This blog post explores the structural significance of normal science, examining how the gradual discoveries accumulated within a paradigm become the foundation for scientific revolution—rather than normal science being merely a period of stagnation.
To explain the structure of scientific revolutions, Kuhn introduced the term ‘paradigm’. A paradigm refers to the widely accepted and orthodox theory among the various theories existing in a specific era and society. For Kuhn, a scientific revolution occurs when one paradigm shifts to the next. A prime example is the shift from Aristotle’s theory of motion to Newtonian mechanics. Aristotle’s theory was long regarded as the best explanation for physical phenomena in that society. However, over time, certain physical phenomena began to emerge that this theory could not account for, leading to a crisis in the existing theory. In this context, Newtonian mechanics emerged, capable of explaining even these phenomena. This new theory replaced Aristotle’s theory of motion and established itself as the new social paradigm. Thus, the structure of a scientific revolution is composed of a series of processes: ‘the emergence of a paradigm – the crisis of the paradigm – the emergence of a new paradigm – the replacement of the paradigm’. Furthermore, according to Kuhn, once a paradigm is fully accepted by society and academia, the period of normal science begins. The period of normal science is the time when scientific activity occurs within the established framework of a specific paradigm. Kuhn viewed the period of normal science as an essential stage in scientific development, yet he also noted in his work that “the period of normal science is one in which scientific development is stagnant.” Upon encountering Kuhn’s ideas, the author determined that the term “stagnation” used to describe the normal science period could be interpreted in two ways: either that science is effectively not progressing, or that scientific progress during this period is gradual rather than as radical as paradigm shifts. Therefore, this essay will examine the reasons each of these two perspectives can be valid, then explore how Kuhn’s concept of scientific revolution can be most clearly explained.
The first perspective on the statement “scientific development is stagnant” during the normal science period interprets it as meaning that no substantive scientific progress occurs. Kuhn describes the period of normal science as simply a stage of solving puzzles. Examining the various experimental tools and laws developed within established large-scale paradigms—such as modern astronomical theory, electromagnetic field theory, and Newtonian mechanics—reveals scope for applying this perspective. For instance, the motion of celestial bodies is explained within the paradigm of contemporary astronomical theory. Accordingly, scientists strive to reorganize experimental tools during observation to conform to the paradigm or adjust laws to fit precisely within the paradigm’s structure. Even the law discovered by Boyle—that “at constant temperature, the volume of a gas is inversely proportional to its pressure”—can be seen as merely designing experimental apparatus within the paradigm of gas molecular motion and then simply interpreting the results. Synthesizing these examples, scientific activity during the period of normal science can be understood as a process of reinforcing an existing paradigm and meticulously organizing its structure. It may appear as a repetition of simple interpretations revealing what the paradigm inherently implied.
Conversely, another perspective on the notion that “scientific progress stagnated” during the period of normal science is that scientific development, while not occurring as radically as a paradigm shift, steadily progresses in a gradual form. A representative case supporting this perspective is the transition from Ptolemy’s geocentric model to Copernicus’s heliocentric model. Ptolemy’s geocentric model, positing that celestial bodies revolve around the Earth, served as the dominant paradigm in astronomy for approximately a thousand years, from the 200s to the 1400s AD. However, during the period of normal science, as various research accumulated using the paradigm as a standard, new facts began to be reported that were difficult to explain within the existing paradigm. These included Galileo’s observations of Jupiter’s moons, Venus’s phases beyond the crescent shape, and the annual parallax of stars. As such research findings increased, the geocentric paradigm gradually declined, ultimately leading to a paradigm shift toward Copernicus’s heliocentric model. These examples clearly demonstrate that scientific activity during periods of normal science is by no means meaningless. Rather, it transforms the structure of science through gradual development, and the accumulated results form the foundation for radical change—the paradigm shift.
So, from what perspective should Kuhn’s statement about stagnation in scientific progress be understood to most clearly interpret his structure of scientific revolution? Rather than choosing just one of two perspectives, I believe we should interpret them by compromising between them depending on the situation. That is, the concept of scientific progress must be understood differently according to the specific circumstances and nature of the facts. For example, suppose two new quantitative laws emerge within a single paradigm. If one of these laws supports the existing paradigm, this can be interpreted as merely confirming facts already implicit within the paradigm, thus not constituting scientific progress. Conversely, if the other law points to a contradiction within the paradigm or raises potential objections, it can be regarded as a theory that cracks the paradigm. If such laws cannot be explained within the framework of the existing paradigm, the paradigm suffers a blow and faces a crisis. As this type of theory and evidence accumulates, the pressure on the paradigm grows, ultimately creating the conditions for a shift from the old paradigm to a new one. In other words, the emergence of theories that crack the paradigm can be interpreted as ‘gradual development’ within the period of normal science, and these gradual developments ultimately connect to lead to radical development in the form of a paradigm shift.
As outlined above, the author views Kuhn’s statement about the “stagnation of scientific progress” as open to two distinct interpretations: first, that scientific progress does not occur; and second, that scientific progress accumulates gradually, though not as radically as a paradigm shift. Subsequently, the author considered how to understand the concept of scientific progress proposed by Kuhn in a way that most effectively explains the structure of scientific revolutions. As a result, the author proposed a compromise interpretation: applying the first perspective to theories that support the paradigm, and the second perspective to theories that can crack the paradigm and induce crisis. Viewing scientific activity during periods of normal science through this integrated lens allows for a more precise and persuasive understanding of the structure of scientific revolution as described by Kuhn.
