Kuhn vs. Popper: Kuhn’s Challenge to PopperBy: Bruce
In my last post on Wheat and Tares, I wrote somewhat glowingly of Popperâs epistemology based on Conjecture and Refutation. In a post on Millennial Star I even went so far as to explain why I felt there were some touch points between conjecture and refutation and the Gospel. To summarize, Popper believes all knowledge of all types growths through a process of having problems, conjecturing solutions to those problems, then refuting those conjectures based on the discovery of new problems. Through this process we âevolveâ our explanations and they improve over time. The end result is increasing verisimilitude â i.e. closeness to reality â of our knowledge. (I note here that this produces increasing verisimilitude without use of induction.)
Now I will consider the strongest challenger to Popperâs epistemology as elucidated by Thomas S. Kuhn, author of The Structure of Scientific Revolutions. Popper and Kuhn are often considered to be two dynamically opposed views of scientific growth that are in struggle for the heart and soul of science. (See, for example, this book here. I have not read it and donât intend to.) In actuality, Kuhn and Popper have far more in common than they have different from each other. But Kuhnâs view of science does ultimately pose a threat to the very concept of Scientific Realism and proposes, in itâs place, a Positivist view of the world as our ultimate reality. 
A Summary of Kuhnâs View of Science
Letâs begin with an attempt to summarize Kuhnâs view of science. I should first warn the reader that what you might think you know about Kuhn may not be accurate. Kuhn is largely misrepresented by his critics. (Always a good sign that heâs on to something.)
Kuhnâs core view of science is that science is broken up into two phases. Plateaus where what he calls ânormal scienceâ takes place and then periods of dynamic change where existing scientific theories and explanations are in upheaval.
During periods of ânormal scienceâ Kuhn argues that the goal of science is not to refute the theories of science, but rather to find ways to explain existing âanomaliesâ in terms of the accepted scientific explanation of the day. Kuhn used the term âparadigmâ (popularizing it outside of itâs original use only in languages) to describe the currently accepted theories. For the periods of upheaval he uses the term ârevolutionâ to intentional invoke a analogy to political revolutions.
At least, in so far as this goes, this seems rather incontrovertible. For example, I have a friend that is a Professor in Physics. When I asked him about his research, he was looking into why the measurements in certain atomic constants didnât quite match the theory. He hoped to find a way to get a more precise measurement and therefore match theory and observation more closely. This is a wonderful example of what Kuhn calls ânormal science.â He is not trying to falsify any theory (though he might end up falsifying his own hypotheses for how to fit observation with theory) but rather trying to fit the theory better to reality.
But Kuhnâs ideas undermine certain long held (and still strongly held) beliefs about science. The first thing that goes out the window is the idea that scientists are primarily trying to disprove their theories. This simply is not true and has never been true. Kuhn argues that Scientists are so deeply committed to the reality of their paradigms that it is difficult and even painful for them to give it up. In fact, many scientists â particularly the oldest ones â sometimes fail to ever do so even after their entire profession has abandoned the old paradigm. 
Kuhn therefore paints a picture of scientists being âapologistsâ for their respective paradigm. In fact, Kuhn argues, scientists are constantly faced with mismatches between observation and theory. This starts from the moment of the theory being created and continues right up until it is abandoned.  Therefore, the old story that scientists are so open minded that they are ready to abandon their theories if it doesnât match observation is not true either. On the contrary, a scientists primary job is to figure out how to fit observation to a theory.  So it turns out that apologetics is one of the most important aspects of true science.
Notice how close this view of Kuhnâs matches the way the Rejectionist community portrays âapologistsâ:
[counterinstances] can at best help to create a crisis or, more accurately, to reinforce one that is already very much in existence. By themselves they cannot and will not falsify that philosophical theory, for its defenders will do what we have already seen scientists doing when confronted by anomaly. They will devise numerous articulations and ad hoc modifications of their theory in order to eliminate any apparent conflict. (The Structure of Scientific Revolutions, p. 78)
In fact, the religious analogy can, in Kuhnâs view, be taken even further. Kuhn believes that, outside of Theology, science is the only human endeavor where âorthodoxyâ plays such an important role. In non-scientific fields, having competing paradigms is the norm. But within fields that we modernly consider science, one of the defining traits is that they have all reached the point of having one and only one agreed upon paradigm. If they did not, we would tautologically not consider them to be science. This âorthodoxyâ is (in Kuhnâs view) as rigorously defended by the âapologeticâ practice of ânormal scienceâ as are religious theologies.
However, we should note here that the above quote from Kuhn does not mean that counter instances or âanomaliesâ cannot eventually result in abandonment of old theories in favor of new ones. In fact, he explicitly states that counterinstances are what eventually lead to crisis and therefore revolution.
