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310 Conversion

abductive hypothesis was verified when the planet neptune was observed in
1846. The story repeated itself later in the century when it was discovered that
neptune in turn exhibited perturbations which eventually led to the discovery
of Pluto* in 1930 by a young American astronomer, Clyde Tombaugh, working
at the Lowell observatory in Flagstaff, Arizona. Abduction has slowly moved
to center stage in the philosophy of science. 45
The ifaluk and neptune cases exhibit the same formal structure: A basic
principle (people are naturally good; planetary orbits are shaped by the law of
gravitation) encounters some contradictory fact (young men commit evil acts;
Neptune’s orbit exhibits perturbations); an auxiliary hypothesis is added to the
theory (people can be possessed by evil spirits; the orbit is distorted by an as
yet unobserved planet); the added hypothesis mediates the conflict and allows
the original belief to stand unchallenged. The similarity between dissonance
reduction and abductive reasoning has been overlooked because the relevant
research communities have approached this process from opposite directions.
in the context of dissonance reduction, the purpose of the theorist is usually
to explain seemingly irrational behaviors, while in the philosophy of science,
the purpose is typically to explain scientific progress. The differences between
these two attitudes are irrelevant for the description of belief revision, but
the fact that theorists who hold these opposite attitudes have converged on
the same type of process should increase our confidence in its psychological
reality.
Mediation is a genuine change mechanism, because the contradictory
information is incorporated into the person’s belief system and becomes
represented as a new belief. Unlike the nervous car buyer who continues to
believe that he made the right decision in spite of negative consumer reports,
the members of the ifaluk tribe did not deny that their young men engaged
in evil acts, nor did astronomers deny that the orbit of Uranus exhibited per-
turbations. in both cases, the anomalous information was accepted as true.
nevertheless, neither the principle that people are naturally good nor the law
of gravitation were affected by the new information. in both cases, the added
auxiliary belief protects the challenged core belief, so the change is limited to
the periphery of the belief system.
in short, dissonance-reducing mechanisms such as discrediting the source,
bolstering, differentiation and mediation (abduction) handle contradictory

*
in 2006, the international Astronomical Union (iUA) decided that Pluto does not satisfy
all the criteria for being a planet. Gravitation is not affected by the change in label, so the
explanation for the perturbations of neptune remains the same.