In the early Twentieth Century, most people viewed scientific hypotheses as theories that had not yet been proven. The philosopher of science Karl Raimund Popper flipped this view on its head, and argued that any theory-even one as well–established as Newtonian physics–was simply a hypothesis that had not yet been disproved.
Popper viewed science as a Darwinian struggle for survival between competing theories. Every theory is an imperfect representation of reality and vies for preeminence by surviving experimental scrutiny in the real world. Rigorous testing weeds out weaker theories, leaving only the strong to survive. Eventually, further experiments expose the flaws of the survivors, and yet stronger theories replace them as well. Science, for Popper, was a permanent battle for survival.
The engine that drives scientific progress, in Popper’s view, was an unending cycle that iterated between spotting an anomaly, formulating a working hypothesis, and submitting that theory to empirical and logical scrutiny to identify defects, steps elaborated below.
- Notice an anomaly. The cycle begins when a scientist bypasses a theory’s strong points to search out its weak spots. Prior to formulating the special theory of relativity, for example, Albert Einstein studied both existing theories of mechanics and electrodynamics with an eye to understanding their limitations. These shortcomings typically manifest themselves as anomalies, unusual findings that fall outside existing categories or defy explanation by established theories. An anomaly points in the direction of a mismatch between a simplified theory and complex reality, and flags a productive spot for further exploration.
- Formulate a bold conjecture. In the next step, the scientist formulates a working hypothesis to explain the anomaly. This stage demands the intellectual courage to break cleanly with conventional wisdom, and the imagination to envision a creative alternative. Popper idolized Einstein for his audacity, while working as a patent clerk, to fundamentally rethink our view of the universe. While Popper separated problem identification and hypothesis formulation into two distinct steps, he recognized that in practice they often co-evolved. The anomaly stimulates a hypothesis, which may necessitate a fresh look at the problem from a slightly different angle, and a revision to the hypothesis.
- Submit your conjecture to error elimination. Popper termed the third step in his cycle “error elimination,” in which the researcher submits her hypothesis to severe testing to expose its flaws. Error elimination includes scrupulous analysis of a theory to unearth logical inconsistencies. Karl Popper wrote a withering critique of Marxist thought, for example, based largely on internal inconsistencies within the theory. Error elimination also entails experiments to check predictions in the real world, such as the elegant test, designed and conducted by English astrophysicist Arthur Stanley Eddington, that found gravity bent light, just as Einstein’s theory predicted. The best way to eliminate errors, Popper argued, was to avoid tests designed to corroborate a theory, and design experiments with an eye to disproving one’s pet theory. A discredited theory is not a failure, but a triumph that eliminates error and clears the way for superior theories in the future.
Popper placed particular emphasis on error elimination, because he saw an asymmetry between what scientists can prove and what they can disprove. Spotting the millionth white swan, to use one of his best known metaphors, does not conclusively the theory that all swans are white. A single black swan disproves it conclusively. “Human reason is unlimited with regard to criticism,” Popper argued, “yet limited with regard to its powers of prediction.”
Popper viewed all theories as no more than working hypotheses, adopted not because they are true, but because they approximate truth closely enough to guide further inquiry. Theories provide imperfect representations of a complex and fluid world. Popper compared them to nets woven to catch portions of the reality as it swims by, while letting everything else pass through the mesh. Even the best theory will be flawed because it reduces complexity to simplicity, omits critical variables, and remains stable as the world turns. The experimental loop provided the engine to continuously improve imperfect theories.