PARADIGM.

Paradigm is the key term in Thomas Kuhn's (1922–1996) very influential book, The Structure of Scientific Revolutions (1962). As is frequently the case when new ideas are presented, Kuhn took an existing term and gave it a specialized meaning. The term paradigm now occurs frequently in every kind of discourse, usually to mean something like "way of thinking" or "approach to a problem." Kuhn has generally been given credit for introducing this usage, but the way that paradigm is popularly used misses a central aspect of his argument. Kuhn emphasizes that a paradigm cannot be reduced to a set of beliefs or to a list of rules and indeed that a paradigm cannot be put into words. Scientists have to learn by doing, both by thinking in terms of the concepts that are used in a particular science and by physically manipulating material to create phenomena.

Kuhn argues that the history of science is best understood as exhibiting stable periods, which he calls normal science, punctuated by revolutionary changes. Paradigm is the central concept that Kuhn uses to make his case, since a period of normal science is defined by its paradigm and a scientific revolution is, in Kuhn's terms, a change in paradigms. Typically a paradigm is first established by the publication of a ground-breaking book that sets out problems and solutions, then others adopt the aims and methods of the original, thus establishing a period of normal science. Contrary to the traditional view that science was founded in Renaissance Europe by "the scientific revolution," Kuhn sees multiple revolutions in the history of science, that is, multiple cases of the overthrow of one scientific paradigm by another.

Paradigm is defined in the Oxford English Dictionary as a pattern, exemplar, or example. Kuhn acknowledges this meaning by giving the conjugation of a regular Latin verb as an example of a paradigm. Furthermore, since he believes that a normal science is typically established by an important book and often by a series of experiments, it is clear that Kuhn has the idea of a paradigm as a pattern that will be followed very much in mind when he is explaining his view. A key aspect of paradigms is that they set out problems and also show how to solve them. Newton's laws of motion and the force of gravity combine to explain planetary motion, for example. There is more to a paradigm than a good model to follow, however. Kuhn also thinks that among scientists who are working under the same paradigm, the historian can find common methods, common standards, common aims, and fundamental agreement about the nature of the world and the nature of the processes in it. Periods of normal science are characterized by consensus, especially about fundamentals, and this agreement allows for specialization, or as Kuhn puts it, "professional and esoteric work" (1996, p. 23). The function of normal science is to extend the original work by applying its methods to new areas as well as to revisit old ground in order to refine the paradigm. Because normal science is based on agreement and has well-defined parameters, it can make progress and accumulate knowledge.

On Definition

Kuhn compresses his discussion of the centrality of the notion of paradigm into a single chapter entitled "The Priority of Paradigms." Paradigms have priority because there is nothing more basic by which "paradigm" could be defined. In logical terminology, the word paradigm functions as a primitive term. Properties of paradigms can be given and examples of paradigms can be enumerated, but the word cannot be defined, any more than number can be defined in arithmetic. Kuhn justifies his introduction of the term paradigm by arguing that, for the historian, it is a better organizational concept than any other. By looking for paradigms and changes in paradigms, the historian can classify scientists and historical periods in ways that lead to productive research and a better understanding of the history of science. Turning to philosophers to justify the undefinability of paradigms, Kuhn invokes Michael Polyani's (1891–1976) idea of tacit knowledge and Ludwig Wittgenstein's (1889–1951) idea that some human activities cannot be captured by a set of rules, arguing that while paradigms cannot be reduced to a set of methods and beliefs, they are recognizable to the historian as the organizing principle underlying a period of normal science.

The root definition of paradigm as both pattern and example exhibits both sides of a classical philosophical debate over the nature of definition. Plato (c. 428–348 or 347 b.c.e.) argued forcefully that providing examples is not adequate; the real definition of a term must specify what the examples have in common and thus explain why they all properly fall under the concept being defined. In the terminology of later philosophy, Plato argues that a definition must tell us the essence of a thing. For Plato, this is the eidos, the eternal form or idea to which all objects falling under a concept must conform. Kuhn sides with David Hume (1711–1776) and Wittgenstein in rejecting Plato's requirement that the essence be given in the proper definition of a concept. Like Hume, Kuhn argues that it is enough to say that the objects falling under a concept resemble one another in various aspects that can be specified and to take that resemblance as a starting point. Kuhn claims that paradigms do not have an essence, since there is always some disagreement and some difference in emphasis among scientists who are working under the same paradigm. In Wittgenstein's terminology, the historian can find a family resemblance among the views of these scientists rather than single common set of beliefs and methods.

Kuhn also defends his view that paradigms cannot be reduced to a set of beliefs and rules of method by pointing out that scientists learn by working through concrete examples of problems, not by learning rules. Thus learning a paradigm is more like learning a skill than like learning a body of knowledge, a point that Joseph Rouse has rightly emphasized. Kuhn is very close to using paradigm in its original meaning here, since the problems and solutions through which students learn are to be taken as patterns of scientific thought and work.

