The Fabric of Reality David Deutch

particular niche’, in the sense that a tiger might be thought to be the optimal
machine for occupying the ecological niche that tigers occupy. The standard
counter-examples to that sort of ‘survival of the fittest’ are adaptations, such
as the peacock’s tail, that seem to make the organism much 
less fit to exploit
its niche. Such objections seem to undermine the ability of Darwin’s theory to
meet its original purpose, which was to explain how the apparent ‘design’
(i.e. adaptations) in living organisms could have come into being through the
operation of ‘blind’ laws of physics on inanimate matter, without the
intervention of a purposeful Designer.
Richard Dawkins’ innovation, as set out in his books 
The Selfish Gene and
The Blind Watchmaker, is yet again the claim that the prevailing theory is
true after all. He argues that none of the current objections to the unadorned
Darwinian model turn out, on careful inspection, to have any substance. In
other words, Dawkins claims that Darwin’s theory of evolution does provide a
full explanation of the origin of biological adaptations. Dawkins elaborated
Darwin’s theory in its modern form as the theory of replicators. The replicator
that is best at getting itself replicated in a given environment will eventually
displace all variants of itself because, by definition, they are worse at getting
themselves replicated. It is not the fittest 
species variant that survives
(Darwin had hot quite realized this) but the fittest 
gene variant. One
consequence of this is that sometimes a gene may displace variant genes
(such as genes for less cumbersome tails in peacocks) by means (such as
sexual selection) that do not especially promote the good of the species or
the individual. But all evolution promotes the ‘good’ (i.e. the replication) of
the best-replicating genes — hence the term ‘selfish gene’. Dawkins meets
each of the objections in detail and shows that Darwin’s theory, correctly
interpreted, has none of the alleged flaws and does indeed explain the origin
of adaptations.
It is specifically Dawkins’ version of Darwinism that has become the
prevailing theory of evolution in the pragmatic sense. Yet it is still by no
means the prevailing 
paradigm. Many biologists and philosophers are still
haunted by the feeling that there is some fundamental gap in the
explanation. For example, in the same sense that Kuhn’s theory of ‘scientific
revolutions’ challenges the Popperian picture of science, there is a
corresponding evolutionary theory which challenges Dawkins’ picture of
evolution. This is the theory of 
punctuated equilibrium, which says that
evolution happens in short bursts, with long periods of unselected change in
between. This theory may even be factually true. It does not actually
contradict the ‘selfish gene’ theory, any more than Popperian epistemology
is contradicted by the proposition that conceptual revolutions do not happen
every day, or that scientists often resist fundamental innovation. But just as
with Kuhn’s theory, the way in which punctuated equilibrium and other
variant evolutionary scenarios have been presented, as solving some
allegedly overlooked problem in the prevailing evolutionary theory, reveals
the extent to which the explanatory power of Dawkins’ theory has yet to be
assimilated.
There has been a very unfortunate consequence, for all four strands, of the
prevailing theory’s being generally rejected as an explanation, without
serious rival explanations being current. It is that the proponents of the
prevailing theories — Popper, Turing, Everett, Dawkins and their supporters

