Popper vs. Kuhn

Highlighting the differences and drawing conclusions from two giants of the science of philosophy.


7/23/20238 min read

Thesis Statement: Popper and Kuhn’s Theories do not exclude each other, they complement each other.
2000-2500 Words

In the modern philosophy of science debate, there are two names that always come up - Thomas Samuel Kuhn and Sir Karl Reimund Popper. These men are notorious for their contribution to philosophical science. Over the years, since both works were published, „The Structure of Scientific Revolution“ by Thomas Kuhn in 1962 and „The Logic of Scientific Discovery“ by Karl Popper in 1934, there were a lot of discussion about which theory holds supreme. As a result, people divided themselves into different camps - „The Popperians“ and „The Kuhnians“.

In my essay, I will try to show that these two concepts do not necessarily exclude each other. On the contrary, they complement each other. But before we can start with the comparison of these concepts, we need a sophisticated understanding of what these concepts and discussions are about.

Popper's main interest in the philosophy of science was to distinguish between science and non-science, or as Popper called it pseudoscience. In order to solve the problem of demarcation, he develops the theory of falsification. A hypothesis, for Popper, is only scientific if and only if it has the potential to be refuted by some observations. If a theory takes no risk at all or is not bold enough, because it is compatible with every imaginable observation, then it is not scientific. For instance, Einstein's Theory of Relativity was easily refutable by observation but did stand the test. In comparison to Freudian psychoanalysis, Freud could have always verified their hypothesis without being exposed to any risk. Freud's justifications could have been drawn out endlessly for their given observation, whereas Einstein's Theory of Relativity would have been falsified in an instant. Pseudoscience is therefore completely immune to any criticism.

In short, Popper’s concept of Falsification would be best summarized as an ever-ongoing conjecture and refutation.
Popper also claimed that it is never possible to establish a theory by mere confirmation with observations. Because we can never be sure if a theory is true, we can only say that it is not falsified yet. Poppers, inductive skepticism leads inevitably to the tradition of fallibilism. Fallibilism is to believe that there is no absolute certainty in any empirical theory. Popper even goes one step further and says that we can’t even increase the confidence in the truth when it passes observational tests, we can only „corroborate“ a theory that stood the test of time. With the scientific method, we can only deduce that a theory is falsified or not yet falsified by means of inductive observation. Therefore, are universal statements like for instance, „every swan in the world is white“, hard to verify, but easy to falsify if we find one black swan. To summarize the concept of falsification, science needs to make bold conjectures and hypotheses in order to be refuted by testing the hypothesis.

Kuhn on the other hand was more interested in scientific development over time.
The traditional view of scientific development is that science develops straightforwardly by adding new truths to the stack of truths. The scientific method guarantees this progress, whereas great scientists, like Newton or Einstein, can accelerate the progress.
Kuhn heavily disagrees with this notion of scientific development. He thinks that science oscillates between two key stages - „Normal Science“ and „Revolutionary Science“.

Normal Science can be understood as a paradigm. It has its own laws, theories, approaches, ways of applying them, instruments, machines, a network of assumptions, facts that all work together, and a model or a pattern. Therefore, a paradigm or also called the map or disciplinary matrix constitutes itself on facts (e.g. acidity levels), instruments that can measure these things, and their own problems that should be solved. It is also less dramatic than Revolutionary Science and more cumulative in the traditional sense. In normal science, Kuhn claims, everything is about puzzle-solving like solving a jigsaw puzzle. Puzzles assume to have a solution based on that collection of theory, facts, and machines. These assumptions direct the puzzle-solving, and therefore the particular set in the paradigm will solve the puzzle. But sometimes they cannot solve the puzzle, and this leads to anomalies in the disciplinary matrix. If these anomalies are becoming more often, the paradigm will undergo a crisis. This crisis leads to the search for a new paradigm and the advent of revolutionary science.
Revolutionary science or what is also known as a paradigm shift is not like normal science cumulative, but instead involves a revision of the existing scientific belief. In a paradigm, the main theories of the disciplinary matrix are not questioned or contested. However, through the crisis in revolutionary science, they are. This pre-paradigmatic state is like the wild west. There is a lack of consensus, a storm of experimentation, and a competition of schools of thought. Kuhn noticed that these paradigm shifts are usually sparked by eccentric, creative scientists new to the field. Especially if you are new to the field, you are not as subsumed into this assumed paradigm as the older generation. However, what Kuhn also noticed and emphasized was that real progress in normal science is also possible. The requirement for this nevertheless is a strong scientific community with shared values, instruments, and techniques built on top of a disciplinary matrix. For Kuhn, revolutions are not necessary in order to progress in science. It also can put progress on hold. Through the lacking consensus, there is too much arguing on fundamentals instead of developing a research tradition. A paradigm has three main functions for sufficient progress. First, it creates new puzzles, then it suggests approaches to solve these puzzles and last but not least the quality of a proposed puzzle solution can be measured because we have a standard to hold to.
In addition to the alternating phases, normals science, and revolutionary science, Kuhn builds on top of that the concept of incommensurability.
In the traditional empiricist view, you could compare theories without any problems. However, Kuhn believes that theories are essentially incommensurable because they are dependent on the given paradigm. If you compare two theories from two different paradigms, you run into the problem of lack of a common measure. This sparked a whole debate because Kuhn opened with the concept of incommensurability the doors to relativism. If there are no objective interpretations of the world and these are always dependent on the given paradigm, you just end up with interpretations relative to the disciplinary matrix.

By drawing out these key concepts, falsification and paradigms, we can now observe the differences and similarities between the philosophies of Kuhn and Popper better.
Kuhn writes in his essay „Logic of Discovery or Psychology of Research?“ about Popper that they have a lot in common. First and foremost they are both concerned with processes, they both reject accumulation, they support replacement, they value the role of failure and of course are both against the positivists, which sought a neutral objective language.