Criticism of Kuhn's Paradigms

Kuhn's use of the term paradigm was immediately criticized, especially by philosophers, for being too broad and vague. In the postscript to Structure (1962), Kuhn conceded that the term was perhaps too broad, saying that he would use paradigm to mean "exemplar," that is, the founding book or experiment of a particular science, and that the rest of the elements that make up normal science will be called the "disciplinary matrix." However, this change in terminology played no role in Kuhn's later work, so it provides little gain in understanding his viewpoint.

Kuhn was also accused of circularity, since it seems that in order to determine the nature of the paradigm behind a particular period of normal science, the historian must first determine which scientists belong to that group and then study their work to discover their aims, methods, and assumptions. However, since normal science is defined in terms of a paradigm, it seems that the historian must also recognize a paradigm first in order to know which scientists are working under it. Kuhn acknowledged that this was indeed a problem, suggesting that scientists should be categorized first on purely sociological grounds, such as who works with whom, and then the paradigm that underlies these connections be can determined.

Revolutions

Kuhn argued that his use of the term revolution to describe changes in science is appropriate because, like political revolutions, scientific revolutions overturn existing rules and institutions in order to establish new ones. By definition, there can be no legal way to have a political revolution, since any changes that follow the processes of the old regime would merely be reform, not revolution. For Kuhn the key point of the analogy between political and scientific revolutions is that in both cases there are no rules that could help adjudicate between the two systems. The supporters of the old and the new paradigms will each follow their own methods, emphasize their own aims, and accept their own solutions to problems, without necessarily accepting any of the methods, aims, or standards of supporters of the other paradigm. In an influential paper that helped redirect criticism of Kuhn's book, Gerald Doppelt emphasized the apparent relativism of Kuhn's view, given that there is no right or wrong answer to the question of when an old paradigm should be abandoned and a new paradigm adopted. Antoine-Laurent Lavoisier (1743–1794) and Joseph Priestley (1733–1804) independently discovered oxygen, but while Lavoisier used this discovery as a basis for a new chemistry, Priestley never accepted Lavoisier's revolution and maintained the old phlogiston paradigm instead. Kuhn argued that both of these famous scientists were acting reasonably. Nothing can force a scientist to change paradigms, according to Kuhn, because a scientist can always find a way either to incorporate new data into the existing paradigm or to show why the new data can be dismissed as unimportant from the point of view of the existing paradigm. It is important to note, however, that Kuhn is not saying that anyone can believe anything. Paradigms must be well developed and cover a wide range of phenomena. It is not easy to develop a new science that will justify the overthrow of an established paradigm.

Rather than promoting general relativism, Kuhn saw himself as rejecting particular philosophical accounts of science. He criticizes the idea of confirming scientific theories and comparing how well they are confirmed, a view of science associated with Rudolf Carnap (1891–1970), and he criticizes the idea of testing scientific theories to show that one theory is false, a view of science associated with Karl Popper (1902–1994). Both of these views require that a body of neutral evidence be available to scientists, a position that Kuhn disputes because, he claims, all evidence is acquired on the basis of a paradigm and therefore an element of it. He also points out that Popper's view that theories should be rejected when negative evidence is found is unrealistic, since there are always anomalies—problems that the paradigm cannot solve.

Leaps of Faith

Given that no new evidence or argument could overthrow a paradigm, Kuhn needs to explain "What causes the group [of professional scientists] to abandon one tradition of normal research in favor of another" (1996, p. 144). After pointing out that it is possible for a revolution to take place over generations without requiring individual scientists to change from one paradigm to another, Kuhn sets out four reasons that scientists may have for deciding to change paradigms. Two of these reasons, aesthetic considerations (including simplicity, unity, and so forth) and personal or political beliefs, are clearly subjective. We can understand how Lavoisier could have reasons to revolutionize chemistry that Priestley did not share, if the reasons given are personal and subjective. We do not expect others to have the same personal or subjective views or tastes that we do. Kuhn also says that a scientist may change from one paradigm to another if the new paradigm solves problems that the old one could not. New paradigms are successfully introduced when there is a crisis, that is, when scientists feel that the old paradigm is not working. To revolutionary scientists, what had been anomalies are now seen as refutations of the old paradigm. Although this reason for changing paradigms sounds objective, Kuhn argues that there is no objective way to know how seriously anomalies should be taken. Some, like Lavoisier, will feel that there is a crisis and a need for revolutionary change, while others, like Priestley, can look at the same situation and feel no need for change. To add to the sense that these two positions are subjective, Kuhn famously describes the change from one paradigm to another as a Gestalt shift, in which a picture of an old woman suddenly looks like a young woman or a duck suddenly looks like a rabbit. When they are seen from the perspective of the new paradigm, what had been minor anomalous puzzles suddenly show that the old paradigm was terribly wrong. Finally, Kuhn points out that in a revolutionary period, scientists must decide which paradigm is more promising for future success. Such forward-looking predictions are bound to be based on partial information and require belief in the promise of the paradigm. Kuhn calls this a matter of faith and argues that it too is subjective, like all of the reasons that scientists may have to change paradigms.

