Quotes from David Deutsch

The Principle of Optimism All evils are caused by insufficient knowledge.

My pencil and I are more clever than I.

Whenever a wide range of variant theories can account equally well for the phenomenon they are trying to explain, there is no reason to prefer one of them over the others, so advocating a particular one in preference to the others is irrational.

If two programs respond in the same way to every possible action by the user, then they render the same environment; if they would respond perceptibly differently to even one possible action, they render different environments.

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

Very little in nature is detectable by unaided human senses.

This is what we can achieve when, as Feynman said, we keep learning more about how not to fool ourselves.

Its quest for good explanations corrects the errors, allows for the biases and misleading perspectives, and fills in the gaps.

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!

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.

We know that achieving arbitrary physical transformations that are not forbidden by the laws of physics (such as replanting a forest) can only be a matter of knowing how. We know that finding out how is a matter of seeking good explanations.

Thus, although the existence of progress in the biosphere is what the theory of evolution is there to explain, not all evolution constitutes progress, and no (genetic) evolution optimizes progress.

knowledge has the unique ability to take aim at a distant target and utterly transform it while having scarcely any effect on the space between.

The very existence of Athens, however peaceful, is a deadly threat to Sparta's stasis. And therefore, in the long run, the condition for the continued stasis of Sparta (which means its continued existence, as they see it) is the destruction of progress in Athens (which from our perspective would constitute the destruction of Athens).

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

Existimos en múltiples versiones en universos denominados «momentos».

El tiempo no transcurre. Otros tiempos son, simplemente, casos especiales de otros universos.

For each natural number N, will the guest in room number N please move immediately to room number N (N +1)/2.' Then they announce, 'For all natural numbers N and M, will the Nth passenger from the Mth train please go to room number [(N + M)2 + N – M/2.

Lo que consideramos nuestras acciones «libres» no son las aleatorias o indeterminadas, sino las que están ampliamente «determinadas» por quienes somos, cómo pensamos y qué está en juego. (Si bien están ampliamente determinadas, pueden ser muy impredecibles por razones de complejidad.)

No somos únicamente «escoria química» pues que, por ejemplo, el comportamiento general de nuestro planeta, nuestra estrella y nuestra galaxia depende de una magnitud física emergente, pero fundamental: el conocimiento que hay en dicha escoria.

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.

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

discovering good explanations is hard, but the harder they are to find, the harder they are to vary once found.

Unless a society is expecting its own future choices to be better than its present ones, it will strive to make its present policies and institutions as immutable as possible.