So Kuhn is first making some claims about how science actually operates, and then drawing philosophical conclusions from those claims. Even if we leave aside the details of Kuhns claims, this strategy of argument was controversial and influential. Kuhn addressed philosophical questions about reason and evidence via an examination of history. As we saw in chapter z, the logical empiricists made a sharp distinction between questions about the history and psychology of science, on the one hand, and questions about evidence and justification, on the other. Kuhn was deliberately mixing together things that the logical empiricists had insisted should be kept apart. One of the reasons that Kuhn was interpreted as a "destroyer" of logical empiricism was that Kuhns work seemed to show how interesting it is to connect philosophical questions about science with questions about the history of science. Kuhn seemed to open up an exciting new way of approaching a set of problems that the logical empiricists were approaching in a very abstract manner. And although I emphasized in earlier chapters some appealing parts of the logical empiricist approach, I agree with Kuhn about the useful role of history in addressing philosophical questions about science.
Before we go deeper into the details of Kuhn's view, there is one other preliminary point to make. This has to do with a question that one should always ask when thinking about Kuhns theory and other theories like it. The question is, Which parts of the theory are just descriptive, and which are normative? That is, when is Kuhn just making a claim about how things are, and when is he making a value judgment, saying how they should be? Kuhn certainly accepted that he was making some normative claims (1996, 8). Some commentators were critical of Kuhn, however, because it's often hard to tell when he is just "saying how things are" and when he is making claims about good and bad science. My own interpretation of Kuhn stresses the normative element in his work. I think Kuhn had a very definite picture of how science should work and of what can cause harm to science. In fact, it is here that we find what I regard as the most fascinating feature of The Structure of Scientific Revolutions. This is the relationship between
i. Kuhns constant emphasis on the arbitrary, personal nature of factors often influencing scientific decisions, the rigidity of scientific indoctrination of students, the "conceptual boxes" that nature gets forced into by scientists .... and
z. Kuhn's suggestion that these features are actually the key to science's successwithout them, there is no way for scientific research to proceed as effectively as it does.
Kuhn is saying that without the factors referred to in (z), we would not have the most valuable and impressive features of science. But how can this be? How can features that look like failings and flaws actually help science? How can it help science for decisions to be made on the basis of anything other than what the data say? To answer these questions, we need to look more closely at the details of Kuhns story about scientific change.
5.3 Normal Science
Normal science is work inspired by a striking achievement that provides a basis for further work (a paradigm in the narrow sense). Kuhn does not think that all science needs a paradigm. Each scientific field starts out in a state of "preparadigm science." During this preparadigm state, scientific work can go on, but it is not well organized and usually not very effective. At some point, however, some striking piece of work appears. This achievement is taken to provide insight into the workings of some part of the world, and it supplies a model for further investigation. This achievement is so impressive that a tradition of further work starts to grow up around it. The field has its first paradigm.
What are some examples of paradigms? Kuhn gave examples from physics and chemistry, such as Newton's and Einstein's paradigms. Here I will mention two cases from other fields. Within psychology around the middle of the twentieth century, a great deal of work was based upon the behaviorist approach of B. F. Skinner. Two basic principles of Skinnerian behaviorism are (z) that learning is basically the same in humans, rats, pigeons, and other animals and (z) that learning proceeds by reinforcement-behaviors followed by good consequences tend to be repeated, while behaviors followed by bad consequences tend not to be repeated. Along with these principles, the Skinnerian paradigm included a set of experimental tools, such as standardized boxes in which pigeons made choices in response to stimuli by pecking lighted keys. It also included statistical techniques used to analyze data and various habits and skills for working out relevant and interesting experiments.
Here is an example from biology. Modern molecular genetics is based on a set of principles such as the following: (z) genes are made of DNA (in all organisms except some viruses, which have RNA genes), (z) genes have their effects by producing protein molecules and regulating other genes, and (3) nucleic acids (DNA and RNA) specify the structure of proteins but not vice versa. This last principle is often called "the central dogma." Along with these theoretical claims, molecular genetics includes a set of techniques for sequencing genes, for producing and studying mutations, for analyzing the similarity of different genes, and so on.
For Kuhn, a scientific field usually has only one paradigm guiding it at any particular time. Sometimes Kuhn wrote as if this were true by definition-a field being defined as an area of scientific investigation unified by a single paradigm. This led him to divide some scientific fields up more finely than is usual. Kuhn does allow that occasionally a field can be governed by several related paradigms, but this is rare. In general, a key part of Kuhn's theory is the principle one paradigm per field per time.
