In this blog post, we will compare the theories of two great philosophers of science, Karl Popper and Thomas Kuhn, and consider what science is and how we can explain its nature.
Textbooks are the books that many students use as the basis for their studies. To learn, textbooks should contain only correct content and should be explained in a thorough manner. People naturally accept the content as truth. This is especially true for math and science textbooks. The content of textbooks teaches us the scientific facts revealed by many mathematicians and scientists in the past, so we learn them as a matter of course.
However, before these facts were recognized as truth, we did not know how all things in the world work. Simply put, much of what is written in science textbooks was just one of many hypotheses that were not true until a few hundred years ago. Before these hypotheses were recognized as true, many scientists went through the process of verifying and proving them, and eventually completed various theories that explain the world. We can look at the research they conducted through the history of science and understand the process by which theories have developed.
Some philosophers of science have each put forward different theories about how science develops and what science is essentially. The most widely known philosophers of science are Karl Popper and Thomas Kuhn. The theories they advocate explain what we call science and how it has changed so far, but they have very different views. Popper expressed a critical view of Kuhn’s book at a symposium held by the International Society for Philosophy of Science in 1965. So, which of the two claims is a more accurate description? This article will discuss how the two claims explain science and how science should be explained.
First, let’s examine Popper’s theory. The most basic term Popper uses to describe science is “falsifiability.” Let’s look at some common examples to see what he means by this.
– It will rain in the future.
– The crow is black.
Suppose there are two propositions above. Both propositions can be meaningful to a positivist and are based on verifiability. In the case of the first proposition, all that is needed is to observe that it will rain in the future, and in the case of the second proposition, all that is needed is to find a crow and confirm that it is black. However, the first proposition does not make sense in Popper’s view. The reason is that we cannot disprove the first proposition. A proposition that cannot be disproved does not provide any useful information to us and therefore has no meaning. The second proposition is possible to disprove. Simply find a crow that is not black. If a white crow is found, the proposition can be modified and further developed.
As mentioned above, Popper’s argument is that the criterion for distinguishing between science and non-science should be refutability. Popper said, “It is logically unacceptable to deduce a theory from a statement that has been verified by experience. Therefore, theories are never empirically verifiable.” He argued that the criterion for compartmentalization should be refutability, not verifiability.
In addition, Popper said that methodological decisions in science are inevitable. Here, methodological rules are considered conventions and are described as the rules of the game of empirical science. The supreme rule for determining methodological rules is that other rules of the scientific process must be devised so as not to prevent any statement in science from being disproved. Popper argues that there must be a methodology because if everything other than problems in the natural sciences is meaningless, then the debate over the concept of meaning will also prove to be meaningless. Empiricists were skeptical of methodology because they did not like the idea that there might be meaningful problems outside the field of empirical, experimental science.
Now let’s take a look at Kuhn’s theory. Kuhn refers to the formation and change of scientific theories as “normal science.” Normal science refers to research activities that are firmly based on one or more scientific achievements from the past. The scientific achievements referred to here are called paradigms. When a community of scientists accepts the paradigm that enables their theories and research, they enter the normal science stage, and this normal science has features similar to solving a puzzle. In other words, in the normal science stage, there are set rules like solving a puzzle, and the given problem is solved within those rules. If this continues and a problem arises that cannot be solved within the paradigm, new paradigms different from the existing ones will emerge. Among the new paradigms, those that survive will break down the existing paradigm and be accepted as new, a process that Kuhn calls a revolution.
The existing and new paradigms mentioned above are characterized by impossibility of commitment. Impossibility of commitment is the concept that new concepts or claims cannot be strictly compared with old concepts or claims in the process of revolution and paradigm shift. A typical example is the process of changing the concept of the celestial body from geocentric theory to heliocentric theory. Geocentrism and heliocentrism existed as different paradigms, and the process of changing from geocentrism to heliocentrism can be described as not adding on to the wall of geocentrism, but rather demolishing the existing theory and building a new wall of heliocentrism.
