VI. Reactions to Kuhn Noretta Koertge
Although Kuhn explicitly says that a philosophical theory of science should be elucidated by applying it to the history of science (S.S.R., p. 9) and although his writings are chock full of short allusions to historical episodes, there have been few explicit attempts either to write history of science from a Kuhnian perspective or to systematically test Kuhn's theory against detailed historical case studies. Nevertheless, there have emerged several general reservations about the adequacy of Kuhn/s model as an accurate description of either the past or present workings of science.
The most common criticism is that Kuhn exaggerates both the breadth and depth of consensus within science. For example, David Hull has argued that there were no theoretical principles that leading Darwinians agreed on (Hull, ). When one looks closely at any period of what one might expect to be normal, monoparadigmatic science, there always seems to emerge an amazing diversity of views and on a variety of levels: some phlogistonists believed in three earths, others in four; some post-Lavoisier chemists thought muriatic acid contained oxygen, others didn't; there were repeated debates about atomism from the middle of the 19th century until the energetics movement with Ostwald and Mach; there is a continuing history of debated amongst scientists over the interpretation of quantum mechanics; on a more mundane level quantum chemists have disagreed about the relative advantages of the "valance bond" versus "molecular orbital" computational approaches. And in the Postscript to the 2nd edition of his book, Kuhn admits that the size of the scientific community which share a paradigm may be fewer than twenty-five people and that the various restructurings of group commitments which takes place may not seem at all revolutionary to folks outside the small research group (p 181). Of course, once the existence of micro-paradigms and mini-revolutions is granted, the distinctions between pre-paradigm science, normal science, and crisis science become somewhat blurred and Kuhn's model seems less attractive as a framework for characterizing distinct developmental stages in various disciplines.
By far the most critical commentary on Kuhn's theory, however, has dealt not with its descriptive adequacy, but with the normative issues which it raises. In short, the question is not whether most scientific communities do in fact
operate according to Kuhn's model, but whether they should. This normative critique asks whether on Kuhn's account there is any objective sense in which a later paradigm is better than an earlier account. On his account does science really progress or does it just change? And if it does progress, are the mechanisms by which paradigm shifts occur rational ones? Can one give cogent arguments for the way scientists operate with paradigms or is their scientific behavior the result of blind social dynamics? I cannot begin to summarize in detail this multi-faceted debate here - in fact - the remainder of this book could be thought of as reactions to Kuhn - but we will look briefly at the key issues.
a. Scientific Progress
Outside the circle of Anglo-American philosophers of science, the claim that science has obviously progressed is viewed as tendentious or at best naive. For, the argument would go, it is not at all obvious that the negative effects of twentieth century science, such as the threat of nuclear weapons and the various chemicals which endanger our environment are outweighed by the positive contributions science has made in controlling disease and relieving drudgery. From this perspective the claim that there has been scientific progress is quite problematic and the idea that we want to encourage the growth of science conjures up pictures of an ever expanding army of white-coated Dr. Frankensteins in quest of the "technically sweet."
However, when philosophers wonder if, on Kuhn's account, science progresses, what they have in mind is cognitive progress and here the assumption is that science clearly makes a dramatic kind of cognitive progress which any respectable philosophical account should describe. Even if we limit our appraisal to the cognitive aspects of science, it could still be disputed whether later cognitive schema are clearly superior, especially if we consider lost technical skills, such as making Stradavarius violins and the rapidly disappearing expertise of various native peoples. However, all that is assumed here is that there is overall progress, not that every single step is progressive nor that there are not also losses.
I have deliberately left the phrase 'cognitive progress' quite vague, for each philosophy of science analyzes it somewhat differently. Let us review a couple of definitions of progress and then see why there are concerns about whether Kuhn's account attributes progress to science.
In almost all contexts, progress has the connotation of moving towards a desirable goal or in a favorable direction. So if science makes cognitive progress, later scientific systems should be cognitively superior to earlier ones.
According to the positivists, science, if properly conducted, would yield more and more true, justified beliefs. The scientific process would produce a more or less continuous accumulation of information about the world which hopefully could be codified in a more and more unified structure. In short, the layer cake should expand in both the horizontal and vertical dimensions.
