The Structure of Scientific Revolutions (1962) by Thomas Kuhn stands as a seminal work that revolutionized the philosophy of science. As a scholar who shifted his focus from physics to the history of science, and later to the philosophy of science, Kuhn challenged prevailing notions about the nature of scientific progress, introducing concepts such as paradigms, normal science, and scientific revolutions. Situated at the nexus of science, history, and philosophy, Kuhn’s work upended the view of science as a linear and cumulative pursuit, instead characterizing it as a realm consisting of periods of incremental progress interrupted by upheavals in fundamental beliefs. The Structure of Scientific Revolutions was controversial upon publication and remains controversial in some circles today. His introduction of a humanist, subjective perspective to science bothered some who wished to keep science free of any seemingly irrational elements. The book is also notable for helping the word “paradigm” to achieve widespread use in the 20th century. Modern Library has named it one of the 100 best nonfiction books since 1900.

This guide references The Structure of Scientific Revolutions: 50th Anniversary Edition, published by The University of Chicago Press in 2012.

Content Warning: The book suggests a view of history and science that may be problematic to or not inclusive of certain views and religions.

Summary

At the heart of Thomas Kuhn’s book is the concept of a scientific paradigm. Kuhn begins by explaining that a paradigm represents the set of accepted beliefs, theories, and practices shared by a scientific community at a given time. It serves as the framework within which scientists operate, guiding their research endeavors and shaping their interpretations of empirical data. Paradigms provide a sense of normalcy and stability to scientific inquiry during periods of what Kuhn terms “normal science.”

Normal science, Kuhn goes on to explain, characterizes the routine and puzzle-solving activities of scientists within the confines of a specific paradigm. He argues that normal science is akin to puzzle solving because it is the type of work that proceeds according to accepted rules, with the expectation that an answer is assured. During this phase, scientists work within established frameworks, refining existing theories and conducting experiments that align with the accepted paradigm. The cumulative nature of normal science contributes to the gradual development of scientific knowledge within a given framework.

However, Kuhn proceeds to introduce a crucial element that disrupts the perceived continuity of scientific progress: anomalies. Anomalies are observations or phenomena that do not align with the expectations set by the existing paradigm. These anomalies accumulate over time and create a sense of crisis within the scientific community. Kuhn argues that crises are essential for the emergence of scientific revolutions. Crises, Kuhn contends, are characterized by uncertainty and wider experimentation than is typical under normal science. These conditions are conducive for the forming of new theories and new paradigms.

Scientific revolutions, in Kuhn’s framework, represent a radical departure from existing paradigms. They occur when the accumulation of anomalies reaches a critical point, challenging the explanatory power of the prevailing paradigm. In response to this crisis, a new paradigm emerges, fundamentally altering the scientific landscape. Kuhn contends that scientific revolutions are not mere extensions of existing knowledge but involve a paradigm shift, wherein the new paradigm renders the old one obsolete. Kuhn then acknowledges that paradigm shifts may be met with resistance from scientists, because they call into question prior work that was done under the old paradigm. For social and psychological reasons, scientists may be reluctant to detach from an old paradigm and adhere to a new one.

Scientific revolutions, Kuhn posits, represent a shift in worldview. Scientists who are affected by a paradigm change inevitably view the world differently after accepting the new paradigm. They pay attention to new problems and use terms and concepts differently. They inevitably shift how they approach the world and therefore their work. Kuhn goes on to argue that revolutions, while important, have been largely rendered invisible by textbooks, which are considered the authority on current scientific knowledge. Kuhn characterizes scientific education as a particularly rigid and consensus-building form of education, noting this education is enabled by textbooks. These textbooks often omit historical context, instead presenting current scientific paradigms as if they have always been accepted. This, he argues, erases the importance of scientific revolutions.

Kuhn’s characterization of scientific revolutions challenges the traditional positivist view of science as a cumulative, linear progression. The notion of paradigm shifts introduces a more dynamic and complex model of scientific development, acknowledging the discontinuities and disruptions inherent in the evolution of scientific thought. One key aspect of Kuhn’s work is the recognition of incommensurability between paradigms. Incommensurability refers to the idea that paradigms are not directly comparable because they involve different sets of assumptions, methods, and ways of perceiving the world. This challenges the positivist notion that scientific progress involves a seamless transition between well-defined theories. Kuhn argues that after a paradigm shift, scientists operate within a new framework that may be fundamentally different from the previous one, making direct comparisons difficult.

Kuhn closes the book by questioning the very nature of scientific progress. He points out that many people believe science to be a continual pursuit of objective truth. He argues, however, that rather than getting ever-closer to a single, objective truth, science instead moves away from less precise, less complete ways of viewing the world. In the postscript to the book, Kuhn then responds to many of the critiques that arose after the initial publication of the book. One of his main points is that his original work revolved around the concept of the scientific community and that this concept deserves to be further developed. Moreover, Kuhn acknowledges the term “paradigm” was used in many different ways in the original text but says his intended use of the word is closer to “exemplar.” In other words, normal science proceeds from exemplars, or shared examples that scientists use to understand their field.