A paradigm's role is to organize scientific work; the paradigm coordinates the work of individuals into an efficient collective enterprise. A key feature that distinguishes normal science from other kinds of science for Kuhn is the absence of debate about fundamentals. Because scientists doing normal science agree on these fundamentals, they do not waste their time arguing about the most basic issues that arise in their field. Once biologists agree that genes are made of DNA, they can focus and coordinate their work on how specific genes affect the characteristics of plants and animals. Once chemists agree that understanding chemical bonding is understanding the interactions between the outer layers of electrons within different atoms, they can work together to investigate when and how particular reactions will occur. Kuhn places great emphasis on this "consensus-forging" role of paradigms. He argues that without it, there is no chance for scientists to achieve a really detailed and deep understanding of phenomena. Detailed work and revealing discoveries require cooperation and consensus. Cooperation and consensus require closing off debate about fundamentals.
As usual, we should be careful to distinguish between the descriptive and the normative here. Kuhn certainly claims that normal science does close off debate about fundamentals. But does he go beyond that and claim this is something that normal science should do? I think it is clear that he does (see Kuhn 1996, 24-25, 65), but these issues are controversial.
If Kuhn does make a normative claim here, then we see an important contrast with Popper. Although Popper can certainly allow that not everything can be criticized at once within science, Popper's view does hold that a good scientist is permanently open-minded with respect to all issues in the field in which he or she is working, even the very basic issues. Any "closing off" of debate is bad news according to Popper. Popper criticized Kuhn explicitly on this point; Popper said that although "normal science" of Kuhns kind does occur, it is a bad thing that it does (1970).
What is the work of a good normal scientist like? Kuhn describes much of the work done in normal science as "puzzle-solving." The normal scientist tries to use the tools and concepts provided by the paradigm to describe, model, or create new phenomena. The "puzzle" is trying to get a new case to fit smoothly into the framework provided by the paradigm. Kuhn used the term "puzzle" rather than "problem" for a reason. A puzzle is something we have not yet solved but which we think does have a solution. A problem might, for all we know, have no solution. Normal science tries to apply the concepts provided by a p
aradigm to issues that the paradigm suggests should be soluble. Part of the guidance provided by a paradigm is guiding the selection of good puzzles.
The term "puzzle" also seems to suggest that the work is in some way insignificant or trivial. Here again, Kuhn intends to convey a precise message with the term. A normal scientist does, Kuhn thinks, spend a lot of time on topics that look insignificant from the outside. (He even uses the term "minuscule" [1996, 241.) But it is this close attention to detail-which only the well-organized machine of normal science makes possible-that is able to reveal deep new facts about the world. I think Kuhn felt a kind of awe at the ability of normal science to home in on topics and phenomena that look insignificant from outside but which turn out eventually to have huge importance. And although the normal scientist is not trying to find phenomena that lead to paradigm change-far from it!-these detailed discoveries often contain the seeds of large-scale change and the destruction of the paradigm that produced them.
5.4 Anomaly and Crisis
I said that a central feature of normal science, for Kuhn, is that the fundamental ideas associated with a paradigm are not debated. Fundamental principles are insulated from refutation. Normal scientists spend their time trying to extend the paradigm, theoretically and experimentally, to deal with new cases. When there is a failure to get the results expected, the good normal scientist reacts by trying to work out what mistake she or he has made. The proverb "only a poor workman blames his tools" applies. The normal scientist should take failure as a challenge.
Kuhn accepts that theories are sometimes refuted by observation; within normal science, hypotheses are refuted (and confirmed) all the time. The paradigm supplies principles for making these decisions. But throwing out an entire paradigm is much more difficult. According to Kuhn, the rejection of a paradigm happens only when (z) a critical mass of anomalies has arisen and (z) a rival paradigm has appeared. For now we will look just at the first of these-the accumulation of a critical mass of anomalies.
An "anomaly" for Kuhn is a puzzle that has resisted solution. Kuhn holds that all paradigms face some anomalies at any given time. As long as there are not too many of them, normal science proceeds as usual and scientists regard them as a challenge. But the anomalies tend to accumulate. Sometimes a single one becomes particularly prominent, by resisting the efforts of the best workers in the field. Eventually, according to Kuhn, the scientists start to lose faith in their paradigm. The result is a crisis.
Crisis science, for Kuhn, is a special period when an existing paradigm has lost the ability to inspire and guide scientists, but when no new paradigm has emerged to get the field back on track. The transition to a crisis is almost like a phase transition, like the change of a substance from solid to liquid during melting. For whatever reason, the scientists in a field lose their confidence in the paradigm. As a consequence, the most fundamental issues are back on the table for debate. Amusingly, Kuhn even suggests that during crises scientists tend to suddenly become interested in philosophy, a field that he sees as quite useless for normal science.
