David Deutsch Quotations

I myself believe that there will one day be time travel because when we find that something isn't forbidden by the over-arching laws of physics we usually eventually find a technological way of doing it.

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.

It is possible to build a virtual-reality generator whose repertoire includes every possible environment.

Our best theories are not only truer than common sense, they make more sense than common sense.

The overwhelming majority of theories are rejected because they contain bad explanations, not because they fail experimental tests.

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.

Time travel may be achieved one day, or it may not. But if it is, it should not require any fundamental change in world-view, at least for those who broadly share the world view I am presenting in this book.

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.

I chop and change between what is called 'work' and what is called 'recreation.' There are no discontinuities in my day. I only play tennis with people I find interesting.

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.

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.

To me quantum computation is a new and deeper and better way to understand the laws of physics, and hence understanding physical reality as a whole.

If we can't program it, we can't understand it.

Despite the unrivaled empirical success of quantum theory, the very suggestion that it may be literally true as a description of nature is still greeted with cynicism, incomprehension, and even anger.

The theory that the biosphere was created without evolution, a few thousand years ago, is ruled out by overwhelming scientific evidence. To claim that there are 'alternative (always better) Biblical explanations of the same data', which make creationism a reasonable alternative to our best theories of biology and physics, is appalling intellectual dishonesty.

Is the human race a universal constructor?

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.

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

If you can’t program it, you haven’t understood it.

Discovering a new explanation is inherently an act of creativity.

No precautions, and no precautionary principle, can avoid problems that we do not yet foresee. We need a stance of problem-fixing, not just problem-avoidance.

If you reject the infinite, you are stuck with the finite, and the finite is parochial... the best explanation of anything eventually involves universality, and therefore infinity. The reach of explanations cannot be limited by fiat.

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.

Like every other destruction of optimism, whether in a whole civilisation or in a single individual, these must have been unspeakable catastrophes for those who had dared to expect progress. But we should feel more than sympathy for those people. We should take it personally. For if any of those earlier experiments in optimism had succeeded, our species would be exploring the stars by now, and you and I would be immortal.

The whole [scientific] process resembles biological evolution. A problem is like an ecological niche, and a theory is like a gene or a species which is being tested for viability in that niche.

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.

The quantum theory of parallel universes is not the problem, it is the solution. It is not some troublesome, optional interpretation emerging from arcane theoretical considerations. It is the explanation, the only one that is tenable, of a remarkable and counter-intuitive reality.

Feeling insignificant because the universe is large has exactly the same logic as feeling inadequate for not being a cow.

Necessary truth is merely the subject-matter of mathematics, not the reward we get for doing mathematics. The object of mathematics is not, and cannot be, mathematical certainty. It is not even mathematical truth, certain or otherwise. It is, and must be, mathematical explanation.

Surely it is more interesting to argue about what the truth is, than about what some particular thinker, however great, did or did not think.

Every potential angle is being looked at the same way as the previous crimes, ... We do have investigative leads.

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.

As I understand it, the claim is that the less you use Homeopathy, the better it works. Sounds plausible to me.

The next chapter is likely to provoke many mathematicians. This can't be helped. Mathematics is not what they think it is.