For the early Popper, the attribution of progress to science was a little more problematic. If the history of science is viewed simply as a string of falsified conjectures with only the very latest one as yet unrefuted, it is difficult to see how we have progressed, at least on the theoretical level. Of course, our stock of 'basic' statements will have expanded, so there are an increasing number of constraints on any new conjectures - so in a sense our problems are getting progressively more difficult.
The need to have a fuller notion of progress was one of Popper's main motivations for the introduction his theory of verisimilitude. If we look at the Aristotelian, Galilean, and Newtonian account of falling bodies from a post-Einsteinian perspective, we see that all are strictly speaking false, yet intuitively there is clearly an increase in verisimilitude because Newton's account (which takes account of the varying strength of the gravitational field) is a better approximation than Galileo's than Aristotle's (which is only semi-quantitative). As we saw earlier, there are problems making the notion of verisimilitude more precise and in measuring it, but Popper's informal notion certainly captures a lot of what we have in mind when we talk about scientific progress - scientists seem to be trying to weed out the false parts of our conceptual scheme while increasing the number of true components.
When we turn to Kuhn's theory of the development of science it is easy to see how one could describe the periods of normal science as progressive. Scientists are successful in extending the primary theories of the paradigm to cover new phenomena, more accurate instruments are designed, and some of the puzzles set by the paradigm are solved. Normal science seems to generate theoretical, empirical and technological progress.
But it is less clear whether we would be justified in claiming there is progress during scientific revolutions. It would seem from his informed commentary that Kuhn himself believes that the switch to the Newtonian paradigm, say, was a progressive one, but on his philosophical account of the nature of revolutions it is difficult to see exactly how the paradigms could be compared because they are, as Kuhn says, incommensurable. We will discuss exactly what he might mean by this in the next section. But the general problem is this: To speak of progress implies that there are one or more scales or dimensions on which we can rank order items. But in the case of paradigm change it's difficult to think what candidates for the scale might be. Progress can't be an increase of observation statements because these will be quite different in successive paradigms. Even when the words remain invariant, as in "The sun rises in the East", there will typically be a dramatic change of meaning, for example, in the way "rise" is interpreted or in the important properties ascribed to the sun.
It is not even possible to speak unambiguously about improvements in measuring instruments as we move from one paradigm to another. Strictly speaking, on Kuhn's account the barometer was developed to measure the "force of the vacuum", not atmospheric pressure, and the original calorimeter measured the amount of the element caloric which was released, not a quantity related to the average motion of molecules. So even when a bit of pre-revolutionary apparatus remains in the post-revolutionary laboratory, Kuhn would say that it is used to measure different things! Of course, some devices may get thrown out completely, such as craniometers and leeches. Others, such as Rohrschach tests and alchemical retorts, fall out of favor and are relegated to the attic, not because there is a new, better device which serves exactly the same function, but because in the light of the new paradigm the task is no longer considered to be important.
Kuhn says that scientists prefer the new paradigm because they believe it has more problem-solving power than the old one which was known to be besieged with anomalies. But he also emphasizes that, strictly speaking, new paradigms never solve the problems set by their predecessors because the problems themselves, as well as the proffered solutions, are paradigm dependent. Textbooks may say that the problem of projectile motion was always an anomaly for Aristotelians whereas Galileo solved it. But if we look carefully, Galileo didn't actually solve Aristotle's problem - he reformulated it. For Aristotle, the major puzzle was how a projectile could keep moving without a mover once it was launched. In Galileo's inertial theory, this problem is obviated.
Kuhn also emphasizes the explanatory losses which accompany paradigm shifts. For example, the Aristotelian paradigm tried to give a unified account of the growth of plants, the motions of falling bodies, and the goal-directed activities of human beings. Later paradigms repudiated teleological explanations, but it could be argued that there is nevertheless a kind of loss; as the current interest in the so-called Anthropic Principle illustrates, people still find such modes of explanation very attractive.
Loss on a less grand scale is illustrated by Kuhn's example of the switch from phlogiston theory to oxygen theory which involved a loss of attempts to relate the color changes which occurred during chemical reactions to a change in the state of phlogistication.
