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February 28 - August 9, 2025
in ancient times it was still possible for a very learned person to know everything that was known.
By ‘known’, I meant understood.
the general theory of relativity explains gravity in terms of a new, four-dimensional geometry of curved space and time.
Prediction – even perfect, universal prediction – is simply no substitute for explanation.
An extreme form of instrumentalism, called positivism (or logical positivism), holds that all statements other than those describing or predicting observations are not only superfluous but meaningless.
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.
We understand the fabric of reality only by understanding theories that explain it.
even though our stock of known theories is indeed snowballing, just as our stock of recorded facts is, that still does not necessarily make the whole structure harder to understand than it used to be. For while our specific theories are becoming more numerous and more detailed, they are continually being ‘demoted’ as the understanding they contain is taken over by deep, general theories. And those theories are becoming fewer, deeper and more general.
We are not heading away from a state in which one person could understand everything that is understood, but towards it.
That can happen only if the fabric of reality is itself highly unified, so that more and more of it can become understood as our knowledge grows.
I believe that such a unification and shift are now under way. The associated world-view is the theme of this book.
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.
High-level phenomena about which there are comprehensible facts that are not simply deducible from lower-level theories are called emergent phenomena.
The purpose of high-level sciences is to enable us to understand emergent phenomena, of which the most important are, as we shall see, life, thought and computation.
Quantum theory is one of what I shall call the four main strands of which our current understanding of the fabric of reality is composed.
the idea that theories of the initial state contain our deepest knowledge is a serious misconception.
It could even be that, between them, the laws governing biological and other emergent phenomena would entirely determine the laws of fundamental physics.
The fabric of reality does not consist only of reductionist ingredients like space, time and subatomic particles, but also of life, thought, computation
What makes a theory more fundamental, and less derivative, is not its closeness to the supposed predictive base of physics, but its closeness to our deepest explanatory theories.
They are the theory of evolution (primarily the evolution of living organisms), epistemology (the theory of knowledge) and the theory of computation (about computers and what they can and cannot, in principle, compute).
No econ?
The four of them taken together form a coherent explanatory structure that is so far-reaching, and has come to encompass so much of our understanding of the world, that in my view it may already properly be called the first real Theory of Everything.
it is not only physics that is being unified and explained here, and not only science, but also potentially the far reaches of philosophy, logic and mathematics, ethics, politics and aesthetics;
The basic experiments are remarkably austere.
they involve nothing but casting shadows.
What happens when a beam of light gets fainter is not that the photons themselves get fainter, but that they get farther apart, with empty space between them
There are no measurable continuous quantities in physics.
How does any object get from one place to another if there is not a continuous range of intermediate places for it to be on the way?
These places were bright when there were two slits in the barrier, but went dark when we cut a second pair of slits for the light to pass through. Opening those slits has interfered with the light that was previously arriving at X.
something must be coming through that second pair of slits to prevent the light from the first pair from reaching X.
there must be at least a trillion shadow photons accompanying each tangible one.
each universe affects the others only weakly, through interference phenomena.
Thus we have reached the conclusion of the chain of reasoning that begins with strangely shaped shadows and ends with parallel universes.
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.
Yet the existence of the multiverse is still a minority view among physicists. Why?
understanding the multiverse is a precondition for understanding reality as best we can.
every subatomic particle has counterparts in other universes, and is interfered with only by those counterparts.
the detection of interference between any two universes requires an interaction to take place between all the particles whose positions and other attributes are not identical in the two universes.
interference is strong enough to be detected only between universes that are very alike.
we do not need deep theories to tell us that parallel universes exist – single-particle interference phenomena tell us that.
non sequitur that a generalized prediction is tantamount to a new theory.
The disappointment experienced by Russell’s chicken has also been experienced by trillions of other chickens. This inductively justifies the conclusion that induction cannot justify any conclusions!
scientific discovery need not begin with observational evidence. But it does always begin with a problem.
theories that are capable of giving more detailed explanations are automatically preferred.
Inductivism is observation- and prediction-based, whereas in reality science is problem- and explanation-based.
It was specifically that idea, and not the heliocentric theory as such, that the authorities considered dangerous.
experience cannot prove that one is in a given environment,
all our external experiences are of virtual reality, generated by our own brains.
it is possible to build a virtual-reality generator whose repertoire includes every physically possible environment.
This is what makes reality comprehensible.
In the Popperian picture of scientific progress, it is not observations but problems, controversies, theories and criticism that are primary.