In fact, isnât this very similar to Popperâs view of conjecture and refutation? In both Kuhnâs and Popperâs views, observation does eventually play a role in science by creating problems that ânormal scienceâ simply cannot come up with a way to accommodate through more âapologeticâ means. The end result is eventually ârevolutionâ and the abandonment of an old paradigm in favor of a new and better one that solves more problems then the previous one. In this way both Kuhn and Popper agree that growth of scientific knowledge is real and even agree on the broad outline of how it takes place.
Even Popper fully accepts that Kuhn is right that scientists are not objective. Popper (like Kuhn) actually argues that this is a good thing.
âŚmy guess is that should individual scientists ever become âobjective and rationalâ in the sense of âimpartial and detachedâ, then we should indeed find the revolutionary progress of science barred by an impenetrable obstacle. (Myth of the Framework, p. 22)
The reason this is true is because if scientists were âobjectiveâ then the conjecture and refutation process would not function properly across the community.
Since the method of science is that of critical discussion, it is of great importance that the theories criticized should be tenaciously defended. For only in this way can we learn their real power. And only if criticism meets resistance can we learn the full force of a critical argument. (Myth of the Framework, p. 94)
So far Kuhn is not at odds with Popper, despite popular portrayals to the contrary. That the two most advanced schools of scientific epistemology agree on so much ought to give pause to all scientists that reject this more realistic view of science and scientists. It is not true that scientists are primarily trying to disprove their theories and it is not true that science teaches a person to be objective or even that scientific progress requires such objectivity.
Perhaps a bit more surprising is that neither Kuhn nor Popper favor a view of science where science is strictly cumulative (i.e. nothing in the past gets invalidated â not that we arenât gaining knowledge) in growth of knowledge. Kuhn argues using the historical record to back up his view:
Cumulative acquisition of unanticipated novelties proves to be an almost non-existent exception to the rule of scientific development. The man who takes historic fact seriously must suspect that science does not tend toward the ideal that our image of its cumulativeness has suggested. (The Structure of Scientific Revolutions, p. 96)
Later, weâll look at Popperâs acceptance, though modification on this point. But Popper does not deny that scientific knowledge is not cumulative. Rather, one scientific paradigm must give way to another. The new paradigm must largely disprove the old one and therefore destroy it. It is a creative but destructive process. Worse yet, the new paradigm often fails to give answers to questions the old paradigm did. Kuhn uses the example of how Aristotleâs physics explained why particles of matter attracted each other whereas Newtonâs theory did not.
Must a theory of motion explain the cause of the attractive forces between particles of matter or may it simply note the existence of such forces? Newtonâs dynamics was widely rejected because, unlike both Aristotleâs and Descarteâs theories, it implied the latter answer to the question. When Newtonâs theory had been accepted, the question was therefore banished from science. That question, however, was one that general relatively may proudly claim to have solved. (The Structure of Scientific Revolutions, p. 148)
Aristotleâs theory of attraction was that there are four elements â earth, air, fire, water â and they have a natural affinity for each other and that is why, for example, some things fall to the earth and some float. They are finding their natural element that they are primarily made out of.
Before you laugh at this theory, wait for my post where I point out that this is a much better theory that we moderns seem capable of giving it credit for. But for the moment, just accept the key point. Newtonâs theories were deemed a step back in some ways because it failed to answer questions that Aristotleâs theories did seem to answer. Therefore the growth of scientific knowledge was not strictly cumulative.
It was not until Einsteinâs General Relativity that the accepted paradigm once again answered why particles of matter attract. An indirect triumph for Aristotleâs theories in that it turned out that this was a valid question after all and Newtonâs theories were wrong to ignore it.
Kuhnâs Challenge to Popper
But both Kuhn and Popper agree that their two view are, at least somewhat, at odds with each other. Kuhn points out that if this view of science is correct (and remember Popper agrees with the facts so far) then Popperâs view of âConjecture and Refutationâ is (in Kuhnâs view) possibly flawed because, in fact, there is no such thing as âfalsificationâ of theories per se (though there might be of hypotheses meant to support a theory) except between paradigms. Here, I will let Kuhn do his own arguing:
A very different approach to this whole network of problems has been developed by Karl R. Popper who denies the existence of any verification procedures at all. Instead he emphasizes the importance of falsification, i.e., of the test that, because its outcome is negative, necessitates the rejection of an established theory. Clearly, the role thus attributed to falsification is much like the one this essay assigns to anomalous experiences, i.e., to experiences that, by evoking crisis, prepare the way for a new theory. Nevertheless, anomalous experiences may not be identified with falsifying ones. Indeed, I doubt that the latter exist. As has repeatedly been emphasized before, no theory ever solves all the puzzles with which it is confronted at a given time; nor are the solutions already achieved often perfect. On the contrary, it is just the incompleteness of the imperfection of the existing data-theory fit that, at any time, define many of the puzzles that characterize normal science. If any and every failure to fit were ground for theory rejection, all theories ought to be rejected at all times. (The Structure of Scientific Revolutions, p. 146)
Popperâs anomalous experience is important to science because it evokes competitors for an existing paradigm. But falsification, though it surely occurs, does not happen with, or simply because of, the emergence of an anomaly or falsifying instance. Instead, it is a subsequent and separate process that might equally well be called verification since it consists in the triumph of a new paradigm over the old one. (The Structure of Scientific Revolutions, p. 147)
Therefore the real difference between Popper and Kuhn (in Kuhnâs mind anyhow) is that Popper disbelieves in âverificationâ and Kuhn points out (correctly in my opinion) that âfalsificationâ only takes place once a crisis is reached and a revolution is underway. At this point we are always comparing theories and explanations. Therefore âfalsificationâ through observation is identical to âacceptance through verification.â Popper is thus wrong on one point. Verification does, in a certain sense, exist.