My conclusion so far is this: If Kuhn's account of scientific revolutions were correct, then it becomes very difficult to describe any sense in which the new paradigm is objectively better than the old one. (Of course, scientists feel it is better or they wouldn't switch.) Thus if one judges later paradigms, such as Keplerian astronomy, to constitute genuine progress over earlier ones, such as Ptolemaic astronomy, then one must reject Kuhn's detailed account of the nature of paradigms and/or scientific revolutions. In the next section we will report some of the aspects of Kuhn's account which philosophers think are wrong and which prevent him from accounting for objective progress in science.
b. Incommensurability
Kuhn's most famous and controversial claim is that the process of paradigm change is like a Gestalt switch or religious conversion. Although dissatisfactions with the old paradigm may accumulate over a long period of time and one may articulate them in a fairly rational manner, the change itself occurs rapidly, irreversibly, and arationally. One cannot be argued into switching paradigms any more than one can be argued into seeing the rabbit as a duck. Of course, once the transition has occurred, scientists in the new paradigm loudly proclaim its 'objective' virtues and denounce their former colleagues as irrational old fogies.
Kuhn's account of paradigm transition fits in very well with his characterization of normal science. Because the different aspects of a good paradigm are so well-integrated (instruments and observations are interpreted via the paradigm's theory and regulated by its methodology; the preferred methodology depends on ontology, which in turns interacts with theory), it becomes almost impossible to make piecemeal evaluations of the paradigm -it stands or falls as a whole. Critical analysis is made even more difficult by the fact that much of the cognitive content of the paradigm is tacit. For example, the problem-solving and interpretive skills which scientists have learned by working with exemplary cannot be articulated. The positivist Neurath wrote of how difficult it is to rebuild a ship while at sea. On Kuhn's account the planks of the ship are so invisible and so welded
together that it is impossible to repair it - one simply jumps on to some quite different boat.
Probably all of us have experienced something like the clash between incommensurable systems which Kuhn describes - cases where rational argument seems ineffective and the only ways which seem open to a resolution of the conflict is to either banish our bloody-minded opponents or else try to convert them through threats, bribes, or rhetorical persuasion. (The examples which spring to my mind include not only big international ideological conflicts but also academic debates over the merits of Women's Studies Programs, inter-disciplinary discussions on any topic, and conversations between teenagers and their parents about music, clothes and etiquette!) So let us grant for the moment that phenomena reminiscent of Kuhnian incommensurability are widespread. But does it play a major role in scientific revolutions? I will proceed by looking at various aspects of the incommensurability claim. How exactly is it that communications between holders of two rival scientific paradigms is supposed to be impeded?
First, let us dispose of one rather crude mistake which I will call pseudo-conceptual incommensurability. It is sometimes claimed that Aristotle had no concept of inertia or of motion in a vacuum, while Newtonians did, the implication being that since the systems employ different concepts they cannot be compared. It is true that Aristotle didn't believe that there could be motion without a mover nor motion except in a plenum because he said so! So in some crude ordinary language sense he didn't "have" the modern concepts, but since he explicitly brought up these possibilities only to refute them, he could have understood immediately what the moderns were claiming about these topics, although he might not have immediately grasped why they were making these claims. Conversely, the moderns knew full well that they were directly contradicting Aristotle on these points - they were not just inviting Aristotelians to forget about ducks and change to rabbits. There is a big difference between lacking the linguistic capabilities to discuss an idea and failing to believe that the world instantiates the idea.
Having described this basic mistake as a crude one, let me now admit there can be confusing cases! First of all, although Aristotle had a single word for void (since the atomists had discussed it), there was no simple expression for inertia. So although Aristotle explicitly denied the possibility of what we call inertial motion, it is true that he would have had to learn a new term in order to discuss this idea using Newtonians terminology. In this case it seems obvious that Aristotle had the linguistic resources to easily do so. However, whenever one is dealing with non-formalized natural languages we could imagine cases arising where it is unclear exactly what the capacity of the pre-revolutionary language is. And there could in principle be cases where a new concept, though technically expressible in the old language, could only become psychological accessible through prolonged training. (Imagine trying to plunge into a late chapter in the Principia Mathematica equipped only with the axioms and a string of definitions.)
