The Fabric of Reality: Towards a Theory of Everything (Penguin Science)

by David Deutsch

If we are to understand the world on more than a superficial level, it must be through those theories and through reason, and not through our preconceptions, received opinion or even common sense.

For example, a wall might be strong because its builders feared that their

enemies might try to force their way through it. This is a high-level explanation of the wall’s strength, not deducible from (though not incompatible with) the low-level explanation I gave above. ‘Builders’, ‘enemies’, ‘fear’ and ‘trying’ are all emergent phenomena. The purpose of high-level sciences is to enable us to understand emergent phenomena, of which the most important are, as

we shall see, life, thought and ...

Thus we explain a low-level physical observation – the presence of a copper atom at a particular location – through extremely high-level theories about emergent phenomena such as ideas, leadership, war and tradition.

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.

one hundred million kilometres from the torch, the frog would see on average only one flicker of light per day, but that flicker would be as bright as any that it observed at any other distance.

This flickering indicates that there is a limit to how thinly light can be evenly spread.

The quantuum nature of light. This is not paradoxical at all by itself.

What happens when a beam of light gets fainter is not that the photons themselves get fainter, but that they get farther apart, with empty space between them

Single-particle interference experiments such as I have been describing show us that the multiverse exists and that it contains many counterparts of each particle in the tangible universe.

On my second reading if this book i am calling BULLSHIT here. The experiments do not show this. It is one posse coherent explanation.

interference phenomena unequivocally rule out the possibility that the tangible universe around us is all that exists.

Not true in my opinion. Not established by DD either.

First, every subatomic particle has counterparts in other universes, and is interfered with only by those counterparts. It is not directly affected by any other particles in those universes.

This us also BULLSHIT! Each particle having its own wave function amounts to the same thing.

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.

There is plenty missing in this chain if reasoning.

it seemed to someone that the existing explanations could and should be improved upon.

if there are sources of ideas that behave as if they were independent of oneself, then they necessarily are independent of oneself. For if I define ‘myself’ as the conscious entity that has the thoughts and feelings I am aware of having, then the ‘dream-people’ I seem to interact with are by definition something other than that narrowly defined self,

Explanations are not justified by the means by which they were derived; they are justified by their superior ability, relative to rival explanations, to solve the problems they address.

We can see a Foucault pendulum swing in a plane that gradually seems to turn, revealing the rotation of the Earth beneath it.

So this is the killer experiment that proves the Vatican eas full of shit. Did Galileo know of this?

Working out what Bohm’s invisible wave will do requires the same computations as working out what trillions of shadow photons will do. Some

Bullshit. No it doesn't. It requires a standard first year computation.

For we are right to seek solutions to problems rather than sources of ultimate justification.

Every part of the Earth’s surface, on every clear night, for billions of years, has been deluged with evidence about the facts and laws of astronomy.

the self-similarity we call knowledge.

Real

The argument is that the complex behaviour of the supposedly nonexistent universe is so incredibly complex and unpredictable that it is abetter explanation to suppose that external reality exists.

Thus science and other forms of knowledge are made possible by a special self-similarity property of the physical world.

This is a weak and unconvincing segue.

What computers can or cannot compute is determined by the laws of physics alone, and not by pure mathematics. One

This is very reductionist though true. What is tge meaning of the computation?

The fact that this is possible is part of the self-similarity of physical reality that I mentioned in the previous chapter.

Not clear. It is only a conjecture. If it were true it would almist be logically inconsistent.

prehistoric cave paintings gave the viewer something of the experience of seeing animals that were not actually there.

Cool and pertinent

we naturally do not perceive our own nerves as being part of our environment.

A perfectly rendered roulette wheel must be just as usable for gambling as a real one.

science is about is understanding the whole of reality, of which only an infinitesimal proportion is ever experienced.

Imagination is a straightforward form of virtual reality.

What we experience directly is a virtual-reality rendering, conveniently generated for us by our unconscious minds from sensory data plus complex inborn and acquired theories (i.e. programs) about how to interpret them.

Awesome

All reasoning,

Sloppy. Reasoning is internal. Cogito.

is 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?

Isn't this the human brain? Or am i arguing for solipsism?

This means that a program which might at some point switch the user’s brain off, and never switch it on again, does not generate an environment for the user to experience and therefore does not qualify as a valid program for a virtual-reality generator. But

So by this definition nature is not a vr generator. Because it kills us off afer 75 years!

Like all theories, languages are invented and selected for their ability to solve certain problems.

logical reasoning is no less a physical process than scientific reasoning is, and it is inherently fallible.

Inanimate things never do anything as purposeful as that – or so the ancients thought. They had, of course, never seen a guided missile.

Nice example

the basis of life is molecular. It is the fact that there exist molecules which cause certain environments to make copies of those molecules. Such molecules are called replicators. More generally, a replicator is any entity that causes certain environments to copy it.

it follows from what I have said that ‘alive’ is at best a courtesy title when applied to the parts of an organism other than its DNA. An organism is not a replicator: it is part of the environment of replicators – usually the most important part after the other genes. The

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

regarding organisms as part of the environment of genes –

The point is that although all known life is based on replicators, what the phenomenon of life is really about is knowledge. We can give a definition of adaptation directly in terms of knowledge: an entity is adapted to its niche if it embodies knowledge that causes the niche to keep that knowledge in existence.

A really key insight

The point is that although all known life is based on replicators, what the phenomenon of life is really about is knowledge. We can give a definition of adaptation directly in terms of knowledge: an entity is adapted to its niche if it embodies knowledge that causes the niche to keep that knowledge in existence.

Key insight

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. The colour of the Sun ten billion years hence depends on gravity and radiation pressure, on convection and nucleosynthesis. It does not depend at all on the geology of Venus, the chemistry of Jupiter, or the pattern of craters on the Moon. But it does depend on what happens to intelligent life on the planet Earth.

we can perform a proof trapped inside a virtual-reality generator rendering the wrong physics.

But look at this proposition: David Deutsch cannot consistently judge this statement to be true. I am trying as hard as I can, but I cannot consistently judge it to be true. For if I did, I would be judging that I cannot judge it to be

true, and would be contradicting myself. But you can see that it is true, can’t you? This shows it is at least possible for a proposition to be unfathomable to one person yet self-evidently true to everyone else.

No flow of time is involved when we say when something happened, any more than a ‘flow of distance’ is involved if we say where it happened. But as soon as we say why something happened, we invoke the flow of time. If we say

our electric motors and dynamos in part to Faraday, and that the repercussions of his discovery are being felt to this day, we have in mind a picture of the repercussions beginning in 1831 and sweeping consecutively through all the moments of the rest of the nineteenth century, and then reaching the twentieth century and causing things like power stations to come into existence there. If we are not careful, we think of the twentieth century as initially ‘not yet affected’ by the momentous event of 1831, and then being ‘changed’ by the repercussions as they sweep past on their way to the twenty-first century and beyond. But usually we are careful, and we avoid that incoherent thought by never using the two parts of the common-sense theory of time simultaneously.

The laws of physics that determine one snapshot from another are the ‘glue’ that holds the snapshots together as a spacetime.