Recently I read Norwood R. Hanson's short article called "Observations," in which he depicts a familiar scenario:
Imagine [Johannes Kepler] on a hill watching the dawn. With him is Tycho Brahe. Kepler regarded the sun as fixed: it was the earth that moved. But Tycho followed Ptolemy and Aristotle in this much at least: the eath was fixed and all other celestial bodies moved around it. Do Kepler and Tycho see the same thing in the east at dawn?He describes a situation in which two people view the same object but consider it to be different. In this case, obviously, Kepler saw the Earth moving while Tycho saw the Sun moving. So one might ask, why do we even need to incorporate all such mindsets, as Feyerabend proposes?
Surprisingly, this example rather highlights the need to compare and contrast between various different theories. When Kepler, Copernicus, Galileo, and other astronomers began to note observations that contradicted the geocentric model, they brought revolutionary changes in the field of astronomy. Yet had such inconsistent data challenged the geocentric model directly, the arrival of the heliocentric model might not have arrived at that point in time. Had such observations not been used, the world would have lived in scientific ignorance for a longer time.
Furthermore, the "established" theory could simply be one of the interpretations of the observations. Because different people view different objects differently, it is definitely possible that the interpretation is subjective and incomplete. This is exacerbated by the fact that most scientists try to prove current or established theories, rather than simply exploring possible scenarios. Such a fixed and short-sighted mindset is the source of such subjectivity, and it will be impossible to break away from that cycle unless alternative observations and theories are considered. Thus a combined analysis is the only way to determine the best theory that can result with given facts.
Thus fittingly, Hanson concludes by saying that,
Sorting out differences about data, evidence, observation, may require more than simply gesturing at observable objects. It may requires a comprehensive reappraisal of one's subject matter. This may be difficult, but it should not obscure the fact that nothing less than this may do."