Top 70 David Deutsch Quotes (2025 Update)

1. “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.”

— David Deutsch

2. “If you can’t program it, you haven’t understood it.”

— David Deutsch

3. “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.”

— David Deutsch

4. “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.”

— David Deutsch

5. “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.”

— David Deutsch

6. “Discovering a new explanation is inherently an act of creativity.”

— David Deutsch

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

— David Deutsch

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

— David Deutsch

9. “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.”

— David Deutsch

10. “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.”

— David Deutsch

11. “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.”

— David Deutsch

12. “Every problem that is interesting is also soluble.”

— David Deutsch

13. “Is the human race a universal constructor?”

— David Deutsch

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

— David Deutsch

15. “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.”

— David Deutsch

16. “Copenhagen interpretation Niels Bohr’s combination of instrumentalism, anthropocentrism and studied ambiguity, used to avoid understanding quantum theory as being about reality.”

— David Deutsch

17. “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.”

— David Deutsch

18. “All fiction that does not violate the laws of physics is fact.”

— David Deutsch

19. “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.”

— David Deutsch

20. “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

21. “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.”

— David Deutsch

22. “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.”

— David Deutsch

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

— David Deutsch

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

— David Deutsch

25. “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.”

— David Deutsch

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

— David Deutsch

27. “Beware the difference between prediction and prophecy. Prophecy purports to know things which cannot be known.”

— David Deutsch

28. “Without error-correction all information processing, and hence all knowledge-creation, is necessarily bounded. Error-correction is the beginning of infinity.”

— David Deutsch

29. “The most important of all limitations on knowledge – creation is that we cannot prophecy: we cannot predict the content of ideas yet to be created, or their effects. This limitation is not only consistent with the unlimited growth of knowledge, it is entailed by it.”

— David Deutsch

30. “Optimism is, in the first instance, a way of explaining failure, not prophesying success. It says that there is no fundamental barrier, no law of nature or supernatural decree, preventing progress. Whenever.”

— David Deutsch

31. “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

32. “Some people become depressed at the scale of the universe, because it makes them feel insignificant. Other people are relieved to feel insignificant, which is even worse. But, in any case, those are mistakes. Feeling insignificant because the universe is large has exactly the same logic as feeling inadequate for not being a cow. Or a herd of cows. The universe is not there to overwhelm us; it is our home, and our resource. The bigger the better.”

— David Deutsch

33. “Because we are universal explainers, we are not simply obeying our genes. For.”

— David Deutsch

34. “SOCRATES: No, I am not sure of anything. I never have been. But the god explained to me why that must be so, starting with the fallibility of the human mind and the unreliability of sensory experience.”

— David Deutsch

35. “Sparta has no philosophers. That’s because the job of a philosopher is to understand things better, which is a form of change, so they don’t want it. Another difference: they don’t honour living poets, only dead ones. Why? Because dead poets don’t write anything new, but live ones do. A third difference: their education system is insanely harsh; ours is famously lax. Why? Because they don’t want their kids to dare to question anything, so that they won’t ever think of changing anything. How.”

— David Deutsch

36. “So we seek explanations that remain robust when we test them against those flickers and shadows, and against each other, and against criteria of logic and reasonableness and everything else we can think of. And when we can change them no more, we have understood some objective truth. And, as if that were not enough, what we understand we then control. It is like magic, only real. We are like gods!”

— David Deutsch

37. “We do not experience time flowing, or passing. What we experience are differences between our present perceptions and our present memories of past perceptions. We interpret those differences, correctly, as evidence that the universe changes with time. We also interpret them, incorrectly, as evidence that our consciousness, or the present, or something, moves through time.”

— David Deutsch

38. “There is only one way of thinking that is capable of making progress, or of surviving in the long run, and that is the way of seeking good explanations through creativity and criticism. What.”

— David Deutsch

39. “The ability to create and use explanatory knowledge gives people a power to transform nature which is ultimately not limited by parochial factors, as all other adaptations are, but only by universal laws. This is the cosmic significance of explanatory knowledge – and hence of people, whom I shall henceforward define as entities that can create explanatory knowledge.”

— David Deutsch

40. “Science is what we have learned about how to keep from fooling ourselves.’ By.”

— David Deutsch

41. “Using our explanations, we ‘see’ right through the behaviour to the meaning. Parrots copy distinctive sounds; apes copy purposeful movements of a certain limited class. But humans do not especially copy any behaviour. They use conjecture, criticism and experiment to create good explanations of the meaning of things – other people’s behaviour, their own, and that of the world in general. That.”

— David Deutsch

42. “An optimistic civilization is open and not afraid to innovate, and is based on traditions of criticism.”

— David Deutsch

43. “This inductively justifies the conclusion that induction cannot justify any conclusions.”

— David Deutsch

44. “It is a mistake to conceive of choice and decision-making as a process of selecting from existing options according to a fixed formula. That omits the most important element of decision-making, namely the creation of new options. Good.”

— David Deutsch

45. “Trying to rely on the sheer good luck of avoiding bad outcomes indefinitely would simply guarantee that we would eventually fail without the means of recovering.”

— David Deutsch

46. “Good political institutions are those that make it as easy as possible to detect whether a ruler or policy is a mistake, and to remove rulers or policies without violence when they are.”

— David Deutsch

47. “SOCRATES: You have? Oh – you said that you honour Athenians for our openness to persuasion. And for our defiance of bullies. But.”

— David Deutsch

48. “It follows that humans, people and knowledge are not only objectively significant: they are by far the most significant phenomena in nature – the only ones whose behaviour cannot be understood without understanding everything of fundamental importance.”

— David Deutsch

49. “The theory reaches out, as it were, from its finite origins inside one brain that has been affected only by scraps of patchy evidence from a small part of one hemisphere of one planet – to infinity. This reach of explanations is another meaning of ‘the beginning of infinity’. It is the ability of some of them to solve problems beyond those that they were created to solve.”

— David Deutsch

50. “Because pessimism needs to counter that argument in order to be at all persuasive, a recurring theme in pessimistic theories throughout history has been that an exceptionally dangerous moment is imminent.”

— David Deutsch