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such a situation is to estimate whether it would be worthwhile to take the perceived
risk considering the possible reward one may expect. Research in optimal foraging
and evolutionary biology is a good source of inspiration.
1.1.3
Conceptual Revolutions
Thomas Kuhn's theory is sociologically and historically motivated. In contrast, Paul
Thagard's computational approach to conceptual revolutions focuses on the logic
(Thagard
1992
). Conceptual revolutions replace a whole system of concepts and
rules with a new system. Thagard points out that there has been little detailed
explanation of such changes, although historians and philosophers of science
have noted the importance of scientific revolutions. Thagard focused on questions
concerning how exactly a conceptual revolution takes place.
Thagard argued that the ultimate acceptance of a scientific theory essentially de-
pends on the
explanation coherence
of the theory. If a theory with fewer assumptions
can explain more phenomenon than an alternative theory, then the simpler one is
considered to be superior. Thagard demonstrated the idea with examples such as
the conceptual development of plate tectonics in the latest geological revolution and
Darwin's natural selection theory. A conceptual revolution may involve structural
and non-structural changes. Thagard illustrated a structural change with the example
of the continental drift to modern theories, and a non-structural change with the
example of how the meaning of the concept of evolution changed through Darwin's
origins of species.
Accounts of scientific change can be roughly categorized as accretion theories
and gestalt theories. In accretion theories, a new conceptual system is developed by
adding new nodes and links. Kuhn criticized accretion theories of scientific growth.
Kuhn's Gestalt switch is radically different. If the accretion theories are akin to
a biological evolution through a chain of single mutation instances, then Kuhn's
Gestalt switch is like an evolution with multiple simultaneous mutations. Different
approaches have different implications. For example, accretion theories would have
difficulties to explain why it would be worthwhile for scientists to take apparent
setbacks. In the metaphor of searching in a problem space, are we following a
greedy search strategy or are we ready to tolerate short-term loss to maximize
our longer term goal? Accretion theories are more suitable to describe the initial
growth stages than later stages of decline. Gestalt theories are more suitable for
explaining the dynamics of a system of multiple paradigms. In both cases, more
detailed mechanisms are necessary to account for how a new system is constructed
and how it replaces an old system.
Thagard comes up with such mechanisms by asking the question: what makes a
system standout? He suggests that we should focus on rules, or mechanisms, that
govern how concepts are connected. For example, we should consider the dynamics
of how concepts are connected in terms of the variation of strengths of links over
time. Adding a link between two concepts can be seen as strengthening an existing
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