Criticism of Kuhn's Relativism

Kuhn was rather surprised at the reaction of many philosophers and scientists to his work. He did not see himself as claiming that science is irrational or subjective but rather as developing a philosophy of science that was true to the actual history of science. While this may be true, it is also clear that Kuhn was quite capable of using inflammatory rhetoric that was bound to offend many supporters of science. For example, when explaining the analogy with political revolution, he says that the defender of a new viewpoint must resort to "techniques of mass persuasion, including force" when political recourse fails (1996, p. 93). In the mythology of modern science, the church represents the Dark Ages, superstition, and jargon-filled Scholastic rationalizations, whereas science represents reason, knowledge, and the objective quest for the truth. Yet Kuhn says that science textbooks are as dogmatic as orthodox theology, and, in arguing that there is no objective criterion for deciding between paradigms, he says changing from one paradigm to another is a "conversion experience" (1996, p. 151). Explaining how the existence of multiple revolutions has been covered up by traditional histories of science, Kuhn compares these histories to those given to the population in George Orwell's (Eric Arthur Blair; 1903–1950) 1984 (1949), which is about as far from objective truth as can be imagined. Kuhn also compares science textbooks to tourist brochures.

Incommensurable Worlds

In order to justify his claim that there is no neutral set of observations or experiments that could help scientists determine which paradigm is true, Kuhn argues that the Gestalt experiments show how it is possible to think of a scientist as seeing the world very differently after a change of paradigm. Examples of scientists s eeing different things after a change of paradigm include the following: The earth was seen as the center of the universe, then as a planet orbiting one of millions of stars. Light was seen first as a particle, then as a wave, and finally as a photon. Uranus was first seen as a star, then as a comet, then finally as a planet when William Herschel (1738–1822) "discovered" it. Dephlogisticated air was later seen as oxygen. Stones restrained from falling to their natural place were later seen as the repetitive motion of a pendulum. Kuhn argues that the revolutionary changes described in these examples are not simply changes in the name of something: Phlogiston is not anti-oxygen, the pendulum is not a falling stone, and so forth. Scientists working in different paradigms collect different data and work on different problems. Something that formerly needed to be explained may be seen as natural under a new paradigm, and what seemed natural before may now seem to need an explanation. Therefore "the historian of science may be tempted to exclaim that when paradigms change, the world itself changes with them" (1996, p. 111).

Although he occasionally said contradictory things on this issue in Structure, Kuhn later insisted that the scientists working under different paradigms really do live in different worlds. Paradigms cannot be said to be different interpretations of a single objective world because "interpretation" only happens within a paradigm. We do not see the world as it really is but rather have to learn how to see, guided by the paradigm. Without a paradigm, there would be no science at all; rather there would only be confusion, a point that Kuhn makes with his reference to the experiments of Jerome S. Bruner and Leo Postman with anomalous playing cards and of George M. Stratton with inverted vision. Kuhn introduced the term incommensurability to describe the difficulty of comparing one paradigm to another. There is no way to test a paradigm as a whole or to compare the predictions that derive from paradigms against one another, as scientists do when they test theories. Kuhn argues that in cases where the same word is used in two different paradigms or when it seems that the same phenomenon can be described in both, the words in fact have different meanings in each paradigm and the phenomenon is not the same.

Thomas Kuhn

Thomas Samuel Kuhn was born on 18 July 1922 in Cincinnati, Ohio. He graduated summa cum laude from Harvard in 1943 with a bachelor's degree in physics, and after some work in the government Office of Scientific Research and Development during World War II, he returned to Harvard for his master's and doctoral degrees in physics in 1946 and 1949. He remained at Harvard until 1956 teaching in the Department of the History of Science that had just been created by his mentor James Conant, who aided his transition from theoretical physics to the history and philosophy of science. Kuhn next joined the faculty of the University of California at Berkeley, where he developed the idea for his most influential book. In 1964 he moved to Princeton, where he was the M. Taylor Pyne Professor of Philosophy and History of Science. Kuhn returned to Boston to complete his career at the Massachusetts Institute of Technology as professor of philosophy and history of science from 1979 to 1983 and the Laurence S. Rockefeller Professor of Philosophy from 1983 until 1991. Kuhn was the author or coauthor of five books and scores of articles on the philosophy and history of science. He was a Guggenheim Fellow in 1954–1955, the winner of the George Sarton Medal in the History of Science in 1982, and the holder of honorary degrees from many institutions, among them the University of Notre Dame, Columbia University, the University of Chicago, the University of Padua, and the University of Athens. Kuhn suffered from cancer during the last years of his life and died in 1996.

Revolutions have been covered up by textbooks, whose job it is to teach current science, not to teach history of science. Words are applied anachronistically, and the development of science is made to look linear and cumulative. As a historian, Kuhn discovered that there are radically different ways of doing science. He sought a way of expressing his discovery and of explaining the immersion into a historical text that is required for understanding. The concept of a paradigm is central to Kuhn's expression of his discovery and to his attempt to correct philosophical misrepresentations of science.

See also Knowledge ; Relativism ; Science .

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David J. Stump