Bonus Appendix: Kuhn and Science

Mark Mitchell and Janina Jolley

© 2007 All rights reserved.



            Not everyone accepts the idea that science has made successful, steady progress. Most notably, Kuhn (1962) in his book “The Structure of Scientific Revolution,” pointed out that if science progressed step-by-step, newer scientific models of reality would be merely more refined, more evolved versions of older models. But they aren’t. Instead, new models are radically and revolutionarily different from older models. For example, the idea that the earth revolves around the sun is not a refined version of the previous view that the sun revolves around the earth, and Newton’s idea that an object in motion tends to stay in motion is not a refined version of Aristotle’s view that rest is the natural state of an object. Partly to emphasize that scientists’ newer models are so different from older models, Kuhn coined the term paradigm: a lens, conceptual worldview, a model of how the world and science works, a framework, or very broad theory shared by a group of scientists that determines what that community of scientists notice, look for, and study.

            One obvious implication of the newer paradigm being radically different from the older paradigm is that switching from the old paradigm to the new paradigm does not involve taking a small step but instead involves taking a quantum leap. A less obvious implication of the newer paradigm being radically different from the previous paradigm is that the previous paradigm may have little to contribute to the newer one. If the older model has little to contribute to the newer model, scientists may, rather than building on to the previous paradigm, bulldoze it. If scientists bulldoze the old paradigm, all that step-by-step progress made by the old paradigm is also swept away. By pointing out that revolutionary change does occur and by arguing that the steady, evolutionary, routine work that scientists do is swept away during the revolution, Kuhn attempts to lay waste to the textbook-created illusion that science makes lasting, steady progress.

Kuhn did not stop at saying that progress in science occurs by changing from one paradigm to another, what he calls a paradigm shift. Kuhn also argued that scientists,  when deciding whether to leap from one paradigm to another, considered factors other than the evidence.





The problem, according to Kuhn, is that all scientists, rather than being completely open-minded, subscribe to a paradigm. According to Kuhn (1970), scientists need to subscribe to a paradigm because "... something like a paradigm is prerequisite to perception itself. What a man sees depends both upon what he looks at and also upon what his previous visual-conceptual experience has taught him to see. In the absence of such training there can only be, in William James' phrase, a bloomin' buzzin' confusion.” To see what Kuhn is talking about, look at this ambiguous figure. If you don’t have a viewpoint, you can’t make sense of what you are seeing: It’s almost as if you’re not seeing anything.


So, suppose you and your friends have a point of view—you all see the vase. Why do you all see the vase? It could be that some of your unspoken assumptions about the world make all of you see the vase. What would make you give up seeing the vase and see two faces instead? If we told you to look more closely at the dark part of the figure, you would probably still hold to your view that it was a vase. However, if your friends all decided that the image represented two faces, you might change your viewpoint. Similarly, Kuhn believes that the acceptance of a new paradigm is influenced not only by the evidence but also by what influential members of the scientific community believe. One reason he believes that community opinion is important is because he believes that some scientists put their faith in a new paradigm well before the evidence warrants it, whereas others hang on to the old paradigm even after the evidence warrants a move to the new paradigm.

A second reason Kuhn believes that community opinion is so important is because he believes that paradigms cannot be compared based on evidence. Like our vase/faces picture, you can’t say that one paradigm is better than another. According to Kuhn, scientists from two different paradigms can’t, based on the evidence, agree that one paradigm is better than the other because they can’t agree on the evidence: The paradigm determines the evidence and they have different paradigms.

How can paradigms affect what evidence scientists see? The paradigms affect observation because scientists don’t see objects for themselves; instead, scientists see objects as examples of particular concepts (scientists try to put observations into “conceptual boxes”)—and the paradigm determines what those particular concepts are. For example, if your paradigm makes you see the moon as a planet, the moon’s circling the earth is relevant to understanding how the planets move around the earth; if you don’t see the moon as a planet, the moon’s circling of the earth is irrelevant to understanding planetary motion. Thus, evidence that is convincing to followers of one paradigm may be seen as irrelevant or even unscientific to followers of another paradigm.

            Although Kuhn makes some plausible arguments, most scientists disagree with Kuhn’s thesis that the choice of a paradigm is not rational. If paradigms can’t be compared, we couldn’t say that the view that the earth revolves around the sun is a better paradigm than the view that the sun revolves around the earth. If scientists are choosing paradigms for nonrational reasons, either scientists have either have correctly chosen to abandon older paradigms by accident or scientists should go back and revisit rejected paradigms. If scientists from a different paradigm don’t look at the evidence from a rival paradigm, the scientists who believed the sun revolved around the earth would deny the evidence that the earth revolves around the sun. However, people who did believe the sun revolved around the earth changed their minds after looking at the evidence. They did not deny the evidence. Furthermore, research shows that most scientists, regardless of their biases or theories, agree on the basic observations.

