knowledge ‘revolutions’ happen only after they break through the old guard, their ways of thinking, their paradigm. But Deutsch (and Popper – The Myth of the Framework) think otherwise. Deutsch argues that the theory only explains how theories succeed each other, not how rival explanations compete. (Deutsch is also positive about the views of researchers when in that role (vs being ‘humans’))

The problem is outdated theories that Popper, Dawkins, and others have to defend their theories against.

Deutsch also argues that we do have free will, see page 339 (let’s call it quantum free will).

The intellectual histories of the fundamental theories of the four strands contain remarkable parallels. All four have been simultaneously accepted (for in practical use) and ignored (as explanations of reality). One reason for this is that, taken individually, each of the four theories has explanatory gaps, and seems cold and pessimistic. To base a world-view on any of them individually is, in a generalized sense, reductionist. But when they are taken together as a unified explanation of the fabric of reality, this is no longer so.”

14. The Ends of the Universe

Our knowledge is what makes us special and what makes sure that we have influence over the universe.

Deutsch explains that in the end of the universe (The Big Crunch) we might expect to make infinitely many computations.

… intelligence will survive, and knowledge will continue to be created, until the end of the universe.”

reality is comprehensible.”

He also speaks about the omega-point theory (related to the computations we can do at the Big Crunch). The computer there will be omnipotent, but only with the available matter and energy, and within the laws of physics.

Our knowledge is becoming broader (more areas) and deeper (we can understand more with less theories).

“… the four strands: the quantum physics of the multiverse, Popperian epistemology, the Darwin-Dawkins theory of evolution and a strengthened version of Turing’s theory of universal computation.”