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— have found themselves constantly on the defensive against obsolete
theories. The debate between Popper and most of his critics was (as I said
in Chapters 3 and 7) effectively about the problem of induction. Turing spent
the last years of his life in effect defending the proposition that human brains
do not operate by supernatural means. Everett left scientific research after
making no headway, and for several years the theory of the multiverse was
championed almost single-handedly by Bryce DeWitt until progress in
quantum cosmology in the 1970s forced its pragmatic acceptance in that
field. But the opponents of the multiverse theory 
as an explanation have
seldom advanced rival explanations. (David Bohm’s theory, which I
mentioned in Chapter 4, is an exception.) Instead, as the cosmologist
Dennis Sciama once remarked, ‘When it comes to the interpretation of
quantum mechanics, the standard of argument suddenly drops to zero.’
Proponents of the multiverse theory typically face a wistful, defiant but
incoherent appeal to the Copenhagen interpretation — which, however,
hardly anyone still believes. And finally, Dawkins has somehow become the
public defender of scientific rationality against, of all things, 
creationism, and
more generally against a pre-scientific world-view that has been obsolete
since Galileo. The frustrating thing about all this is that, so long as the
proponents of our best theories of the fabric of reality have to expend their
intellectual energies in futile refutation and re-refutation of theories long
known to be false, the state of our deepest knowledge cannot improve.
Either Turing or Everett could easily have discovered the quantum theory of
computation. Popper could have been elaborating the theory of scientific
explanation. (In fairness I must acknowledge that he did understand and
elaborate some connections between his epistemology and the theory of
evolution.) Dawkins could, for instance, be advancing his own theory of the
evolution of replicating ideas (memes).
The unified theory of the fabric of reality that is the subject of this book is, at
the most straightforward level, merely the combination of the four prevailing
fundamental theories of their respective fields. In that sense it too is the
‘prevailing theory’ of those four fields taken as a whole. Even some of the
connections between the four strands are quite widely acknowledged. My
thesis, therefore, also takes the form ‘the prevailing theory is true after all!’
Not only do I advocate taking each of the fundamental theories seriously as
an explanation of its own subject-matter, I argue that taken together they
provide a new level of explanation of a unified fabric of reality.
I have also argued that none of the four strands can be properly understood
independently of the other three. This is possibly a clue to the reason why all
these prevailing theories have not been believed. All four individual
explanations share an unattractive property which has been variously
criticized as ‘idealized and unrealistic’, ‘narrow’ or ‘naïve’ — and also ‘cold’,
‘mechanistic’ and ‘lacking in humanity’. I believe that there is some truth in
the gut feeling behind these criticisms. For example, of those who deny the
possibility of artificial intelligence, and find themselves in effect denying that
the brain is a physical object, a few are really only trying to express a much
more reasonable criticism: that the Turing explanation of computation seems
to leave no room, even in principle, for any future explanation 
in physical
terms of mental attributes such as consciousness and free will. It is then not
good enough for artificial-intelligence enthusiasts to respond brusquely that

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the Turing principle guarantees that a computer can do everything a brain
can do. That is of course true, but it is an answer in terms of prediction, and
the problem is one of explanation. There is an 
explanatory gap.
I do not believe that this gap can be filled without bringing in the other three
strands. Now, as I have said, my guess is that the brain is a classical
computer and not a quantum computer, so I do not expect the explanation of
consciousness to be that it is any sort of quantum-computational
phenomenon. Nevertheless, I expect the unification of computation and
quantum physics, and probably the wider unification of all four strands, to be
essential to the fundamental 
philosophical advances from which an
understanding of consciousness will one day flow. Lest the reader find this
paradoxical, let me draw an analogy with a similar problem from an earlier
era, ‘What is life?’ This problem was solved by Darwin. The essence of the
solution was the idea that the intricate and apparently purposeful design that
is apparent in living organisms is not built into reality 
ab initio, but is an
emergent consequence of the operation of the laws of physics. The laws of
physics had not specifically mandated the shapes of elephants and
peacocks, any more than a Creator had. They make no reference to
outcomes, especially emergent ones; they merely determine the rules under
which atoms and the like interact. Now, this conception of a law of nature as
a set of laws of motion is relatively recent. It can, I think, be credited
specifically to Galileo, and to some extent to Newton. The previous concept
of a law of nature had been that of a rule stating 
what happens. An example
is Johannes Kepler’s laws of planetary motion, which described how the
planets move in elliptical orbits. This is to be contrasted with Newton’s laws,
which are laws of physics in the modern sense. They make no mention of
ellipses, though they reproduce (and correct) Kepler’s predictions under
appropriate conditions. No one could have explained what life is under
Kepler’s conception of a ‘law of physics’, for they would have been looking
for a law that mandates elephants in the same way as Kepler’s laws
mandate ellipses. But Darwin was able to wonder how laws of nature that did
not mention elephants could nevertheless produce them, just as Newton’s
laws produce ellipses. Although Darwin made no use of any specific law of
Newton’s, his discovery would have been inconceivable without the world-
view underlying those laws. That is the sense in which I expect the solution
of the ‘What is consciousness?’ problem to depend on quantum theory. It will
invoke no specific quantum-mechanical processes, but it will depend
crucially on the quantum-mechanical, and especially the multi-universe,
world-picture.
What is my evidence? I have already presented some of it in Chapter 8,
where I discussed the multiverse view of knowledge. Although we do not
know what consciousness is, it is clearly intimately related to the growth and
representation of knowledge within the brain. It seems unlikely, then, that we
shall be able to explain what consciousness is, as a physical process, before
we have explained knowledge in physical terms. Such an explanation has
been elusive in the classical theory of computation. But, as I explained, in
quantum theory there is a good basis for one: knowledge can be understood
as complexity that extends across large numbers of universes.
Another mental attribute that is somehow associated with consciousness is
free will. Free will is also notoriously difficult to understand in the classical

