The Structure of Scientific Revolutions | Study Guide

Thomas Kuhn

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The Structure of Scientific Revolutions | Chapter 3 : The Nature of Normal Science | Summary



Paradigms establish what Kuhn calls "normal science." Because a paradigm does not initially address all possible questions and problems under its rubric—it is initially fairly limited both in its scope of application, and precision of practical articulation—there is much clarification and completion work to be done. This is what Kuhn refers to as "mop-up," and is what "engage[s] most scientists throughout their careers." "Mop-up" consists not in groundbreaking new discoveries, but rather in "an attempt to force nature into the preformed and relatively inflexible box that the paradigm supplies."

Activities during normal science do not aim at uncovering anomalies or new phenomena. When anomalies do occur, at least initially, they may go unnoticed or, if they are noticed, they are ignored or discarded. In the latter two cases, no new theory is developed in order to explain them, or if one is presented, the community typically rejects it. So, while the accretion of anomalies will eventually demand attention, the commitment to the existing paradigm makes progress possible by way of the aforementioned "mopping-up."

The level of detail and depth involved in the course of normal science reflects the focus on a specific area of nature. The scientific view is not panoramic. It does not attempt to synthesize results across disciplines, but rather the scientist seeks to sort out particular puzzles within their area of inquiry.

The detail and depth of the investigation are guided, according to Kuhn, by "three normal foci." The first is "that class of facts that the paradigm has shown to be particularly revealing of the nature of things." The second is that class of facts that "can be compared directly with predictions from the paradigm theory." And the third is "empirical work undertaken to articulate the paradigm theory."


The romantic view of the scientist toiling away until a new discovery is made that alters the course of humanity is dashed on the rocks of normal science. Kuhn's argument here is the process of doing science is far less dramatic than is depicted either in textbooks or in movies such as A Beautiful Mind. In fact, normal science in his view yields no new discovery but serves only to confirm or refute the paradigm's terms.

This is not to say Kuhn disparages the work done in normal science. Indeed, he points out the restrictions of the paradigm—the scope of inquiry set out and the rules directing it—"turn out to be essential to the development of science." This is because the paradigm "forces scientists to investigate ... nature in a detail and depth that would otherwise be unimaginable." Much like the narrow stylistic restrictions of a haiku poem force the poet to choose words more carefully and experiment with sentence structure more radically, the limits of a paradigm yield deep and innovative results. Moreover, achievements under the paradigm, Kuhn believes, are always at least partly permanent.

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