The Structure of Scientific Revolutions | Study Guide

Thomas Kuhn

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The Structure of Scientific Revolutions | Chapter 9 : The Nature and Necessity of Scientific Revolutions | Summary



The central questions in this chapter are: "What are scientific revolutions, and what is their function in scientific development?" A scientific revolution involves a developmental, yet noncumulative, episode of replacing an existing paradigm with a new one. This new paradigm is incompatible with the old one.

To the extent a scientific revolution results in a paradigm change, it is analogous to a political revolution. Political revolutions generally occur when a segment of the political community believe the existing institutions fail to solve problems they, in part, have created. Similarly, in "a narrow subdivision of the scientific community ... an existing paradigm has ceased to function adequately." The members of a political faction want the sort of change the institutions themselves resist or prohibit. The faction then works to propose a new institutional framework to replace the existing one. Meanwhile, other groups form to defend it. Further disagreements ensue until political discourse becomes impossible.

A similar process takes place in scientific communities. When a shared universe of discourse is no longer possible, the old paradigm is displaced. The new paradigm makes successful predictions its predecessor could not. Consequently, the two are logically incompatible, indeed "incommensurable with that which has gone before." Incommensurability is recognized not only because the two theories are in conflict, but also because of the anomalies' "stubborn refusal to be assimilated to existing paradigms."


In this chapter Kuhn brings together several conceptual threads that have been established in previous chapters. One is paradigm choice is not determined by normal science, since the latter occurs within the framework of the former, which as such, is presupposed. Moreover, paradigms are not accepted by the community according to external standards, but rather by their own standards of acceptability—those of the community of adherents. Therefore, not only is a paradigm self-sealing, but it is also fundamentally incommensurate with other paradigms. This is a striking blow to the persistent belief scientific development is progressive and cumulative.

Why shouldn't it be the case the new paradigm simply subsumes the old one as a special case? Kuhn's answer is "no theory can possibly conflict with one of its special cases." In other words an anomaly implies a discrepancy between it and the existing belief. If the anomaly cannot be solved using the existing paradigm, then the theory itself must be flawed. Paradigms inevitably involve the destruction and construction of beliefs about nature. In some sense this is not a radical view. A survey of scientific theories reveals profound developments are the result of one theory disproving the one currently in vogue. What is radical about Kuhn's position is how and why this displacement occurs.

Another important point in this chapter revolves around the norms of competing communities. Kuhn has already argued a given paradigm will leave problems unsolved. The problems are different from one paradigm to the next; therefore, debates among scientists involve questions about which problems are more significant. This, then, is a question of values, which lie outside of normal science. Scientific revolutions are, in an important sense, revolutions in values, a viewpoint scientists are not keen to embrace.

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