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world-picture. The difficulty of reconciling free will with physics is often
attributed to determinism, but it is not determinism that is at fault. It is (as I
have explained in Chapter 11) classical spacetime. In spacetime, 
something
happens to me at each particular moment in my future. Even if what will
happen is unpredictable, it is already there, on the appropriate cross-section
of spacetime. It makes no sense to speak of my ‘changing’ what is on that
cross-section. Spacetime does not change, therefore one cannot, within
spacetime physics, conceive of causes, effects, the openness of the future
or free will.
Thus, replacing deterministic laws of motion by indeterministic (random)
ones would do nothing to solve the problem of free will, so long as the laws
remained classical. Freedom has nothing to do with randomness. We value
our free will as the ability to express, in our actions, who we as individuals
are. Who would value being random? What we think of as our 
free actions
are not those that are random or undetermined but those that are largely
determined by who we are, and what we think, and what is at issue.
(Although they are largely determined, they may be highly unpredictable in
practice for reasons of complexity.)
Consider this typical statement referring to free will: ‘After careful thought I
chose to do X; I could have chosen otherwise; it was the right decision; I am
good at making such decisions.’ In any classical world-picture this statement
is pure gibberish. In the multiverse picture it has a straightforward physical
representation, shown in Table 13.1. (I am not proposing to 
define moral or
aesthetic values in terms of such representations; I am merely pointing out
that, thanks to the multiverse character of quantum reality, free will and
related concepts are now compatible with physics.)
Thus Turing’s conception of computation seems less disconnected from
human values, and is no obstacle to the understanding of human attributes
like free will, provided it is understood in a multiverse context. The same
example exonerates Everett’s theory itself. On the face of it, the price of
understanding interference phenomena is to create or exacerbate many
philosophical problems. But here, and in many other examples I have given
in this book, we see that the very opposite is the case. The fruitfulness of the
multiverse theory in contributing to the solution of long-standing
philosophical problems is so great that it would be worth adopting even if
there were no physical evidence for it at all. Indeed, the philosopher David
Lewis, in his book 
On the Plurality of Worlds, has postulated the existence of
a multiverse for philosophical reasons alone.

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TABLE 13.1 
Physical representations of some statements referring to free
will.
Turning again to the theory of evolution, I can similarly attribute 
some sense
to those who criticize Darwinian evolution on the grounds that it seems
‘unlikely’ that such complex adaptations could have evolved in the given
time. One of Dawkins’ critics wants us to be as surprised by the biosphere as
we would be if a heap of spare parts thrown together happened to fall into
the pattern of a Boeing 747. On the face of it, this critic is forcing an analogy
between, on the one hand, billions of years of planet-wide trial and error, and
on the other hand an instantaneous accident of ‘happening to fall together’.
That would be wilfully to miss the whole point of the evolutionary
explanation. Nevertheless, is Dawkins’ precisely opposite position
completely adequate as an explanation? Dawkins wants us 
not to be
surprised that complex adaptations have come into being spontaneously. In
other words, he is claiming that his ‘selfish gene’ theory is a full explanation
— not of course for specific adaptations, but of how it was possible for such
complex adaptations to come into being.
But it is not a full explanation. There is an explanatory gap, and this time we
already know much more about how the other strands could fill it. We have
seen that the very fact that physical variable can store information, that they
can interact with one another to transfer and replicate it, and that such
processes are stable, all depend on the details of quantum theory.
Furthermore, we have seen that the existence of highly adapted replicators
depends on the physical feasibility of virtual-reality generation and
universality, which in turn can be understood as consequences of a deep
principle, the Turing principle, that links physics and the theory of
computation and makes no explicit reference to replicators, evolution or
biology at all.
An analogous gap exists in Popperian epistemology. Its critics wonder why
the scientific method works, or what justifies our reliance on the best
scientific theories. This leads them to hanker after a principle of induction or
something of the sort (though, as crypto-inductivists, they usually realize that
such a principle would not explain or justify anything either). For Popperians
to reply that there is no such thing as justification, or that it is never rational
to rely on theories, is to provide no explanation. Popper even said that ‘no