            Kuhn, at least at times, seems to agree with the scientists. Kuhn himself has said that science is rational (Haack, 2003), that paradigms can be compared, and that science is not mob rule. Although scholars get frustrated trying to find out what Kuhn really meant (some even complain that there are two Kuhns, a radical one and a moderate one), Kuhn’s impact was determined by what people thought he said. By some standards, Kuhn’s was the first real attack on science—and people may have read more into his attack than he meant. It’s possible that Kuhn merely meant to remind people that science is done by imperfect humans who make subjective decisions (sometimes based on tradition, biases, politics, or funding) about what’s important to study, and who come up with explanations that, although seeming to be true at the time, will later be replaced by a different explanation. If so, Kuhn is like the farmer who prayed for rain and got a flood. Kuhn’s book led to a flood of criticisms of science. Given that almost all criticisms of science owe something to what people thought Kuhn said, let’s use an analogy to understand what many people consider to be Kuhn’s view of science.

                              In this analogy, scientists are like people exploring a dark cave. At first, the explorers make no progress because they can’t see anything. Eventually, however, someone devises a helmet that allows the explorers to see. The problem is that the helmet doesn’t just light up the cave: The helmet highlights some objects, filters out the color of other objects, and completely filters out sounds.

      Given that the explorers started out not seeing or hearing anything, the original explorers don’t see any problems with the helmet. As they teach their followers about how to use the helmet, they also enthusiastically tell their followers stories of people making great discoveries using the helmet. The new group comes away with appreciation for the helmet and a desire to use the helmet to make even more discoveries.

      The new group members are not a bunch of skeptical, independent, creative “out of the box” thinkers. Instead, they are happy to work within the paradigm’s box. Like a family physician, they are skilled at applying what they know to new cases. Put another way, if you think of science as a game, you can think of working within a paradigm as working on a crossword puzzle that has some of the entries already filled in—all you have to do is follow the clues and fill in the remaining entries. Note that you can do very well in this puzzle-solving task without being an independent, skeptical thinker. Indeed, accepting other people’s entries can help you solve the puzzle faster—as can not doubting the validity of the clues.

      To go back to our cave analogy, imagine that the cave contains many objects shaped like cylinders but that the helmet (the paradigm) limits the explorers to looking directly down on the tops of the cylinders. Consequently, instead of seeing these objects as three-dimensional cylinders, the explorers see the objects as two-dimensional circles (see the next figure)[1].








Reality                          Old model of reality                   New model of reality

                                    (View from side)                                   (View from top)                                   

Figure 1-3: Reality is many-sided; a fact that simple, one-sided models do not capture.



As long as the explorers focus on the tops of the cylinders, the explorers will feel they are making progress in better understanding and mapping these objects. Although they run into evidence that counters their “circle view” (they bump into the sides of the cylinder; the circle seems to float; and they hear sound echo off the cylinder), they dismiss that evidence. For example, they may claim that the sides are not part of the circle (or at least not a part worth studying), the apparent floating is due to measurement error, and that hearing echoes in a cave is not a scientific way to study objects. As long as all the investigators—by examining events that fit the model while ignoring events and findings (anomalies) that do not fit the model—go along with the main viewpoint, the investigators appear to make steady progress. Without dissent, investigators may believe they are being objective when they are really under the influence of a paradigm—and that shared paradigm determines both what should be studied and how it how it should be studied.

      As time goes on, the problems with the old paradigm become increasingly obvious. Yet, despite the old model’s problems, the people who have been working on the old model all their professional lives, the people who have become famous by telling people how well the model explains reality, are not willing to give up on the old model.


      Younger investigators who have not invested much of their life on the old model may notice flaws in the old model. If a strong leader urges them to abandon the old model and replace it with the leader’s new model, these younger investigators may follow this rebel leader. To go back to our cylinder analogy, let’s assume that a younger group of cave explorers focus on one of the cylinder’s sides and decide that the cylinder is nothing like a circle, but instead is just like a rectangle. Unfortunately, the new paradigm does not represent as much progress as the rebels believe for two reasons.

      First, the rebels’ eagerness to destroy the old model leads to their abandoning, denigrating, and denying some of the knowledge discovered when people based their investigations on the old model. By saying that the cylinder is nothing like a circle, they lose all the knowledge gained from earlier investigations of the cylinder’s top. By throwing out not just the old model but also the research that was done on that model, the rebels are, in a sense, throwing the baby out with the bathwater.