Even by briefly explaining what Popper and Kuhn each claimed, you can see that the two theories have very different perspectives on science. Kuhn focused on how scientific theories are accepted and changed by people, while Popper focused more on whether a theory has scientific meaning. Since the focus is different, it may not be possible to make a clear comparison or determine whether one is right or wrong. However, since both philosophers talk about what science is, it is possible to talk about it.
First, let’s look at the possibility of refutation that Popper talks about. Popper says that science requires that scientific statements be testable, and that propositions that cannot be refuted are unscientific. The crow proposition presented earlier illustrates this well. But what if a scientist cannot refute an experience? The first thing that comes to mind is the part related to thought experiments. A thought experiment is, as the name suggests, an experiment conducted in the imagination, and we cannot directly verify whether the proposition related to the results of the experiment is correct. In other words, the proposition can be said to be empirically impossible to disprove. Galileo’s thought experiment on inertia led to the derivation of a proposition that explains a fact that had already been proven to be correct in theories such as the law of inertia and the law of conservation of energy. We cannot implement this in a laboratory setting, so empirical refutation is virtually impossible. The debate between Bohr and Einstein over the Copenhagen interpretation of quantum mechanics is in a similar vein. Einstein’s experiments to refute this are also thought experiments. In this case, they are practically impossible to implement, even more so than Galileo’s thought experiments. Therefore, it cannot be done empirically and will be impossible to disprove (similarly, it can only be refuted through thought experiments, and it was actually refuted in this way). Nevertheless, no one would say that the two men’s arguments are unscientific. Of course, most scientific theories are falsifiable, so it cannot be said that Popper’s argument is wrong.
Then, what about Kuhn’s normal science? In the case of the thought experiment presented earlier, Kuhn’s theory would treat it as a single paradigm. If the paradigm created by Galileo can be explained as having won over the existing paradigm and established itself as a single theory, then there is no error. So, can Kuhn’s theory be said to be more correct? It is unlikely that this will be the case. To explain this, let’s go back to the field of quantum mechanics. The theory of quantum mechanics can be seen as the emergence of a new paradigm, quantum mechanics, due to the failure of the existing paradigm of Newtonian mechanics in the microscopic world. Quantum mechanics was determined to be the correct theory and became normal science. According to Koon’s theory, the paradigm of quantum mechanics has won over the paradigm of Newtonian mechanics, so it can be said that it has replaced it and formed a new normal science. However, we do not say that Newtonian mechanics is a completely wrong theory, and physics in the macroscopic world is still explained by Newtonian mechanics. In other words, the two theories coexist in the field of physics. Of course, the concept of quantum mechanics has revolutionized the microscopic world, but it cannot be said that it has replaced all existing paradigms.
According to the logic presented above, it is not possible to say which of the two theories is correct. According to the examples mentioned, there are scientific events that are difficult to explain with each theory, and therefore it is difficult to explain the overall aspects of science. A theory that perfectly explains science should be applicable to all areas of science. However, since the fields of science are very diverse and the examples that appear in each field are all different in nature, it is very difficult to explain everything with one theory. In fact, it is said that current philosophers of science focus more on meta-discourse on individual sciences than on discussions about science in general. Therefore, there will be appropriate theories of philosophy of science for each scientific field, and Popper’s theory or Kuhn’s theory may be one of them. Taking the example given earlier, the development process of science related to thought experiments can be explained by Popper’s theory of normal science, and the development of quantum mechanics can be explained as a process of theory refinement through continuous falsification.
Science cannot be explained by simply one theory. Although the theories proposed by Popper and Kuhn are currently the most widely known and can explain science well, it can be seen that they cannot explain all phenomena. It is also true that each theory can explain the phenomenon well in a specific field. Therefore, I would like to argue that in order to explain science perfectly, we should not think of just one theory, but rather properly combine theories that can explain it well in many situations.
