Paradigm Shift

Kuhn’s Definition of Paradigm

Kuhn observed that any developed field in the natural sciences rests upon a body of established theory. In part, this means that a field’s practitioners accept an array of time-tested laws, models, and methods that serve as shared tools for investigating and explaining natural phenomena. But Kuhn emphasized that a body of established theory encompasses a wider range of group commitments as well. In learning to employ the laws and methods that are central to their field, scientists also absorb a specialized conceptual framework, together with a broad set of convictions about what the world is like and about how to practice science. A discipline’s reliance on a body of established theory thus implies a whole network of shared commitments that decisively shape the character of scientific research and education within the field.

As an example of how these group commitments are instilled by scientific training, consider the physics student learning Newton’s second law of motion, typically expressed by the equation f = ma (force = mass × acceleration). What this law means to a physicist, and what a student of physics must learn to understand it, is not adequately captured by this equation alone. A physicist’s grasp of this law includes the ability to apply it to a range of different physical scenarios—that is, to see a variety of different phenomena as manifestations of the same theoretical pattern. Students develop that ability by learning to emulate standard examples that show how the law can be applied to particular problems. Through such training, Kuhn said, scientists acquire a highly specialized and discipline-specific way of seeing: They come to see nature in terms of the theoretical concepts and relationships exemplified in the discipline’s standard examples.

It should be noted that in 1962, when The Structure of Scientific Revolutions was published, paradigm was a fairly obscure word that meant “shared model” or “exemplar.” Kuhn had this established meaning in mind when he first employed the word in his book: He referred to standard examples of a theory’s applications as paradigms to emphasize that such examples serve as shared models for scientists to emulate. In the course of the book, however, Kuhn inadvertently gave the word a new meaning by using it to refer to the entire network of group commitments that underlie a discipline.

Paradigm Shifts

In Kuhn’s view, the relationship between scientific theory and observation is a two-way street. Theory [Page 1201]is informed by and responsive to observed facts, but observation does not occur in a vacuum. What scientists observe is necessarily informed by their disciplinary training. Indeed, every aspect of an experiment—from which instruments are used and how they are employed, to which data are collected and how they are analyzed—is influenced by the conceptual framework and the outlook on nature that a scientist brings to the scientist’s work.

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