Note, however, that Kuhn does not deny that âfalsificationâ not exist at all. Therefore, even this quote above is not a direct attack on Popperâs epistemology because Kuhn does accept falsification in the case of comparison between paradigms. (Though Kuhn prefers to think of it more straightforwardly as verification rather than falsification.)
Kuhnâs View of Science and Organic Evolution
Kuhn then takes his argument even further. Having now essentially denied every popular basis for justification in belief the growth and progress of scientific knowledge, he then proposes (not unlike Popper before him) that science is actually very much like organic evolution. But, unlike Popper, Kuhn latches on to the non-teleological (i.e. non-purposeful) nature of evolution as his main thesis.
For many men the abolition of the teleological kind of evolution was the most significant and least palatable of Darwin’s suggestions. The Origin of the Species recognized no goal set either by God or nature. Instead, natural selection, operating in the given environment and with the actual organisms presently at hand, was responsible for the gradual but stead emergence of more elaborate, further articulated, and vast more specialized organisms.
What could ‘evolution,’ development,’ and ‘progress’ mean in the absence of a specified goal? To many people, such terms suddenly seemed self-contradictory. (The Structure of Scientific Revolutions, p. 172)
Kuhn therefore suggests that scientific progress is a non-teleological process, just like organic evolution. That is to say, the growth of scientific knowledge (which Kuhn does believe in) is not a growth towards some underlying reality, but merely a growth of solved problems that we humans found interesting.
This, then, is the primary difference between Kuhn and Popper â and itâs a huge difference in my opinion: Kuhn is a Positivist and Popper is a Scientific Realist. Popper believes that there is an underlying reality that we can grow closer to whereas Kuhn does not believe this is necessary to explain scientific progress.
 Supporting Kuhnâs views are luminaries such as Stephen Hawking, who recently wrote a book called The Grand Design that in part challenges the Scientific Realistâs view of science as well as (though he denies it) challenging the existence of God or at least the need for God in a scientific world view. I originally meant to include Hawkingâs thoughts within this post, but eventually realized it was too long. So Iâm going to briefly cover Hawkingâs defense of Positivism in a future post since I think his view is worthy of consideration even though I reject it.
 I have noted elsewhere that this view of Kuhnâs isnât entirely correct either. While is it true that there are many historical examples of scientific revolutions that failed to bring in older adherents to past paradigms, we also have the example of the standard model that quickly and easily converted all scientists despite the messiness of itâs model. Yet, Kuhnâs point is still often valid and that is enough for this discussion.
 Kuhn argues: âTo be accepted as a paradigm, a theory must seem better than its competitors, but it need not, and in fact never does, explain all the facts with which it can be confronted.â (The Structure of Scientific Revolutions, p. 18-19)
Then even more strongly:
The same point can be made at least equally effectively in reverse: there is no such thing as research without counterinstances. For what is it that differentiates normal science from science in a crisis state? Not, surely, that the former confronts no counterinstances. On the contrary, what we previously called the puzzles that constitute normal science exist only because no paradigm that provides a basis for scientific research ever completely resolves all its problems. The very few that have ever seemed to do so (e.g. geometric optics) have shortly ceased to yield research problems at all and have instead become tools for engineering. (The Structure of Scientific Revolutions, p. 79)
 Kuhn says: âNo part of the aim of normal science is to call forth new sorts of phenomena; indeed those that will not fit the box are often not seen at all.â (The Structure of Scientific Revolutions, p. 24)
Kuhn points to a not-so-well-known psychology experiment that is noteworthy. In this experiment, subjects are shown playing cards and are then asked to tell which suites they just saw. Unbeknownst to the subjects, the playing cards had been modified to contain non-existent suites, such as âa red six of spades and a black four of hearts.â Because the subjects had expectations built around a paradigm of what cards do and donât exist, initially none of the subjects could even see the anomalous suites. With complete confidence. âThe black four of hearts might, for example, be identified as the four of either spades or hearts.â Eventually, with increased exposure, some of the subjects started to see the anomalous suites. But some of the subjects not only never did, but started to not be able to tell what normal suites looked like any more. (The Structure of Scientific Revolutions, p. 63) Kuhn goes on to give numerous examples of how scientific theories form paradigms in which our expectations are built. Scientific theories therefore dictate not only what experiments are to be performed, but also how scientists will interpret the observational data.