Thomas Kuhn’s book The Structure of Scientific Revolutions (1962), introduced the concept of paradigm into the philosophy of science. Instead of conceiving the history of science as a linear process of accumulation, he defends an image in which periods of stability are followed by crises, after which a new paradigm is found.
Scientific change thus also includes a sociological process in which scientific communities accept or reject key assumptions regarding the nature of their disciplines and the types of problems they are interested in.
Who Was Thomas Kuhn?
Before delving into the concept of paradigm and scientific revolutions, it is worth remembering who Thomas Kuhn was. Thomas Kuhn is one of the most influential and relevant philosophers of science of the twentieth century. He graduated in 1943 from Harvard College in physics. He would also obtain a master’s in science and his Ph.D. from the same university in 1946 and 1949, respectively.
Kuhn taught a history of science course that marked the beginning of his growing interest in the way science is produced; this course would eventually lead him to explore the philosophy of science (Bird, 2018). He lectured at Berkeley University, California, in 1956. His colleagues at Berkeley introduced him to the philosophies of Wittgenstein and Feyerabend (Bird, 2018). Other universities where he lectured were Princeton and MIT. Some of his two most prominent books are The Copernican Revolution (1957), and The Structure of Scientific Revolutions (1962). The second book continues to be, without a doubt, his most significant and controversial work. Many of his later contributions, including a postscript in 1969, deal with the concepts introduced in the Structure of Scientific Revolutions.
Paradigms and Normal Science
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In The Structure of Scientific Revolutions, Kuhn explores the history of science to create his philosophy of science. Instead of speculating about what scientists do, he preferred to carefully observe how is it that theories are created and tested, and how communities of scientists establish assumptions and axioms that underpin their research. With this idea, Thomas Kuhn commences his essay:
“History, if viewed as a repository for more than anecdote or chronology, could produce a decisive transformation in the image of science by which we are now possessed”
(1996, p. 1).
From his historical examination, Kuhn discovers a pattern of theory development. The different stages he encountered can be immensely simplified in the following chart:
The preparadigmatic stage is characterized by debates between competing schools within a particular field of science. These schools disagree about which methods of research are the most useful, the questions that require more attention, and the standard procedures of the solution to scientific problems (Kuhn, 1996, p. 47). Consequently, at this stage, there is an absence of a paradigm that encompasses scientific practice; put differently, no scientific consensus has been reached. Normally, this preparadigmatic stage relates to the early phases of any discipline.
The ancient philosophers of the physis (also called the presocratic philosophers) are a good example of this lack of consensus: Thales of Miletus, Anaximander, Anaximenes, and Democritus wanted to grasp the nature of the cosmos but disagreed about the “arche,” that is, the primordial element of everything (Kenny & Kenny, 2004, Chapter 1).
Once methods, problems, and the main axioms are accepted by a large community of scientists, the second phase initiates, that of normal science. Here, research is done under a paradigm; the discipline can be regarded as a mature science (Nickles, 2017).
An abridged version of the term ‘paradigm’ is that it constitutes exemplary pieces of research taken as a guide for future inquiries; they are recognized ways of modeling problems and solutions adopted by a scientific community (Kuhn, 1996, p. 24). The concept also includes what Kuhn later calls “symbolic generalizations”: a bundle of expressions and claims that are employed by the group without the need for justification. The arsenal of exemplary pieces and symbolic generalizations are constituents of a paradigm.
Normal Science actualizes those generalizations by “increasing the extent of the match between … facts and the paradigm’s predictions, and by further articulation of the paradigm itself” (Kuhn, 1996, p. 24).
Normal science, thus, works within the paradigm, with the theoretical and methodological techniques that the paradigm provides. For Thomas Kuhn, the paradigm not only orients theory but also the type of facts that should be highlighted in research (1996, p. 25). To use a metaphor, paradigms are like lenses through which the world is seen and interpreted; some phenomena are highlighted while others are ignored. In this sense, normal science discourages revolutionary initiatives in the field and novel discoveries because these threaten the paradigm (Nickles, 2017).
In his book, Thomas Kuhn uses concepts of Gestalt Psychology to better explain what a paradigm is. Often, paintings and images are used in Gestalt Psychology to explain perception. The main idea is that the image is not being neutrally observed, but rather it is being interpreted. For example, when looking at the famous image of the duck-rabbit (below), one can see two images: a depiction of a duck and a depiction of a rabbit. However, it is difficult to see the two layers simultaneously. Kuhn was fond of this effect in terms of how a paradigm affects the relationship between the researcher and the world she is investigating. The paradigm brings attention to one aspect while obscuring the other. For this reason, a scientific revolution is akin to a change in vision; the scientist “must learn to see a new gestalt” (Kuhn, 1996, p. 112).
