Quotes from David Deutsch

Could it be that the moral imperative not to destroy the means of correcting mistakes is the only moral imperative?

everything that is not forbidden by laws of nature is achievable, given the right knowledge.

Whenever we try to improve things and fail, it is not because the spiteful (or unfathomably benevolent) gods are thwarting us or punishing us for trying, or because we have reached a limit on the capacity of reason to make improvements, or because it is best that we fail, but always because we did not know enough, in time.

there can be only one type of person: universal explainers and constructors.

there is only one way of making progress: conjecture and criticism

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

The last room number is not infinity. First of all, there is no last room.

Consider also the revolutionary utopians, who typically achieve only destruction and stagnation. Though they are blind optimists, what defines them as utopians is their pessimism that their supposed utopia, or their violent proposals for achieving and entrenching it, could ever be improved upon. Additionally,

If it turns out that all this time we have merely been studying the programming of a cosmic planetarium, then that would merely mean that we have been studying a smaller portion of reality than we thought. So what? Such things have happened many times in the history of science, as our horizons have expanded beyond the Earth to include the solar system, our Galaxy, other galaxies, clusters of galaxies and so on, and, of course, parallel universes.

Not only is there constant backtracking, but the many subproblems all remain simultaneously active and are addressed opportunistically.

Shoddy explanations that yield correct predictions are two a penny, as UFO enthusiasts, conspiracy-theorists and pseudo-scientists of every variety should (but never do) bear in mind.

inventing falsehoods is easy, and therefore they are easy to vary once found; discovering good explanations is hard, but the harder they are to find, the harder they are to vary once found.

One of the consequences of optimism is that one expects to learn from failure – one's own and others'.

There is an explanatory link between ought and is, and this provides one of the ways in which reason can indeed address moral issues.

It would be astonishing if the details of a primitive, static society's collapse had any relevance to hidden dangers that may be facing our open, dynamic and scientific society, let alone what we should do about them.

Since theories can contradict each other, but there are no contradictions in reality, every problem signals that our knowledge must be flawed or inadequate.

It is a classic example of the deceptiveness of the senses: the Earth looks and feels as though it is at rest beneath our feet, even though it is really rotating. As for the celestial sphere, despite being visible in broad daylight (as the sky), it does not exist at all.

Therefore, if the ancient Greeks had known that a warm growing season occurs in Australia at the very moment when, as they believed, Demeter is at her saddest, they could have inferred that there was something wrong with their explanation of seasons.

As the ancient philosopher Heraclitus remarked, 'No man ever steps in the same river twice, for it is not the same river and he is not the same man.

Behind it all is surely an idea so simple, so beautiful, that when we grasp it – in a decade, a century, or a millennium – we will all say to each other, how could it have been otherwise?

it is only when a theory is a good explanation – hard to vary – that it even matters whether it is testable. Bad explanations are equally useless whether they are testable or not.

What if you'd rather not know? You may not like these predictions. Your friends and colleagues may ridicule them. You may try to modify the explanation so that it will not make them, without spoiling its agreement with observations and with other ideas for which you have no good alternatives. You will fail. That is what a good explanation will do for you: it makes it harder for you to fool yourself.

Good/bad explanation An explanation that is hard/easy to vary while still accounting for what it purports to account for.

But one thing that all conceptions of the Enlightenment agree on is that it was a rebellion, and specifically a rebellion against authority in regard to knowledge.