Through the Bohr-Einstein debate, we distinguish between science in the narrow sense (within a school) and science in the broad sense (between schools) in the philosophy of science, analyzing it using Popper and Kuhn’s theories.
In 1927, a debate destined to be remembered in the history of physics unfolded over several days at the Fifth Solvay Conference held in Brussels, Belgium. A sophisticated debate unfolded between Albert Einstein, hailed as one of humanity’s greatest minds, Niels Bohr, the foremost authority on quantum mechanics of the era, and the Copenhagen School aligned with Bohr, centered on the question: ‘Is quantum mechanics valid?’ Einstein pointed out the incompleteness of Heisenberg’s Uncertainty Principle, one of quantum mechanics’ fundamental tenets, through thought experiments. However, Bohr countered by identifying errors in Einstein’s thought experiments. This process deepened scientists’ understanding of quantum mechanics, leading to its significant advancement and eventual maturation into the complete scientific discipline we recognize today.
As seen in this incident and other debates throughout the history of science, scientists adopt dogmatic attitudes within their own schools to defend their theories, but take critical stances in inter-school debates to dismantle opposing logic that contradicts their own theories. This suggests that the nature of ‘science practiced by individuals or small scientific communities (schools of thought)’ (in this case, the Copenhagen school/Einstein individually) is very different from ‘science viewed from the perspective of the entire scientific community, encompassing or spanning schools of thought’ (in this case, the debate between the two schools). Just as the actions of an individual and those of a society possess different properties, the act of science itself exhibits different properties depending on the scope of the actors involved and must be understood within different contexts. However, the philosophical discussions of science presented thus far have failed to distinguish and explain this, and they are insufficient to encompass both types of science with different natures. Therefore, this paper briefly introduces the philosophies of science by Popper and Kuhn, which occupy two axes of contemporary philosophy of science, and aims to analyze and critique which aspects these theories explain and where they are incomplete from the perspective of scientific debate. Furthermore, this paper proposes a new philosophical perspective that analyzes science by distinguishing between science within an individual/school (hereafter ‘narrow science’) and science across schools/the entire scientific community (hereafter ‘broad science’), and presents the rationale for this distinction.
Popper’s proposed process of scientific development can be summarized in one phrase: ‘conjecture and refutation’. No matter how well a theory explains existing experimental results, there is no guarantee it will also explain future observations. Conversely, a single observation that falsifies the theory negates it. Thus, Popper established the conjecture-refutation model to explain scientific phenomena. First, scientists formulate hypotheses to explain phenomena, positing multiple conjectures. To ‘falsify’ these posited hypotheses, various scientific experiments and observations are conducted; theories that are falsified disappear. Conversely, surviving theories, having not yet been falsified, are accepted, but this acceptance is provisional. He viewed this falsification as a defining characteristic of science, citing Eddington’s experiment and Einstein’s theory of relativity as prime examples. From a falsificationist perspective, Eddington conducted an experiment on the properties of light, which Newtonian mechanics and Einstein’s relativity each predicted differently. The result can be interpreted as Newtonian mechanics being falsified, while relativity withstood the falsification attempt and survived.
Popper’s theory effectively explains debates between schools of thought, such as the Copenhagen interpretation surviving Einstein’s falsification attempts at the Solvay Conference, or relativity surviving Eddington’s falsification attempts in the conflict between Newtonian mechanics and relativity. But what about science within a single school? Let’s consider the previous example on a smaller scale. When Einstein presented the results of his thought experiment, the Copenhagen school did not seek errors within the quantum mechanics theory itself but instead looked for errors in Einstein’s experiment. Einstein, too, clung to his long-held deterministic view of science and sought errors in quantum mechanics, which contradicted it. This ‘dogmatic attitude’ cannot be interpreted from Popper’s perspective.
On the other hand, Kuhn’s model of science can be summarized as ‘normal science and paradigms’. A paradigm is a term denoting a kind of scientific norm and the traditions within science that arise from that norm. Furthermore, within the framework of such a paradigm, the activity of uncovering new knowledge through the paradigm’s unique thought processes is called normal science. He likened normal science to solving a puzzle. A puzzle involves 1) solving a specific problem and 2) following specific rules, because the paradigm itself determines 1) what normal science focuses on and 2) how it will conduct its research. Thus, normal science is the work of fitting natural phenomena into the paradigm. However, phenomena that cannot be interpreted by the paradigm gradually accumulate, and once this reaches a certain threshold, a new paradigm is proposed to resolve them. Kuhn argued that this process involves a struggle between the old and new paradigms, leading to a transition to a consensus paradigm within the scientific community. Ultimately, only the victorious paradigm remains in normal science, forming a ‘monopolistic paradigm’.
