Popper acknowledges that the philosophers of the modern period have emphasized the extraordinarily great explanatory power of science, and that they have debated how the discipline could make so much sense of the physical world. Popper agrees that there is clearly something different about science, since it is often accurate in predicting natural occurrences, which differentiates science from pseudo-science. Popper examines the theories of both the Continental school and English empiricism before asserting his own view: That science succeeds by depending upon refutation and criticism in the quest for determining truth.

The Continental school was led by René Descartes, who popularized rationalism. Rationalism is the belief that the world is logical by nature, which is why it can be understood using human reasoning. The Continental school thus asserts that people can arrive at truths through pure reasoning: Thus, science, by virtue of making use of rationality, can understand nature better than other, less-rational disciplines.

By contrast, the English empirical school argues that only experience can lead to the acquisition of knowledge. In other words, just thinking about something is not enough—people must go out, live in the world, and observe it in order to understand it.