Quotes from David Deutsch

Richard Feynman said, 'Science is what we have learned about how to keep from fooling ourselves.

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.

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.

The fabric of reality does not consist only of reductionist ingredients like space, time and subatomic particles, but also of life, thought, computation and the other things to which those explanations refer.

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).

This is why the Royal Society (one of the earliest scientific academies, founded in London in 1660) took as its motto 'Nullius in verba', which means something like 'Take no one's word for it.

One consequence of this tradition of criticism was the emergence of a methodological rule that a scientific theory must be testable (though this was not made explicit at first). That is to say, the theory must make predictions which, if the theory were false, could be contradicted by the outcome of some possible observation. Thus, although scientific theories are not derived from experience, they can be tested by experience – by observation or experiment

Testability is now generally accepted as the defining characteristic of the scientific method. Popper called it the 'criterion of demarcation' between science and non-science.

The criterion and the existing explanation are conflicting ideas. I shall call a situation in which we experience conflicting ideas a problem.

Changing our genes in order to improve our lives and to facilitate further improvements is no different in this regard from augmenting our skin with clothes or our eyes with telescopes.

In this book I argue that all progress, both theoretical and practical, has resulted from a single human activity: the quest for what I call good explanations.

They are 'universal constructors'.

Thus 'how do we know…?' is transformed into 'by what authority do we claim…?' The latter question is a chimera that may well have wasted more philosophers' time and effort than any other idea. It converts the quest for truth into a quest for certainty (a feeling) or for endorsement (a social status). This misconception is called justificationism.

For most of the history of our species, we had almost no success in creating such knowledge. Where does it come from? Empiricism said that we derive it from sensory experience. This is false. The real source of our theories is conjecture, and the real source of our knowledge is conjecture alternating with criticism.

while humans transform inhospitable environments like the biosphere into support systems for themselves. And, while every other organism is a factory for converting resources of a fixed type into more such organisms, human bodies (including their brains) are factories for transforming anything into anything that the laws of nature allow. They are 'universal constructors'.

Science is objective. And in my view we cannot take any experimental results seriously except in the light of good explanations of them.

Base metals can be transmuted into gold by stars, and by intelligent beings who understand the processes that power stars, but by nothing else in the universe.

I don't think it would be a good idea for scientists to have more political power. Scientists as a group are more inclined to try to derive an ought from an is, than the population at large.

The most important application of quantum computing in the future is likely to be a computer simulation of quantum systems, because that's an application where we know for sure that quantum systems in general cannot be efficiently simulated on a classical computer.

Humans may or may not have cosmic significance, and if they do, it will be by hitching a ride on the objective centrality of knowledge in the cosmic scheme of things.

The brain is the only kind of object capable of understanding that the cosmos is even there, or why there are infinitely many prime numbers, or that apples fall because of the curvature of space-time, or that obeying its own inborn instincts can be morally wrong, or that it itself exists.

Every problem that is interesting is also soluble.

Where we have good, testable explanations, they then have to be tested, and we drop the ones that fail the tests.

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.