Highlights from The Fabric of Reality by David Deutsch
Highlights from this book
-
In continually drawing a distinction between understanding and 'mere' knowing, I do not want to understate the importance of recorded, non-explanatory information. This is of course essential to everything from the reproduction of a micro-organism (which has such information in its DNA molecules) to the most abstract human thinking. So what distinguishes understanding from mere {10} knowing?
-
about what must be so, rather than what merely happens to be so;
-
reductionist. That is to say, science allegedly explains things reductively - by analysing them into components.
-
The reason why higher-level subjects can be studied at all is that under special circumstances the stupendously complex behaviour of vast numbers of particles resolves itself into a measure of simplicity and comprehensibility. This is called emergence: high-level simplicity 'emerges' from low-level complexity.
-
more detailed
-
is only when the discovery is complete that a fairly sequential argument, in a pattern something like Figure 3.3, can be presented. It
-
Not only is there constant backtracking, but the many sub-problems all remain simultaneously active and are addressed opportunistically. It is only when the discovery is complete that a fairly sequential argument, in a pattern something like Figure 3.3, can be presented.
-
There is no simple way of discovering the true nature of planets, given (say) a critique of the celestial-sphere theory and some additional observations, just as there is no simple way of designing the DNA of a koala bear, given the properties of eucalyptus trees. Evolution, or trial and error - especially the focused, purposeful form of trial and error called scientific discovery - are the only ways. For this reason, Popper has called his theory that knowledge can grow only by conjecture and refutation, in the manner of Figure 3.3, an evolutionary epistemology.
-
As I have said, the Inquisition were realists. Yet their theory has this in common with solipsism: both of them draw an arbitrary boundary beyond which, they claim, human reason has no access - or at least, beyond which problem-solving is no path to understanding.
-
For we are right to seek solutions to problems rather than sources of ultimate justification.
-
Anyone can search for it, find it and improve upon it if they take the trouble. They do not need authorization, or initiation, or holy texts. They need only be looking in the right way - with fertile problems and promising theories in mind. This open accessibility, not only of evidence but of the whole mechanism of knowledge acquisition, is a key attribute of Galileo's conception of reality.
-
Thus reality contains not only evidence, but also the means (such as our minds, and our artefacts) of understanding it.
-
We realists take the view that reality is out there: objective, physical and independent of what we believe about it. But we never experience that reality directly. Every last scrap of our external experience is of virtual reality. And every last scrap of our knowledge - including our knowledge of the non-physical worlds of logic, mathematics and philosophy, and of imagination, fiction, art and fantasy - is encoded in the form of programs for the rendering of those worlds on our brain's own virtual-reality generator.
-
Not everything that can be copied is a replicator. A replicator causes its environment to copy it: that is, it contributes causally to its own copying.
-
let us consider explicitly what the role of the user of virtual reality is. First, it is to kick the rendered environment and to be kicked back in return - in other words, to interact with the environment in an autonomous way. In the biological case, that role is performed by the external habitat. Second, it is to provide the intention behind the rendering. That is to say, it makes little sense to speak of a particular situation as being a virtual-reality rendering if there is no concept of the rendering being accurate or inaccurate. I have said that the accuracy of a rendering is the closeness, as perceived by the user, of the rendered environment to the intended one.
-
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. It depends on politics and economics and the outcomes of wars. It depends on what {184} people do: what decisions they make, what problems they solve, what values they adopt, and on how they behave towards their children.
-
Life achieves its effects not by being larger, more massive or more energetic than other physical processes, but by being more knowledgeable. In terms of its gross effect on the outcomes of physical processes, knowledge is at least as significant as any other physical quantity.
-
Now consider some mathematical calculation that is intractable on all classical computers, but suppose that a quantum computer can easily perform it using interference between, say, 10500 universes. To make the point more clearly, let the calculation be such that the answer (unlike the result of a factorization) cannot be tractably verified once we have it. The process of programming a quantum computer to perform such a computation, running the program and obtaining a result, constitutes a proof that the mathematical calculation has that particular result. But now there is no way of keeping a record of everything that happened during the proof process, because most of it happened in other universes, and measuring the computational state would alter the interference properties and so invalidate the proof. So creating an old-fashioned proof object would be infeasible; moreover, there is not remotely enough material in the universe as we know it to make such an object, since there would be vastly more steps in the proof than there are atoms in the known universe. This example shows that because of the possibility of quantum computation, the two notions of proof are not equivalent.
-
‘He thought,’ as Feynman once put it, ‘that he understood paper.’ But he was mistaken. Real, quantum-mechanical paper is wildly different from the abstract stuff that the Turing machine uses. The Turing machine is entirely classical, and does not allow for the possibility that the paper might have different symbols written on it in different universes, and that those might interfere with one another. Of course, it is impractical to detect interference between different states of a paper tape. But the point is that Turing’s intuition, because it included false assumptions from classical physics, caused him to abstract away some of the computational properties of his hypothetical machine, the very properties he intended to keep. That is why
-
In the multiverse view, the time traveller who visits Shakespeare has not come from the future of that copy of Shakespeare. He can affect, or perhaps replace, the copy he visits. But he can never visit the copy who existed in the universe he started from. And it is that copy who wrote the plays. So the plays had a genuine author, and there are no paradoxical loops of the kind envisaged in the story. Knowledge and adaptation are, even in the presence of pathways to the past, brought into existence only incrementally, by acts of human creativity or biological evolution, and in no other way.
-
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.
-
for computation, the computer scientist Tomasso Toffoli has remarked that ‘We never perform a computation ourselves, we just hitch a ride on the great Computation that is going on already.’
-
If, for instance, we want to understand why the world seems comprehensible, the explanation might be that the world is comprehensible. Such an explanation can, and in fact does, fit in with other explanations in other fields. But the theory that the world is half-comprehensible explains nothing and could not possibly fit in with explanations in other fields unless they explained it. It simply restates the problem and introduces an unexplained constant, one-half.
-
So far I have really only considered what might be called predictive emergence. For example, we believe that the predictions of the theory of evolution follow logically from the laws of physics, even though proving the connection might be computationally intractable. But the explanations in the theory of evolution are not believed to follow from physics at all. However, a non-hierarchical explanatory structure allows for the possibility of explanatory emergence.
-
The ends of the universe are, as Popper said, for us to choose.
-
is that intelligence is not only there to control physical events on the largest scale, it is also there to choose what will happen.
-
whether or not there is an omega point, wherever there is knowledge in the multiverse (complexity across many universes) there must also be the physical traces of the moral and aesthetic reasoning that determined what sort of problems the knowledge-creating entity chose to solve there.