Prediction

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, N/A

Beware the difference between prediction and prophecy. Prophecy purports to know things which cannot be known. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

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

The quest for good explanations is, I believe, the basic regulating principle not only of science, but of the Enlightenment generally. It is the feature that distinguishes those approaches to knowledge from all others, and it implies all those other conditions for scientific progress I have discussed: It trivially implies that prediction alone is insufficient. Somewhat less trivially, it leads to the rejection of authority, because if we adopt a theory on authority, that means that we would also have accepted a range of different theories on authority. And hence it also implies the need for a tradition of criticism. — David Deutsch, The Beginning of Infinity: Explanations that Transform The World

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. — David Deutsch, The Beginning of Infinity: Explanations that Transform The World

Both the future of civilization and the outcome of a game of Russian roulette are unpredictable, but in different senses and for entirely unrelated reasons. Russian roulette is merely random. Although we cannot predict the outcome, we do know what the possible outcomes are, and the probability of each, provided that the rules of the game are obeyed. The future of civilization is unknowable, because the knowledge that is going to affect it has yet to be created. Hence the possible outcomes are not yet known, let alone their probabilities. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

Observations are theory-laden. Given an experimental oddity, we have no way of predicting whether it will eventually be explained merely by correcting a minor parochial assumption or by revolutionizing entire sciences. We can know that only after we have seen it in the light of a new explanation. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

The second fundamental misconception in inductivism is that scientific theories predict that ‘the future will resemble the past’, and that ‘the unseen resembles the seen’ and so on. (Or that it ‘probably’ will.) But in reality the future is unlike the past, the unseen very different from the seen. Science often predicts – and brings about – phenomena spectacularly different from anything that has been experienced before. — David Deutsch, The Beginning of Infinity: Explanations That Transform the World

They can be understood only by being explained. Fortunately, our best theories embody deep explanations as well as accurate predictions. — David Deutsch, The Fabric of Reality: Towards a Theory of Everything

To say that prediction is the purpose of a scientific theory is to confuse means with ends. It is like saying that the purpose of a spaceship is to burn fuel. In fact, burning fuel is only one of many things a spaceship has to do to accomplish its real purpose, which is to transport its payload from one point in space to another. Passing experimental tests is only one of many things a theory has to do to achieve the real purpose of science, which is to explain the world. — David Deutsch, The Fabric of Reality: Towards a Theory of Everything

For example, you cannot predict what numbers will come up on a fair (i.e. unbiased) roulette wheel. But if you understand what it is in the wheel’s design and operation that makes it fair, then you can explain why predicting the numbers is impossible. — David Deutsch, The Fabric of Reality: Towards a Theory of Everything

Prediction – even perfect, universal prediction – is simply no substitute for explanation. — David Deutsch, The Fabric of Reality: Towards a Theory of Everything

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

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. — David Deutsch, The Beginning of Infinity: Explanations that Transform The World