                   Second, by saying that the cylinder is just like a rectangle, the rebels’ model is still a flawed, oversimplification of reality. Instead of adding to the old, oversimplified (circle) model to make a more complicated, complete, and accurate (circle and rectangle) model, they have replaced it with a new, oversimplified, and flawed model.

      Although the new model may be as flawed as the old model, politics—or, in some cases, mob rule—may allow the rebels to get others to join them in rejecting the old model and replacing it with their new model. To succeed, the rebels will probably need a charismatic leader who has good political skills. The rebels will make persuasive speeches, write persuasive articles, praise their followers, and condemn their opponents. Once in power, the rebels will use their political power to make it easy for their followers—and harder for their opponents—to get grants, publications, honors, and jobs.





      As we hope you can see from our analogy, many people see Kuhn as objecting to the view that science is an unbiased, apolitical, steady march toward objective truth. Many feel that Kuhn has shown that science is political: Scientists, like junior high students, claim to be skeptical and independent but are really trusting and wanting to be popular with the coolest group.

      Scientists point out two problems with the argument that Kuhn’s research on paradigms shows that science is political. First, Kuhn’s finding that paradigms have serious flaws does not prove that scientists are political. To the contrary, the only reason people know about the flaws in paradigms is that scientists found those flaws. Thus, rather than being conforming political animals, scientists, by being skeptical and by making testable predictions, correct their own errors, and avoid being overly committed to an erroneous paradigm.

       Second, Kuhn’s finding that scientists do not all adopt the new paradigm at the same time does not prove that political pressures were at work. Indeed, we would not expect independent scientists to change to the new paradigm all at the same time. Just as reasonable, independent minded people might differ in terms of whether to rebuild or relocate after their neighborhood was damaged in a storm, independent, skeptical scientists could differ in terms of how certain they needed to be before abandoning one paradigm for another.

      Some cynics, in addition to seeing Kuhn’s work as supporting the idea that science is political, also see Kuhn’s work as supporting the idea that scientific progress is an illusion. They see the illusion of progress as the result of a new, inaccurate viewpoint replacing—rather than building on—the old viewpoint.

      Scientists also object to the suggestion that Kuhn’s work shows that scientific progress is an illusion because in every case of a paradigm shift, the shift has been toward a more accurate model. For example, the model that the earth revolves around the sun is more accurate than the model it replaced—the model that had the sun revolving around the earth. As a consequence of newer, better paradigms replacing older paradigms, chemistry, biology, and physics have made tremendous progress over the past 500 years. Thus, although scientists concede that their models are not perfect, scientists point out that their current models are more accurate than either older models or common sense.

Whereas many scientists have dismissed the claims that science is political and that science does not really progress, some critics of science have extended both of these claims. In extending the idea that science is political, some have argued that science is affected by society’s politics. Specifically, some critics view science as a political tool that makes one group’s viewpoint seem true. For example, the Nazis attempted to discredit physics by calling it the “Jewish physics” (Haack, 2004). Similarly, a few feminists have attempted to discredit traditional science by calling it a “male viewpoint” (Haack, 2004).

In extending the idea that science does not march toward objective truth, some have argued that there is no objective truth—only different viewpoints[2]. In terms of our cave-cylinder analogy, their argument would be either (a) that there is no cylinder or (b) that there is no way to objectively describe the cylinder—any description would be colored by one’s biases.

                              Contrary to the cynics, most people agree that (a) there is a real world (see the next figure) and that (b) science is the best, and the most objective, tool we have to understand that world. Almost everyone would agree that science has allowed physics, chemistry, and biology to progress at a rapid rate. Hardly anyone would argue that we could make more progress in understanding our physical world by abandoning science and going back to prescientific beliefs and methods, such as alchemy or philosophy (Dawkins, 1998). Indeed, it seems like every field  ww wants to be labeled a science—from creation science to handwriting science to library science to military science to mortuary science (Haack, 2003).



Rejecting objective facts is not just unscientific: It may be hazardous to your health.




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[1] The idea for this figure was taken from David G. Myers (2002) general psychology text. Myers used the figure to emphasize the complementarity of different levels of analysis. Our purpose here is quite different.

[2] The idea that truth is relative is popular in our culture. However, the idea that there are two valid sides to every story (e.g., the sun exists and the sun never existed) and that either both are true (e.g., the sun exists and the sun never existed) or that the truth lies somewhere in between (e.g., the sun alternates between existing and never existing) is probably not always true. Some point out that a “one-sided” view (e.g., the sun exists) would be more true. To think about relativism another way, the statement “All truth is relative” can’t be objectively true because the statement is an example of a universal (nonrelative) statement about truth. We thank Dr. Jamie Phillips for this example.