David Deutsch is a 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)

• 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.

• 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)

• 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)

• Quantum computation is... a distinctively new way of harnessing nature... It will be the first technology that allows useful tasks to be performed in collaboration between parallel universes. (Ch. 9)

• 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 Law

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.

Weblog

• As I understand it, the claim is that the less you use Homeopathy, the better it works. Sounds plausible to me.http://www.qubit.org/people/david/index.php?blog=20040808030513

Attributed

• Is the human race a universal constructor?

• The theory of computation has traditionally been studied almost entirely in the abstract, as a topic in pure mathematics. This is to miss the point of it. Computers are physical objects, and computations are physical processes. What computers can or cannot compute is determined by the laws of physics alone, and not by pure mathematics.

• The size of the universe is no more depressing than the size of a cow.