We said that a paradigm is made both by exemplary pieces of research (that function as models for future inquiry) and by bundles of assumptions, methods, problems, and ways of solving them. Before Copernicus, the accepted paradigm in cosmology was that of the Greco-Roman astronomer Ptolemy (c. 100 – c. 170 AD). Ptolemy defended a geocentric model of the universe. The Earth was fixed in his model and all celestial bodies moved around it. In a later work titled Planetary Hypotheses, he not only continued to develop his geocentric model but, even more, he provided descriptions of how to build the proper instruments adapted to his astronomical model (Hamm, 2016). This is a great illustration of a paradigm that shapes scientific practice down to the details of instrumentation.
Let us now consider the subsequent stages: crisis and paradigm shifts. The periods of crises in a paradigm begin with the accumulation of anomalies. In the words of Nickles:
“When persistent efforts by the best researchers fail to resolve the anomalies, the community begins to lose confidence in the paradigm and a crisis period ensues in which serious alternatives can now be entertained”
Anomalies are initially explained within the paradigm. In the case of the Ptolemaic model of the universe, anomalies in the movement of the planets had to be clarified. The retrograde motion of the planets (observed from the Earth) lead Ptolemy to argue in favor of a combination of two circulation motions. Nevertheless, this increased the complexity of the theory as a whole.
The Copernican model, in contrast, dissolved the apparent anomaly without the need for increasing complexity. The movement of the earth around the sun (better known as the heliocentric model) easily explained the strange retrograde motion of the other planets. Consequently, scientific revolutions occur when a set of assumptions and theories lose credibility once faced with anomalies.
Anomalies, writes Thomas Kuhn, foster new ways of seeing; that is why he also alluded to revolutions as gestalt shifts (1996, p. 122). During the crisis, other competing schools try to replace the old paradigm. Once a new paradigm has been accepted (In this case the cosmological model of Copernicus) the period of normal science commences. The new paradigm reorganizes many elements of scientific practice: “goals, standards, linguistic meaning, key scientific practices, the way both the technical content and the relevant specialist community are organized, and the way scientists perceive the world.” (Nickles, 2017).
Scientific Revolutions After Thomas Kuhn
There are of course more examples of Scientific Revolutions: Galileo’s work, the transition from Aristotelian physics to that of Newton, or the revolution in biology and evolutionary theory when the goal-oriented model was challenged by Charles Darwin’s natural selection theory. It is essential to keep in mind that Kuhn’s explanation makes sense when looking at the way these revolutions are structured. The scope and applicability of his work partly illuminate why his book remains among the most widely quoted in history.
Kuhn’s theory showed that science is not a linear progress; science does not consist of the historical accumulation of knowledge and facts about the world. This was an idea from the Enlightenment and the positivistic understanding of science (e.g., Comte). The reality of the history of science, on the other hand, draws a picture of cycles between times of normal science and periods of crisis. After a crisis, phenomena that were considered explained become problematic.
This is referred to as the “Kuhn loss,” meaning that solutions found in the older tradition may temporarily disappear or become obsolete (Oberheim & Hoyningen-Huene, 2018) For Kuhn, this is the reason why Newton’s theory was rejected: because it did not explain the attractive forces between matter, something that the perspective of Aristotle and Descartes did provide (Kuhn 1962, p. 148).
Remarkably, Thomas Kuhn’s work had immense influence outside the philosophy of the natural sciences. Those within the social sciences and the critical tradition warmly welcomed the concept of paradigm and scientific revolution. In a long struggle against positivism, social philosophers had adamantly opposed the image of science as a neutral, biased-free enterprise. Kuhn offered a conception of science where the world was not transparent but was always being interpreted from a paradigm. Thus, The Structure of the Scientific Revolutions remains a referent both in poststructuralism and constructivism in the social sciences.
Bird, A. (2018). Thomas Kuhn. In The Stanford Encyclopedia of Philosophy.
Hamm, E. (2016). Modeling the Heavens: Sphairopoiia and Ptolemy’s Planetary Hypotheses. Perspectives on Science, 24(4), 416–424. https://doi.org/10.1162/POSC_a_00214
Kenny, A., & Kenny, A. (2004). Ancient philosophy. Clarendon Press ; Oxford University Press.
Kuhn, T. (1996). The Structure of Scientific Revolutions (3rd Ed.). University of Chicago Press.
Nickles, T. (2017). Scientific Revolutions. In The Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/archives/win2017/entries/scientific-revolutions/
Oberheim, E., & Hoyningen-Huene, P. (2018). The Incommensurability of Scientific Theories. In The Stanford Encyclopedia of Philosophy. https://plato.stanford.edu/archives/fall2018/entries/incommensurability/