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theory of knowledge should attempt to explain why we are successful in our
attempts to explain things’ (
Objective Knowledge p. 23). But, once we
understand that the growth of human knowledge is a physical process, we
see that it cannot be illegitimate to try to explain how and why it occurs.
Epistemology is a theory of (emergent) physics. It is a factual theory about
the circumstances under which a certain physical quantity (knowledge) will
or will not grow. The bare assertions of this theory are largely accepted. But
we cannot possibly find an explanation of why they are true solely within the
theory of knowledge 
per se. In that narrow sense, Popper was right. The
explanation must involve quantum physics, the Turing principle and, as
Popper himself stressed, the theory of evolution.
The proponents of the prevailing theory, in each of the four cases, are put
permanently on the defensive by their critics’ harping on these explanatory
gaps. This often forces them to retreat into the core of their own strand.
‘Here I stand, I can do no other’ is their ultimate response, as they rely on
the self-evident irrationality of abandoning the unrivalled fundamental theory
of their own particular field. This only makes them seem even more narrow
to the critics, and it tends to engender pessimism about the very prospect of
further fundamental explanation.
Despite all the excuses I have been making for the critics of the central
theories, the history of all four strands shows that something very unpleasant
happened to fundamental science and philosophy for most of the twentieth
century. The popularity of positivism and of an instrumentalist view of
science was connected with an apathy, loss of self-confidence and
pessimism about genuine explanations at a time when the prestige,
usefulness and, indeed, funding for fundamental research were all at an all-
time high. Of course there were many individual exceptions, including the
four heroes of this chapter. But the unprecedented manner in which their
theories were simultaneously adopted and ignored speaks for itself. I do not
claim to have a full explanation for this phenomenon, but whatever caused it,
we seem to be coming out of it now.
I have pointed out one possible contributory cause, namely that individually,
all four theories have explanatory gaps that can make them seem narrow,
inhuman and pessimistic. But I suggest that when they are taken together as
a unified explanation of the fabric of reality, this unfortunate property is
reversed. Far from denying free will, far from placing human values in a
context where they are trivial and insignificant, far from being pessimistic, it
is a fundamentally optimistic world-view that places human minds at the
centre of the physical universe, and explanation and understanding at the
centre of human purposes. I hope we shall not have to spend too long
looking backwards to defend this unified view against non-existent
competitors. There will be no lack of competitors when, having taken the
unified theory of the fabric of reality seriously, we begin to develop it further.
It is time to move on.
TERMINOLOGY
paradigm The set of ideas through which those who hold it observe and
explain everything in their experience. According to Thomas Kuhn, holding a

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paradigm blinds one to the merits of another paradigm and prevents one
from switching paradigms. One cannot comprehend two paradigms at the
same time.
Copenhagen interpretation of quantum mechanics An idea for making it
easier to evade the implications of quantum theory for the nature of reality.
At moments of observation, the outcome in one of the universes supposedly
becomes real, and all the other universes — even those that contributed to
that outcome — are deemed never to have existed. Under this view, one is
not permitted to ask about what happens in reality between conscious
observations.
SUMMARY
The intellectual histories of the fundamental theories of the four strands
contain remarkable parallels. All four have been simultaneously accepted
(for use in practice) 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.
Whatever next?

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