Regarding the differences, the first distinction between Popper and Kuhn is, that, in Popper’s view, revolution should be sought. This is very similar to the traditionalist view, that revolutions are something positive and should therefore be promoted. Popper would just add, that it is not for the positive knowledge we could potentially gain, it is because of the addition of the negative knowledge. Whereas Kuhn rejects both views and emphasizes that revolution is not a necessity, and we should embrace the progression in normal science.
Secondly, for Popper, is a single anomaly enough to refute a theory. Whereas in Kuhn’s understanding, during the period of normal science, scientist neither seek nor test to confirm guiding theories of their disciplinary matrix. Just one anomaly does not equal falsification. On the contrary, if it is just one anomaly, the scientist who undertakes the experimenting and testing is blamed. These anomalies are often also mostly ignored or explained away. But if this happens again and again and again, even under the best scientist, this would lead to crises in that particular paradigm and therefore to revolutionary science. If a scientist makes a hypothesis in the given paradigm, and it passes the test, the puzzle was solved. But if the puzzle is not solved, the individual would be blamed. The Popperian refutation comes only to life in revolutionary science, where we discard one paradigm for another. In short in normal science the individual is tested, not the theory of the paradigm.
Thirdly, Popper claims that, the revolutionary overthrow of a theory is one that is logically required by an anomaly. Here also, Kuhn begs to differ. There are no rules for deciding the significance of a puzzle. It is an equation with many variables, competing ideas, rational disagreements, and even socio-political influences.
Another point where Kuhn distinguishes himself from Popper is that science is not a philosophical debate. Philosophers work with arguments and objections. Popper does this with his „Theory-Falsification-Theory“-Concept. It is precisely the abandonment of critical discourse in exchange for puzzle-solving which constitutes science. Philosophers can question everything. Scientists can question only within the boundaries of the disciplinary matrix. The only time when scientists become or act as philosophers is in moments of crisis.
And last but not least, we do not need falsification in order to demarcate, so Kuhn. It is not about how for instance astrologers make the prediction nor how they explain every failure away since this also happens in real science. For instance, in medicine, there are so many ways to twist the narrative and explain everything away by simply stating that there are too many variables in order to know if the medicine actually works. However, we can also demarcate by puzzle-solving. Without rules for puzzle-solving, they had no puzzles to solve. Astrologers for instance make predictions that are testable and mailable, but they don’t react or value that failure in the same way science does. If an Astronomer fails, the calculations can be checked and old calculations can be re-examined. Scientists at least try to reason why the failure occurred.

However, after this comparison, this begs the question - „Why Popper then?“
First, Popper’s approach to this subject was totally different from Kuhn’s. Not only because they have different backgrounds, but they reasoned differently. Popper did a logical analysis of demarcation and made mostly normative claims - how to ought. Whereas Kuhn did a more socio-historical analysis and gave a descriptive claim - how it is. It is noteworthy that even though they had different starting points, they came to the same conclusions. This distinction is necessary to understand that they don’t exclude each other. Since the Enlightenment, science was thought of as an open process in contrast to the absolute holy scriptures of the bible. However, with the rise of the industrial revolution, science has become a more absolute objective imperative. For example, through genetics, we can deduce that a person is like that and there is no question about it. Popper and Kuhn both fought from different angles of the epistemological spectrum to come to the same conclusions and free science from this ideological view. Without this suppressive imperative, there are no values from science to bound society. Both of them, through their different backgrounds, can be used in different discussions and contexts on their own or complementary.
In addition to that, the theory of falsification was highly influential in the sciences. For instance, the null hypothesis was a product of this concept. Also, the demarcation method works most of the time very well to distinguish between pseudoscience and science.

And last but not least, the philosopher Imre Lakatos expanded on the theory of falsification and combined it with Kuhn’s concept of paradigms. He upgraded the „naive falsification“ to what he calls „sophisticated falsificationism“. By evaluating a theory, the theory is no more the isolated testable theory, but the so-called „research program“ within a series of testable theories. Each research program has „hard core “ assumptions and is surrounded by a „protective belt“ of auxiliary hypotheses. When a thesis is refuted in the research program, the blame is not directed at the „hard core“ assumptions of the program. Instead, it is directed at the protective belt. There is also no ruling paradigm anymore. Just a lot of competing research programs. This new falsification revitalizes the concept of falsificationism and therefore Popper.

Popper and Kuhn’s Theories do not need to be opposed, as often expressed in these epistemological debates. They have different use cases and are more complementary than anything else. One takes a more logical approach, the other a more social-historical approach, with different outputs, but complementary implementations.


Kuhn, T. „The Structure of Scientific Revolution“
Kuhn, T. „Logic of Discovery or Psychology of Research?“ Popper, K. „The Logic of Scientific Discovery“ Godfrey-Smith, P. „Theory and Reality“ Popper, K. „The Logic of Scientific Discovery“ Godfrey-Smith, P. „Theory and Reality“

Bird, Alexander, "Thomas Kuhn", The Stanford Encyclopedia of Philosophy (Winter 2018 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/win2018/ entries/thomas-kuhn/>.
Thornton, Stephen, "Karl Popper", The Stanford Encyclopedia of Philosophy (Spring 2021 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2021/ entries/popper/>. Musgrave, Alan and Charles Pigden, "Imre Lakatos", The Stanford Encyclopedia of Philosophy (Summer 2021 Edition), Edward N. Zalta (ed.), URL = <https:// plato.stanford.edu/archives/sum2021/entries/lakatos/>.