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340 Conversion

that to perceive a contradiction between two beliefs, we have to have adopted
some background theory that claims that the states of affairs described by the
two beliefs mutually exclude each other. It is because we believe that large,
material solids cannot change shape, or simultaneously inhabit two different
shapes, that we must choose between different shapes for the Earth. As a sec-
ond example, our intuitive sense of space and geometry does not allow any
compromise between the statements that the Earth is at the center of the plan-
etary system and that the Sun is at its center. In our intuitive theory of three-
dimensional space, both states of affairs cannot hold at the same time.
Pairs of representation are more or less incompatible as a function of what
the background theory claims. It is not contradictory to believe that certain
cancers can be caused either by genetic factors or by some bacterium or virus
(but perhaps not both in any one case, except as an unlikely coincidence),
because the relevant background theories of physiology allow multiple causes
for certain cancers. Similarly, we can look back and forth between two maps of
the same area, drawn to different scales, without feeling any conflict, because
the relevant background theory – our intuitive understanding of mapmaking –
tells us how the two maps relate to each other and explains why one and the
same geographic feature looks different in the two maps. When the relevant
background theory does not claim incompatibility, the alternative representa-
tions are, as we say, different ways of looking at the matter, and we can go back
and forth between the two without feeling any need to choose.
In short, for a person to experience a cognitive conflict of the relevant sort,
his mental state must include at least the following components. There is some
resident theory Th1 that the person whose theory it is has adopted as true. The
second ingredient is a contender theory Th2, also judged as true. For there to
be a conflict, the two theories must be incompatible, which implies acceptance
of some overarching background theory Th0. The background theory implies
that Th1 and Th2 cannot both be true, although the person has adopted both
Th1 and Th2 as true. So we have the following components in a conflict scenario
for person S at time t:

S (t): true (Th0)
true (Th0) implies incompatible (Th1, Th2)
true (Th1)
true (Th2)

If a person possesses all these knowledge structures, then he is in a state of
dissonance and there is a need for change to restore the coherence of his belief
base. Cognitive conflicts are not logical contradictions; in particular, they are