David Deutsch

British physicist

David Deutsch (born 1953 in Haifa, Israel) is a British physicist at the University of Oxford. He is a non-stipendiary Visiting Professor in the Department of Atomic and Laser Physics at the Centre for Quantum Computation, Clarendon Laboratory. He pioneered the field of quantum computers, and is a proponent of the many-worlds interpretation of quantum mechanics.


The Fabric of Reality (1997)Edit

  • Surely it is more interesting to argue about what the truth is, than about what some particular thinker, however great, did or did not think.
  • Our best theories are not only truer than common sense, they make more sense than common sense...
  • The truly privileged theories are not the ones referring to any particular scale of size or complexity, nor the ones situated at any particular level of the predictive hierarchy—but the ones that contain the deepest explanations.
  • The overwhelming majority of theories are rejected because they contain bad explanations, not because they fail experimental tests.
  • A prediction, or any assertion, that cannot be defended might still be true, but an explanation that cannot be defended is not an explanation.
  • To say that prediction is the purpose of a scientific theory is to confuse means with ends. It is like saying that the purpose of a spaceship is to burn fuel. … Passing experimental tests is only one of many things a theory has to do to achieve the real purpose of science, which is to explain the world.
    • Ch. 1
  • The quantum theory of parallel universes is not the problem, it is the solution. It is not some troublesome, optional interpretation emerging from arcane theoretical considerations. It is the explanation—the only one that is tenable—of a remarkable and counter-intuitive reality.
    • Ch. 2
  • Reality contains not only evidence, but also the means (such as our minds, and our artefacts) of understanding it. There are mathematical symbols in physical reality. The fact that it is we who put them there does not make them any less physical.
    • Ch.3
  • Thus we can see that if we take solipsism seriously - if we assume that it is true and that all valid explanations must scrupulously conform to it - it self destructs. How exactly does solipsism, taken seriously, differ from its common-sense rival, realism? The difference is based on no more than a renaming scheme. Solipsism insists on referring to objectively different things (such as external reality and my unconscious mind, or introspection and scientific observation) by the same names. But then it has to introduce the distinction through explanations in terms of something like the 'outer part of myself'. But no such extra explanation would be necessary without its insistence on an inexplicable renaming scheme. Solipsism must also postulate the existence of an additional class of processes - invisible, inexplicable processes which give the mind the illusion of living in an external reality. The solipsist, who believes that nothing exists other than the contents of one mind, must also believe that that mind is a phenomenon of greater multiplicity than is normal supposed. It contains other-people-like thoughts, planet-like thoughts and laws-of-physics-like thoughts. These thoughts are real. They develop in a complex way (or pretend to), and they have enough autonomy to surprise, disappoint, enlighten or thwart other classes of thoughts which call themselves 'I'. Thus the solipsist's explanation of the world is in terms of interacting thoughts rather than interacting objects. But those thoughts are real, and interact according to the same rules that the realist says govern the interaction of objects. Thus solipsism, far from being a world view striped to its essentials, is actually just realism disguised and weighed down by additional baggage, introduced only to be explained away.
    • Ch.4
  • Think of all our knowledge-generating processes, our whole culture and civilization, and all the thought processes in the minds of every individual, and indeed the entire evolving biosphere as well, as being a gigantic computation. The whole thing is executing a self-motivated, self-generating computer program. More specifically it is, as I have mentioned, a virtual-reality program in the process of rendering, with ever-increasing accuracy, the whole of existence.
  • It is possible to build a virtual-reality generator whose repertoire includes every possible environment.
    • Ch. 6
  • Since building a universal virtual-reality generator is physically possible, it must actually be built in some universes.
    • Ch. 6
  • The next chapter is likely to provoke many mathematicians. This can't be helped. Mathematics is not what they think it is.
    • Ch. 10
  • Mathematical knowledge may, just like our scientific knowledge, be deep and broad, it may be subtle and wonderfully explanatory, it may be uncontroversially accepted; but it cannot be certain.
    • Ch. 10
  • Necessary truth is merely the subject-matter of mathematics, not the reward we get for doing mathematics. The object of mathematics is not, and cannot be, mathematical certainty. It is not even mathematical truth, certain or otherwise. It is, and must be, mathematical explanation.
  • Time travel may be achieved one day, or it may not. But if it is, it should not require any fundamental change in world-view, at least for those who broadly share the world view I am presenting in this book.
    • Ch. 12
  • Kuhn's theory suffers from a fatal flaw. It explains the succession from one paradigm to another in sociological or psychological terms, rather than as having primarily to do with the objective merit of the rival explanations. Yet unless one understands science as a quest for explanations, the fact that it does find successive explanations, each objectively better than the last, is inexplicable.
    • Ch. 13; commentary on the ideas of Thomas Kuhn, as presented in the book The Structure of Scientific Revolutions

Deutsch's LawEdit

This was Deutsch's response to the 2004 Edge Annual Question: "What is Your Law?"

Deutsch's Law: Every problem that is interesting is also soluble.

Corollary #1: Inherently insoluble problems are inherently boring.
Corollary #2: In the long run, the distinction between what is interesting and what is boring is not a matter of subjective taste but an objective fact.
Corollary #3: The problem of why every problem that is interesting is also soluble, is soluble.


  • As I understand it, the claim is that the less you use Homeopathy, the better it works. Sounds plausible to me.[1]

TED TalksEdit

  • The rational thing for a layperson to do is to take seriously the prevailing scientific theory.

External linksEdit

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