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When admiring centuries-old structures, people often forget that we see only the surviving ones. The overwhelming majority of structures built in medieval and earlier times have collapsed long ago, often soon after they were built.
What I am discussing is the possibility of understanding everything that is understood. That depends more on the structure of our knowledge than on its content. But
This is called emergence: high-level simplicity ‘emerges’ from low-level complexity. High-level phenomena about which there are comprehensible facts that are not simply deducible from lower-level theories are called emergent phenomena.
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.
This property of appearing only in lumps of discrete sizes is called quantization.
There are no measurable continuous quantities in physics.
To put that another way, shadow photons and tangible photons are affected in identical ways when they reach a given barrier, but the barrier itself is not identically affected by the two types of photon.
They are ‘parallel’ in the sense that within each universe particles interact with each other just as they do in the tangible universe, but each universe affects the others only weakly, through interference phenomena.
The heart of the argument is that single-particle interference phenomena unequivocally rule out the possibility that the tangible universe around us is all that exists.
understanding the multiverse is a precondition for understanding reality as best we can.
Therefore interference is observed only in special situations where the paths of a particle and its shadow counterparts separate and then reconverge
In practice this means that interference is strong enough to be detected only between universes that are very alike.
The first is that quantum theory is unrivalled in its ability to predict the outcomes of experiments, even if one blindly uses its equations without worrying much about what they mean.
The second is that
The quantum theory of parallel universes is not the problem, it is the solution.
It is hard to know where to begin in criticizing the inductivist conception of science – it is so profoundly false in so many different ways. Perhaps the worst flaw, from my point of view, is the sheer non sequitur that a generalized prediction is tantamount to a new theory.
If one does not accept a proposed explanation of a set of observations, making the observations over and over again is seldom the remedy. Still less can it help us to create a satisfactory explanation when we cannot think of one at all.
The fact that the same observational evidence can be ‘extrapolated’ to give two diametrically opposite predictions according to which explanation one adopts, and cannot justify either of them, is not some accidental limitation of the farmyard environment: it is true of all observational evidence under all circumstances.
Thus, contrary to the inductivist scheme shown in Figure 3.1, scientific discovery need not begin with observational evidence.
But it does always begin with a problem. By a ‘problem’ I do not necessarily mean a practical emergency, or a source of anxiety. I just mean a set of ideas that seems inadequate and worth trying to improve.
One solves a problem by finding new or amended theories, containing explanations which do not have the deficiencies, but do retain the merits, of existing explanations (Figure 3.2
In science the object of the exercise is not to find a theory that will, or is likely to, be deemed true for ever; it is to find the best theory available now,
Whereas an incorrect prediction automatically renders the underlying explanation unsatisfactory, a correct prediction says nothing at all about the underlying explanation.
a theory about observable events is untestable – that is, if no possible observation would rule it out – then it cannot by itself explain why those events happen in the way they are observed to and not in some other way.
this rule is really a special case of something that applies naturally to all problem-solving: theories that are capable of giving more detailed explanations are automatically preferred.
Popper has called his theory that knowledge can grow only by conjecture and refutation, in the manner of Figure 3.3, an evolutionary epistemology.
Inductivism is observation- and prediction-based, whereas in reality science is problem- and explanation-based.
He aptly called such tests cimenti, or ‘
(Legend has it, probably incorrectly, that as he rose to his feet he muttered the words ‘eppur si muove …’, meaning ‘and yet, it does move …
Galileo understood that if his method was indeed reliable, then wherever it was applicable its conclusions had to be preferable to those obtained by any other method.
Indeed, if making the right predictions were our only constraint, we could invent theories which say that anything we please is going on in space.
its fatal weakness, namely that it fails to solve the problem it purports to solve. It does not explain planetary motions ‘without having to introduce the complication of the heliocentric system
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.
A prediction, or any assertion, that cannot be defended might still be true, but an explanation that cannot be defended is not an explanation.
If, according to the simplest explanation, an entity is complex and autonomous, then that entity is real.
For we are right to seek solutions to problems rather than sources of ultimate justification.
The more fundamental a theory is, the more readily available is the evidence that bears upon it (to those who know how to look), not just on Earth but throughout the multiverse.
Thus physical reality is self-similar on several levels:
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.
Thus, the laws of physics may be said to mandate their own comprehensibility.
The fact is that to anyone who understands what virtual reality is, even genuine magic would be indistinguishable from technology, for there is no room for magic in a comprehensible reality.
A bad explanation (such as solipsism) may be true. Even the best and truest available theory may make a false prediction in particular cases, and those might be the very cases in which we rely on the theory.
theories are accepted when all their rivals are refuted, and not by virtue of numerous confirming instances.
entitled ‘Why Both Popper and Watkins Fail to Solve the Problem of Induction
but rather, taking for granted that it is invalid, how to justify any conclusion about the future from past evidence. And before you say that one doesn’t need to … DAVID: One doesn’t need to.
According to Popperian methodology, one should in these cases rely on the best-corroborated theory
‘one should’ rely on the best-corroborated theory, but why, exactly?
It is justified. But it was not justified by the evidence, if by ‘the evidence’ you mean all the experiments
Only argument ever justifies anything – tentatively, of course.
When Popper speaks of ‘rival theories’ to a given theory, he does not mean the set of all logically possible rivals: he means only the actual rivals,