Kuhn’s theory effectively explains the attitudes of scientists within a school of thought, which could not be interpreted from Popper’s perspective described earlier. Both the Copenhagen school’s process of finding errors and interpreting Einstein’s thought experiment results to fit their paradigm, and conversely, Einstein’s attempt to interpret Heisenberg’s uncertainty principle within his own paradigm, can be understood through Kuhn’s argument. However, it is difficult to use this framework to explain science within the broader scientific community as a whole. Einstein’s deterministic paradigm ultimately succumbs to the Copenhagen interpretation’s quantum mechanics paradigm. Yet, research continues to apply deterministic paradigms like statistical mechanics to sufficiently statistical systems. Furthermore, the ongoing use of science to predict future phenomena demonstrates that we are far from witnessing the dominance of a single paradigm or the disappearance of a defeated paradigm.
We have examined the scope and limitations of Popper and Kuhn’s theories. To transcend these limitations, we propose the following complementary model from Popper, Kuhn, and a pluralistic perspective. First, science in the narrow sense can be interpreted from a paradigm perspective. In his Critique of Pure Reason, philosopher Kant meticulously analyzed the human cognitive system. He argued that when people perceive an event or phenomenon, they do not accept it purely as it is; rather, ‘human cognition creates the concept of the object’ (the Copernican revolution). This can be explained through the relationship between phenomena, categories, and schemas in the cognitive model he proposed. Humans perceive sensations through their senses, analyze them, and view the real world as a phenomenon. This phenomenon is processed and classified through categories—a pre-existing classification system inherent to humans. Schemas serve as the link connecting this empirical ‘phenomenon’ to the categories. For example, consider a person who perceives the sensation of a mosquito bite causing the bitten area to swell. Originally, being bitten by a mosquito and the skin swelling are completely independent phenomena. However, the person places this phenomenon into the ‘cause and effect’ category via the schema, ultimately forming the recognition that mosquito bites cause swelling. Schemas thus play a crucial role in linking experience and perception. Schemata refers to the organic network of these interconnected schemas that ultimately constitutes a person’s cognitive structure.
Kant viewed schemas as a priori, but this claim was later modified by the cognitive development theory proposed by Jean Piaget, a psychologist and philosopher. He explained the relationship between schemas and cognition through assimilation and accommodation. Assimilation refers to the process, similar to Kant’s epistemology, where a person reconstructs and integrates new information to fit their existing schemas. Accommodation, on the other hand, refers to the process where existing schemas change or new schemas are created due to experience. A prime example is how adults, who have more experience than infants, typically perceive the same phenomenon at a higher level of cognition. From this perspective of accommodation, people raised in different environments possess different schemas. From the perspective of assimilation, different schemas ultimately mean perceiving the same phenomenon differently.
Now, let’s examine science in its narrow sense from the schema perspective. Schemata and paradigms share many similarities. For instance, consider the reading process. From the schema theory perspective, reading is a process where the reader reconstructs the meaning of the text presented by the author. The reader’s schema determines 1) which parts of the book to focus on reading and 2) how to accept (or perceive) the meaning. The process by which an individual accumulates knowledge—that is, the process of incorporating new knowledge based on schema—is very similar to the scientific process occurring in normal science, as argued by Kuhn. In normal science, a paradigm dictates how phenomena should be viewed and which scientific methods should be used to solve problems. This mirrors the individual’s process of determining how to perceive phenomena through schema and deciding which elements to focus attention on and accept. This can be interpreted as stemming from the fact that the epistemological process by which individuals acquire knowledge inherently involves building upon an existing structure. In other words, since the very process of accumulating scientific knowledge is grounded in schemata, scientific processes inevitably occur within the framework of what Kuhn termed a ‘paradigm’.
Furthermore, this can be extended to apply to the science practiced by small groups of scientists, or schools of thought. Members of the same school share similar perspectives on phenomena and similar areas of interest. Belonging to the same school implies similar schemata, which ultimately expands the meaning to a group sharing the same paradigm. In other words, science conducted by individuals or within the same school (a group sharing the same schema) can be explained through Kuhn’s paradigms and normal science. This aligns with the stance taken by the Copenhagen school in the Bohr-Einstein debate presented in the introduction and can explain the phenomenon where numerous scientific schools adopt different perspectives to solve different problems.
Conversely, let us interpret ‘science in the broad sense’ occurring across schools and within the entire scientific community. In the actual scientific community, paradigms are not simply explained as Kun claimed—that only the paradigm victorious in competition among multiple paradigms during a scientific revolution survives, while the defeated paradigms disappear. A prime example is Newtonian mechanics. Although Newtonian mechanics was defeated in the scientific revolution by relativity and quantum mechanics in the early 20th century, it remains a well-established paradigm within the everyday range of speeds and masses, and thus persists to this day. This, like the earlier problem raised, does not align with Kuhn’s philosophy advocating for an exclusive paradigm.
