Science or Pseudoscience?

Written by Shawn Funk

One of the central issues in the philosophy of science is to identify a criterion of demarcation that distinguishes science from pseudoscience. How are we to know when the systems we use to understand the world are scientific?  Identifying any good reason why something is scientific, while another thing is not, has proved difficult. Karl Popper, Thomas Kuhn, and Larry Laudan are influential philosophers of science who wrestled with this problem during the 20th century.  

Sir Karl Popper proposed that the probability that any theory is true is zero. If we concede that there are an infinite number of possibilities in a general universal theory, the probability is zero because any number over infinity is zero (Curd et al., p. 70, 1998). The implication here is that no number of confirmations to a theory will prove the said theory. Popper thought that if a theory cannot be proved, perhaps it could be refuted. Popper states that “[c]onfirmations should only count if they are the result of risky predictions” (Popper, p. 7, 1957/1998). If a prediction fails, the theory in question is refuted. Popper called this the criterion of falsifiability, becoming, for Popper, the hallmark of science. He states that the “criterion of falsifiability is a solution to this problem [of demarcation], for it says that statements or systems of statements, in order to be ranked as scientific, must be capable of conflicting with possible, or conceivable, observations” (Popper, p. 9, 1957/1998). A theory is, therefore, tentative and can always be refuted through future observations.

Karl Popper cites Einstein’s theory of gravitation as an example of a risky prediction. Einstein’s equations led to the conclusion that gravity bends light. This proposition was later verified by Arthur Eddington’s observations in 1919 by measuring the distance between two stars in the sky at night and during a solar eclipse during the day (Popper, 1957/1998). If the measurements showed equal distance between the same two stars at night and during the day, Einstein’s gravitational theory would have been refuted according to Popper’s program. Einstein’s ‘risky prediction’ was confirmed, and the observations showed a significant change in distance between the two stars indicating that gravity has a bending effect on light, and because his theory of gravitation had predictive power, Popper’s criterion for science was met (Popper, 1957/1998).

The upshot of falsification is that it makes no bones about what is and what isn’t science, the line of demarcation is clear, yet Imre Lakatos and Thomas Kuhn argue that Popper’s criterion goes too far, suggesting that scientists are often unwilling to discard a theory because it failed to predict a novel event (Kuhn, 1970/1998). Lakatos and Kuhn indicate that theories often undergo many transformations to account for failures before they are wholly discarded, especially if there is no ready substitute for the current theory. In other words, scientists work with what they have and are unwilling to let a small hiccup derail their project. Only when problems compound and there is a ready substitute can a theory be refuted (Kuhn, 1970/1998)(Lakatos, 1977/1998).

Thomas Kuhn is careful not to clearly define a demarcation criterion suggesting that “[i]f a demarcation criterion exists (we must not, I think, seek a sharp and decisive one), it may lie just in that part of science which Sir Karl ignores” (Kuhn, p. 14, 1970/1998). So, what did Popper ignore? Kuhn distinguished between periods of extraordinary research and normal science(Kuhn, p. 13, 1970/1998). He argues that Popper’s focus on extraordinary research, that is, periods of conflicting paradigms that incite scientific revolutions (Copernican heliocentrism, Newtonian mechanics, and Einstein’s theory of gravitation) happen very rarely, and to focus exclusively on these moments would obscure how science is normally practiced (Kuhn, 1970/1998).

Kuhn characterizes “normal science” as using accepted theory to solve research puzzles; normal science, Kuhn says, is the “puzzle-solving enterprise” that makes up most scientific research (Kuhn, p. 15, 1970/1998). These puzzles, Kuhn says are like the problems you find at the back of a textbook (Curd et al., p. 67, 1998). For Kuhn, science occurs only after an accepted paradigm of thought has been implemented and practitioners of that theoretical paradigm begin to solve puzzles within the confines of that theory. Kuhn states that “no puzzle-solving enterprise can exist unless its practitioners share criteria which, for that group and for that time, determine when a particular puzzle has been solved” (Kuhn, p. 15, 1970/1998). Normal science requires that every player knows the rules of the game and plays according to rules, makes sense, yet Kuhn is clever here, he says “for that group and for that time”. What of other groups and other times? This poses a problem for Kuhn because he seems to suggest a relativist position, which leaves science hanging in the aether. Kuhn softly indicates that the demarcation criterion might be found in the rational puzzle-solving tradition of “normal science”, yet he fails to ground the notion of “normal science”. Kuhn suggests that the distinction between science and pseudoscience hinges on what a specific group thinks at a specific time, which implies that today’s pseudoscience is yesterday’s science. This conclusion has led many philosophers to characterize his work as relativist (Curd et al., p. 220, 1998). While Kuhn and Popper both make seemingly valid statements about a peculiar character that science has that other knowledge does not, they fail equally to offer any logically conclusive criteria of demarcation.

The demarcation debate takes an interesting turn in 1983 when Larry Laudan publishes an essay called The Demise of the Demarcation Problem where he suggests that

“…philosophy has unequivocally failed to offer up a valid solution to the demarcation problem.”

Laudan emphatically states, “I will not pretend to be able to prove that there is no conceivable philosophical reconstruction of our intuitive distinction between the scientific and the non-scientific. I do believe, though, that we are warranted in saying that none of the criteria which have been offered thus far promises to explicate the distinction” (Laudan, p. 124, 1983). Laudan suggests that all attempts to solve the problem have done more to disprove the idea that there is a definitive line to distinguish between science and pseudoscience. Strikingly, he asserts that the problem itself is no problem at all, but a “pseudo-problem” (Laudan, p. 124, 1983).

The demarcation problem still has no agreed upon solution, yet there is one characteristic that all science shares, that is, progress. Pseudoscientists put up a mirror to the scientific method, starting with a conclusion then working backward to find confirming evidence while negating anything that stands to refute their theory. No progress is made because the pseudoscientists conclusions are preconceived. Confirming evidence, the pseudoscientist will tell you, is “all around us”. If this sounds more like religion than science, you are not mistaken. Scientists use the inductive method to make inferences based on empirical observations; they conduct experiments that test their hypothesis, and in doing so, discover universal laws that lead to scientific progress. Scientists remain skeptical of their findings because the inductive method is not conclusive; thus, they know that their theories are tentative. Perhaps there is no clean way to pin down what it really means to be scientific because the inductive method is itself uncertain. Yes, we want to be certain; we want to take for granted the truth of what we believe, but our inability to define a clear demarcation between science and pseudoscience implies an unsettling thought; that is, uncertainty.  


Curd, M., & Cover, J. A. (1998). Philosophy of science: The central issues. W.W. Norton.

Kuhn, Thomas S. “Logic of discovery or psychology of research?” Philosophy of science: The central issues. Ed. Martin Curd & J. A. Cover, First edition, W.W. Norton, 1998, p.11-19.

Lakatos, Imre. “Science and pseudoscience.” Philosophy of science: The central issues. Ed. Martin Curd & J. A. Cover, First edition, W.W. Norton, 1998, p.20-26.

Popper, Karl. “Science: Conjectures and refutations.” Philosophy of science: The central issues. Ed. Martin Curd & J. A. Cover, First edition, W.W. Norton, 1998, p.3-10.

Laudan, L. (1983, January 1). Larry Laudan, the demise of the demarcation problem. PhilArchive. Retrieved on September 9, 2023.

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