Sustained progress through alternating guesswork and criticism requires a tradition of criticism

From Why Science is the Source of All Progress by David Deutsch.

For thousands of generations, we were in the dark. Our ancestors gazed at the night sky wondering what stars are- which was exactly the right thing to wonder about- using eyes and brains anatomically indistinguishable from ours. In every other field too, they tried to observe the world and to understand it. Occasionally they recognised simple patterns in nature, but when they tried to discover the underlying features of reality they failed almost completely. At the time of the Enlightenment they mistakenly believed that we “derive” knowledge of these features from the “evidence of our senses”, or “read” it from the “Book of Nature” by making observations, the doctrine called empiricism.

But science needs more than empiricism. Consider an audience watching a conjuring trick. The problem is not to predict that the trick will appear: I can predict that whenever a conjurer shows me an empty hat, something will later emerge from it. The problem is how the trick works, and that requires an explanation–a description of the unseen reality that accounts for the appearance.

For a new explanation one in turn needs creativity. To interpret dots in the sky as white-hot, million-kilometre spheres, one must first have conjured up the idea. That happens through guesswork - but guesswork usually produces errors, which is why observation is indeed essential to science, though not in the way supposed by empiricism. Its main use is to choose between theories that have already been guessed by rearranging, combining, altering and adding to existing ideas.

Sustained progress through alternating guesswork and criticism requires a tradition of criticism. Before the Enlightenment, that was a very rare sort of tradition. Usually, the whole point of traditions was to maintain the status quo and to defer to authority.

In turn, the scientific tradition of criticism soon led to the rule that theories must make testable predictions. This alone cannot be the secret of the success of science, however, because testable predictions have always been common too. Every prophet who claims that the sun will go out next Tuesday has a testable theory. Science must consist of testable explanations.

Though they helped to spur the Enlightenment, testable explanations are also not in themselves sufficient, since they existed long before science.

[snip]

Solutions always reveal new problems. So one must also always seek a better hard-to-vary explanation. That, at its heart, is the scientific method. As Richard Feynman remarked: “Science is what we have learned about how to keep from fooling ourselves.” Because it is prior to experimental testing, the practice of requiring good explanations can drive objective progress even in non-scientific fields. This is exactly what happened in the Enlightenment. Although the pioneers of that era did not put it that way, it was, and remains, the spirit of the age. It is the source of all progress.