Physics

All fiction that does not violate the laws of physics is fact. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

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. — David Deutsch, The Fabric of Reality: The Science of Parallel Universes — and Its Implications

But in any case, understanding is one of the higher functions of the human mind and brain, and a unique one. Many other physical systems, such as animals’ brains, computers and other machines, can assimilate facts and act upon them. But at present we know of nothing that is capable of understanding an explanation – or of wanting one in the first place – other than a human mind. — David Deutsch, The Fabric of Reality: The Science of Parallel Universes — and Its Implications

Arthur C. Clarke once remarked that 'any sufficiently advanced technology is indistinguishable from magic'. This is true, but slightly misleading. It is stated from the point of view of a pre-scientific thinker, which is the wrong way round. 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. Anything that seems incomprehensible is regarded by science merely as evidence that there is something we have not yet understood, be it a conjuring trick, advanced technology or a new law of physics. — David Deutsch, The Fabric of Reality: The Science of Parallel Universes — and Its Implications

If something is permitted by the laws of physics, then the only thing that can prevent it from being technologically possible is not knowing how. — David Deutsch, The Beginning of Infinity: Explanations that Transform The World

The fundamental theories of modern physics explain the world in jarringly counter-intuitive ways. For example, most non-physicists consider it self-evident that when you hold your arm out horizontally you can feel the force of gravity pulling it downwards. But you cannot. The existence of a force of gravity is, astonishingly, denied by Einstein’s general theory of relativity, one of the two deepest theories of physics. This says that the only force on your arm in that situation is that which you yourself are exerting, upwards, to keep it constantly accelerating away from the straightest possible path in a curved region of spacetime — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

The biologist Peter Medawar described science as ‘the art of the soluble’, but the same applies to all forms of knowledge. All kinds of creative thought involve judgements about what approaches might or might not work. Gaining or losing interest in particular problems or sub-problems is part of the creative process and itself constitutes problem-solving. So whether ‘problems are soluble’ does not depend on whether any given question can be answered, or answered by a particular thinker on a particular day. But if progress ever depended on violating a law of physics, then ‘problems are soluble’ would be false. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

We know that achieving arbitrary physical transformations that are not forbidden by the laws of physics (such as replanting a forest) can only be a matter of knowing how. We know that finding out how is a matter of seeking good explanations. — David Deutsch, The Beginning of Infinity: Explanations that Transform The World

Again we were too parochial, and were led to the false conclusion that knowledge-bearing entities can be physically identical to non-knowledge-bearing ones; and this in turn cast doubt on the fundamental status of knowledge. But now we have come almost full circle. We can see that the ancient idea that living matter has special physical properties was almost true: it is not living matter but knowledge-bearing matter that is physically special. Within one universe it looks irregular; across universes it has a regular structure, like a crystal in the multiverse. — David Deutsch, The Fabric of Reality: The Science of Parallel Universes — and Its Implications

It is inevitable that we face problems, but no particular problem is inevitable. We survive, and thrive, by solving each problem as it comes up. And, since the human ability to transform nature is limited only by the laws of physics, none of the endless stream of problems will ever constitute an impassable barrier. So a complementary and equally important truth about people and the physical world is that problems are soluble. By ‘soluble’ I mean that the right knowledge would solve them. It is not, of course, that we can possess knowledge just by wishing for it; but it is in principle accessible to — David Deutsch, The Beginning of Infinity: Explanations that Transform The World

The fact that everything that is not forbidden by laws of nature is achievable, given the right knowledge. ‘Problems are soluble.’ – The ‘perspiration’ phase can always be automated. – The knowledge-friendliness of the physical world. – People are universal constructors. – The beginning of the open-ended creation of explanations. – The environments that could create an open-ended stream of knowledge, if suitably primed – i.e. almost all environments. – The fact that new explanations create new problems. — David Deutsch, The Beginning of Infinity: Explanations that Transform The World

Just as no one in 1900 could have foreseen the consequences of innovations made during the twentieth century – including whole new fields such as nuclear physics, computer science and biotechnology – so our own future will be shaped by knowledge that we do not yet have. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

As the physicist Richard Feynman said, ‘Science is what we have learned about how to keep from fooling ourselves. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

That is to say, every putative physical transformation, to be performed in a given time with given resources or under any other conditions, is either – impossible because it is forbidden by the laws of nature; or – achievable, given the right knowledge. — David Deutsch, The Beginning of Infinity: Explanations that Transform The World

Some types of transmutation happen spontaneously on Earth, in the decay of radioactive elements. This was first demonstrated in 1901, by the physicists Frederick Soddy and Ernest Rutherford, — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

Given a sufficiently precise description of the initial state of any isolated physical system, it would in principle predict the future behaviour of the system. Where the exact behaviour of a system was intrinsically unpredictable, it would describe all possible behaviours and predict their probabilities. In practice, the initial states of interesting systems often cannot be ascertained very accurately, and in any case the calculation of the predictions would be too complicated to be carried out in all but the simplest cases. — David Deutsch, The Fabric of Reality: Towards a Theory of Everything

Quantum theory is, as I have said, one such theory. But the other three main strands of explanation through which we seek to understand the fabric of reality are all ‘high level’ from the point of view of quantum physics. 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). — David Deutsch, The Fabric of Reality: Towards a Theory of Everything

More generally, what they lacked was a certain combination of abstract knowledge and knowledge embodied in technological artefacts, namely sufficient wealth. Let me define that in a non-parochial way as the repertoire of physical transformations that they would be capable of causing. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

What had changed? What made science effective at understanding the physical world when all previous ways had failed? — David Deutsch, The Beginning of Infinity: Explanations That Transform the World