What is Science? What is Pseudoscience? Karl Popper’s Solution

In several of my recent posts, I have been discussing the question to what degree science reveals reality. But an even more fundamental question is: “What is science?” It is somewhat ironic to discuss particular achievements or difficulties of science if we are not even clear on what exactly science is. For instance, some confidently assert that (Super)string Theory is not science, but obviously the proponents of the theory would not agree.

So, what distinguishes science from a pseudoscience? In this post, I asked whether Freud’s psychoanalysis really was a genuine science, as he strongly asserted. But I am not the only one who asked these questions. People with far greater expertise have wondered about what exactly it is that distinguishes a genuine from a counterfeit science. One of these great minds was Karl Popper.

In what follows I heavily rely on Jeffrey L. Kasser’s treatment of Popper and the attempt to determine the demarcation line between science and pseudoscience. Go here if you want to get more from Kasser on the philosophy of science.

Karl Popper was especially interested in Einstein’s theory of relativity, Karl Marx’s theory of history, and the psychological theories of Sigmund Freud and Alfred Adler. It was widely believed at the time that the work of Marx, Freud, and Adler was genuinely scientific, but Popper became disenchanted with such theories. He, instead, argued that Einstein’s theory was distinguished from those of Marx, Freud, and Adler by its openness to criticism. This provides the key to Popper’s solution to the problem of demarcation.

Popper’s emphasis on criticism stems from his rejection of the most straightforward criterion of demarcation, according to which scientific claims are special because they are confirmed by observational evidence and because they explain observations.

Kasser explains Popper’s view that pseudosciences, such as astrology, are chock full of appeals to observational evidence. Hence, Popper thought, observation is cheap. It is essentially interpretation of experience in terms of one’s theory. The pseudoscientist finds confirming evidence everywhere (for example, in the many case studies of Freud and Adler).

Furthermore, apparent counterevidence can be turned aside or even turned into confirming evidence by a clever pseudoscientist. Freud and Adler had ready explanations for any observational result. For Popper, no evidence falsifies a pseudoscientific claim and almost everything confirms it. As a result, Popper came to see the two standard virtues of scientific theories as explanatory power and confirmation by a large number of instances as closer to being vices than virtues.

Fitting the data well is, thus, not the mark of a scientific theory.

What, then, is the mark of a good scientific theory? According to Popper, a good scientific theory should be informative, surprising, and in a certain sense, improbable.

Popper saw Einstein’s theory of relativity to perfectly exemplify these three criteria for genuine science. General relativity led to the surprising prediction that light would be bent by the gravitational field of the Sun. It was a great triumph when Arthur Eddington’s expeditions verified that light was bent by the amount that Einstein had predicted. For most observers, what mattered was the fit between Einstein’s predictions and the evidence, but not for Popper. What mattered to him was that the theory had survived a severe test. The mark of a genuinely scientific theory is falsifiability. Science should make bold conjectures and should try to falsify these conjectures.

I could end my post here, but Kasser goes on to stay that though Popper’s theory is admirably straightforward, it nevertheless requires some clarification. First, Popper generally writes as if falsifiability and, hence, scientific standing come in degrees. This suggests, however, that pseudosciences differ more in degree than in kind from genuine sciences. Second, Popper’s theory is both descriptive and normative, i.e. he claims both that this is what scientists do and that it is what they should do. Third, Popper is not offering a definition of science but only a necessary condition. He is not saying that all falsifiable statements are scientific but only that all scientific statements are falsifiable. Falsifiability is a pretty weak condition. Fourth and last, to call something unscientific is not to call it scientifically worthless.

To elucidate the fourth point, Popper thought that Freud, Marx, and Adler said some true and important things, even though he considered their theories unscientific. Furthermore, Popper maintained that metaphysical frameworks, such as atomism (which was not testable for centuries after it was proposed), can help scientists formulate testable hypotheses. Popper even thought for awhile that Darwin’s principle of natural selection was an ultimately unscientific doctrine. He later changed his mind about this, arguing that the Darwinian claim about survival of the fittest is not a mere definition of fitness (and, hence, unfalsifiable) but instead implies historical hypotheses about the causes of traits in current populations.

So far, then, Popper’s views. On to the criticism. Critics of Popper pointed out that statements such as “There is at least one gold sphere at least one mile in diameter in the universe” do not seem to be falsifiable on the basis of any finite number of observations, but they do not seem unscientific either. More important, statements involving probabilities appear unfalsifiable. A run of 50 sixes in a row does not falsify the claim that this is a fair die. Another criticism is that Popper does not adequately distinguish the question of whether a theory is scientific from the question of whether a theory is handled scientifically. Are theories scientific in themselves or only as a function of how they are treated?

Also, there have been several theories in the history of science that at first seemed to be falsified by observed results. But due to the perceived internal coherence of the theory, scientists persisted to experiment until they finally found confirmation for their theory. Should theories be abandoned at the first apparent falsification? This seems to be too rash.

If falsification rather than confirmation is the mark of science, should we accept the idea that being highly confirmed and having wide explanatory scope are not virtues of a scientific theory at all? Was it not a striking feature of Newton’s physics that it could explain the tides, planetary motion, and so on?

Thus, it is not exactly clear how Popper’s view should be expressed: Is it about the logical form of scientific statements or about the way they are treated by their advocates? However it is formulated, it is not clear that it provides a necessary condition for science.