I used the term "critical mass" of anomalies to describe the trigger for a crisis. This atomic-age metaphor is appropriate in several ways. In particular, I use it here to suggest that Kuhn sees the breakdown of a paradigm as something that is part of the "proper functioning" of science, though it does not feel that way to the scientists involved. Normal science is structured in a way that makes its own destruction inevitable, but only in response to the right stimulus. The "right stimulus" is the appearance of problems that are deep rather than superficial, problems that reveal a real inadequacy in the paradigm. Because normal scientists will tolerate a good deal of temporary trouble without abandoning normal science-they will blame the failure on themselves, at least for a while-a paradigm does not break down easily. But when the right stimulus comes, the paradigm will break down. In this way, a paradigm is like a well-shielded and well-designed bomb. A bomb is supposed to blow up; that is its function. But a bomb is not supposed to blow up at any old time; it's supposed to blow up in very specific circumstances. A well-designed bomb will be shielded from minor buffets. Only a very specific stimulus will trigger the explosion.
Some might find this militaristic analogy unpleasant, but I think it captures a lot of what Kuhn says. Kuhn's story is guided by his claim that all paradigms constantly encounter anomalies. For a Popperian view, or for other simpler forms of empiricism, these anomalies should count as "refutations" of the theory. But Kuhn thinks that science does not treat these constantly arising anomalies as refutations, and also that it should not. If scientists dropped their paradigms every time a problem arose, they would never get anything done.
Much of the secret of science, for Kuhn, is the remarkable balance it manages to strike between being too resistant to change in basic ideas, and not being resistant enough. If the simplest form of empiricist thinking prevailed, people would throw ideas away too quickly when unexpected observations appeared, and chaos would result. Ideas need some protection, or they can never be properly developed. But if science was completely unresponsive to empirical failures, conceptual advance would grind to a halt. For Kuhn, science seems to get the balance just right. And this delicate balance is not something we can describe in terms of a set of explicit rules. It exists implicitly in the social structures and transmitted traditions of scientific behavior, and in the quirks of the scientific mind.
These ideas about the balance that makes science work are an important challenge to empiricism, at least in its simpler forms. The idea that a willingness to revise ideas in response to observation can go too far is unexpected from the point of view of empiricist philosophy. And Kuhn supported this claim with a mass of evidence from the history of science.
So far we have gone from preparadigm science, through normal science, to crisis. The next stage in Kuhns story is revolution. But before we get there, I will make some summary remarks about Kuhns theory of normal science.
5.5 Wrap-up of Normal Science
Let's sum up what we have so far. Paradigms function to organize scientific work. Normal science is work aimed at extending and refining the paradigm. A good normal scientist is committed to the paradigm and does not question it. Normal scientists extend their paradigm both theoretically and experimentally. Anomalies inevitably arise, however, and eventually these reach a kind of critical mass, at which point scientists lose faith in the paradigm and the field plunges into a state of crisis.
We have not yet reached the most controversial part of Kuhn's theory, but are there any problems with what we have so far? One problem comes from Kuhn's insistence that, except in unusual cases, a scientific field has one paradigm per field per time. Kuhn held that, in general, a single paradigm will dominate its field. He did not think that two or three separate and competing paradigms could normally coexist. Many critics have thought Kuhn was wrong about this, both in the cases of physics and chemistry, which he discussed extensively, and, even more so, for areas like biology and psychology, which he did not often discuss. We will come back to this issue in chapter 7.
Secondly, Kuhn exaggerates the degree of commitment that a normal scientist does and should have to a paradigm. Kuhn describes the attitude of a normal scientist in very strong terms. Scientific education is a kind of "indoctrination;' which results in scientists having a deep "faith" in their paradigm. As a description of how science actually works, this seems exaggerated. Sometimes there is a faithlike commitment, but sometimes there is not. Many scientists are able to say that they always work within a paradigm, for practical reasons, while being very aware of the possibility of error and the eventual replacement of their framework. One of the ironies of Kuhn's influence is that his book might have weakened the faith of some normal scientists, even though Kuhn thought that normal scientists should have a deep faith in their paradigms!
Leaving aside the factual issue of whether a tenacious commitment to a paradigm is what we generally find, we should also ask about
Kuhns belief that this strong commitment is a good thing. For Kuhn, the great virtue of normal science is its organized, coordinated structure, a structure that results in precision and efficiency. Unless debate about fundamentals is closed off, this precision and efficiency will be reduced. A key contrast here is with Popper, who insists on permanent open-mindedness. For Kuhn, a constant questioning and criticism of basic beliefs is liable to result in chaos-in the partially "random" fact-gathering and speculation that we see in preparadigm science. But here again, Kuhn probably goes too far. He does not take seriously the possibility that scientists could agree to work together in a coordinated way, not wasting time on constant discussion of fundamental issues, while retaining a cautious attitude toward their paradigm. Surely this is possible.
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