Through this, we can observe that within the scientific community, rather than a single paradigm emerging victorious in a scientific revolution as Kuhn proposed, multiple paradigms coexist. In such cases, different paradigms may simultaneously approach the same phenomenon. This can lead to conflicts between paradigms, triggering a process of mutual criticism between schools of thought. This resembles Popper’s process of conjecture and refutation: when scholars with different paradigms propose theories in the form of multiple hypotheses, scientific discussion occurs through mutual criticism at points of conflict. However, unlike Popper’s falsificationism, the key difference is that, in many cases, the points of contact between the paradigms held by different schools are not significant. Therefore, a small part being falsified does not lead to abandoning the entire paradigm. For example, Newtonian mechanics and relativity address different core subjects and aim to solve different problems. Thus, when one theory is falsified, the paradigm itself does not disappear; rather, the paradigm evolves by narrowing the scope where the theory can be applied. This implies that theories within each paradigm act complementarily, leading to pluralism.
So why does this difference arise between science in the narrow sense and science in the broad sense? It is precisely because the schemata people construct throughout their lives are all different. The schemata discussed here encompasses not only simple scientific knowledge but also worldviews—perspectives on the world—and scientific philosophies. Structuralist theory asserts that human attributes are not inherent characteristics but are determined through relationships with the surrounding society. In other words, it is a theory that seeks to explain language, humanity, culture, politics, and economics by understanding the structures formed by these relationships. A closer look at structuralism implies that schemata, the knowledge structures inherent in the human brain, can also exhibit significant individual variation due to relationships with the surrounding society. Examining the assimilation and accommodation processes described by Jean Piaget, the structuralist epistemologist mentioned earlier, reveals how an individual’s cognitive framework changes based on experience. That is, within the scientific community, individuals possess diverse schemata. Those sharing similar schemata form ‘schools’ that share a common paradigm, interacting with other schools holding different paradigms. Within this process, the narrow sense of science practiced within a school sharing the same schema attempts to interpret phenomena and define problems according to their own schema, or paradigm. This results in a scientific process similar to the form described by Kuhn. Conversely, science in the broader sense involves exchanges between individuals who do not share the same schema. This necessitates a mutually critical stance, which can be expressed as a compromise between Popper’s falsificationism and pluralism. That is, the reason the existing scientific philosophical perspectives proposed by Kuhn and Popper failed to fully describe scientific phenomena can be interpreted as stemming from their failure to define the scope of shared schemata and their failure to distinguish between science practiced by individuals and science practiced by society, treating them as identical. By classifying scientific activity into narrow science and broad science, it seems possible to overcome these limitations.
Let us examine the Bohr-Einstein debate through this new lens. Einstein grew up learning the deterministic law of the Second Law of Thermodynamics (the law of increasing entropy) and had a strong inclination to predict phenomena through perfect physical laws. This connected to his deterministic worldview (schemata), and he was a scholar of the relativistic paradigm based on the premise that information transmission cannot occur at speeds exceeding the speed of light. Conversely, Bohr had extensive experience with quantum mechanics, having first proposed the quantum model of the atom. This connects to the paradigm (schemata) of quantum mechanics. Within quantum mechanics, the phenomenon of quantum entanglement gave rise to ‘non-locality’ – a phenomenon that appeared to involve information transfer faster than light. Consequently, scholars at the time considered it contrary to relativity. (It has since been proven that meaningful information transfer does not occur faster than light.) Viewed solely as a debate, the Bohr-Einstein controversy represents scientific activity in the broadest sense. This is because two schools of thought, each possessing different paradigms, were sharply confronting and criticizing each other over the points of contact between their schemata (a concept encompassing both the deterministic worldview and the relativity/quantum mechanics paradigm). Conversely, looking inward at the Bohr-Einstein debate as ‘narrowly defined scientific activity,’ one observes a school sharing the same schema engaging in the ‘puzzle-solving’ process Kun advocated to defend its paradigm.
The scientific community, like any society, must distinguish between actions taken from the perspective of the part and those taken from the perspective of the whole; doing so allows scientific activity to be interpreted more effectively. First, narrow science occurring within an individual or small group of scientists—a single school—was analyzed using the similarity between schema theory and the structure of Kuhn’s normal science paradigm. Subsequently, broader scientific activities conducted between groups of scientists (schools) and within the entire scientific community encompassing them were explained by synthesizing Popper’s process of conjecture and refutation with pluralism. Finally, the reason for the difference between these two was explained from a structuralist perspective: schemata differ depending on the environment in which humans grow up, leading to differences in paradigm construction for interpreting phenomena and defining problems. From this perspective, the Bohr-Einstein controversy, a scientific event, was analyzed.
Kuhn’s paradigm is suitable for explaining normal science and paradigms within a school of thought, but it falls short in explaining the current scientific system where multiple paradigms coexist from the perspective of inter-school mutual criticism and pluralism, as seen in the Bohr-Einstein debate. Conversely, Popper’s Conjecturing and Refutation framework effectively explained attempts at falsification between paradigms within the broader scope of scientific activity, but conversely, it contained errors when applied to explaining routine scientific activity within a single school. Therefore, by dividing the scope of the group of actors engaged in science and considering science as both parts and a whole, we can reconcile the arguments of these two great philosophers of science with the pluralistic perspective, thereby viewing modern science from a more rigorous and novel angle.