Let us now turn to a case of genuine conceptual incommen-surability, a situation in which it is impossible to define
a concept from one scientific theory (S) using the terminology of a second scientific theory (T). To illustrate, consider a mathematical example. According to Euclidean geometry it is logically impossible to have a triangle whole angles don't add up to 180_. Hence, it is not possible even to ask from within Euclidean geometry about the properties of Riemannian triangles. Unlike the Aristotle examples above, the claim is not that Riemannian triangles don't exist; rather the situation is that they are unspeakable!
A scientific example arose in connection with the word element. If by element we mean the last product of analysis, then how can we talk to someone who claims to have separated the element hydrogen into deuterium and light hydrogen?
So there indeed appear to be cases of genuine conceptual incommensurability, cases where concepts within competing theories S and T are not intertranslatable. Does this mean, however, that it is impossible for scientists to make a reasoned comparison between S and T? Not at all. Let us see why.
Thanks to the logical positivists when philosophers speak of the language of a science, say the language of Newtonian mechanics, we tend to think primarily of the axioms of the core theory plus perhaps descriptions of measuring instruments. However, there is no way Newtonian scientists can develop Newtonian science without a rich philosophical meta-language. Scientists (not just philosophers) need to talk about whether Newton's first law is a tautology, to clarify what is meant by action at a distance, to discuss the status of the infinitesimals used in Newton's formulation of the calculus, the domains in which the law of universal gravitation has been tested, etc. The same sort of meta-language needed for the conduct of normal science can also be used for the comparison of two theories which are not inter-
translatable. In the meta-language one can then discuss which geometry is most useful for surveying or which theory of elements better represents chemical phenomena.
So conceptual incommensurability does not preclude the rational comparison of theories. Of course, this debate conducted within the meta-language can only take place in a sensible fashion if both parties understand both of the conceptually incommensurable theories, and there could be cases where this task of dual comprehension is psychologically difficult. But what if the holders of the two rival paradigms hold different cognitive values? If their standards and methods of appraising scientific systems do not agree, then we are indeed left with an irresolvable form of incommensurability. We will discuss the extent to which scientists really have deep disagreements about what constitutes good science later in our chapter on Laudan. But suffice it so say for now that there seems to be much less dispute about the desiderata for a good scientific theory than there is about what constitutes good art, good literature, good history, or good theology. More often, I think, scientists are disagreeing about their guesses as to which direction of research is more likely to produce the kind of theory which all agree would be desirable. In our chapter on Lakatos, we will look in more detail at the problem of giving an objective appraisal of the heuristic power of a research program.
So far we have looked at various sources of incommensurability and concluded that they need not lead to a breakdown of rational debate. (Laudan even argues that value conflicts can be resolved.) But we have also admitted that it may not be easy to get clear about exactly what the rival theories are saying and what the relative strengths and weaknesses of their claims are. Let us now look at some of the sources of what we might call psychological incommensurability. If the task of rational theory comparison, though logically possible, turned out to be too psychologically demanding, then we would have to concede Kuhn some aspects of his account of non-rational paradigm change.
Kuhn places a lot of emphasis on the tacit (inarticulated) content of a paradigm, stressing the role of concrete exemplars which serve both as an embodiment of theory and as a heuristic guide for the application of rather abstract theoretical claims to new situations. If crucial aspects of a theoretical approach cannot be written down but reside only in the "know-how" of a practitioner, then paradigm comparison becomes rather like trying on shoes or choosing a violin - one may talk a lot about width of the last or sweetness of sound (and indeed there are clear cases of bad fitting shoes and inferior violins) - but in the last resort it seems to be a matter of what "feels" right. The subtle, yet crucial differences are indescribable. Furthermore, once we get accustomed to our Birkenstocks or Stradivarius, it becomes increasingly difficult to even imagine that anything could be better and so we have a tremendous psychological resistance even to trying on any alternative.
Current work in cognitive science is now giving us some insight into how Kuhn's concrete exemplars might work. For example, according to prototype theory, the structure of a concept, say bird, contains not only universal characteristics, such as is an animal, but also prototypical instances, such as robin. From the prototypes we extract default rules, such as "if it's a bird, [assume] it eats bugs and flies [unless you have explicit information to the contrary]."
Thus we can imagine a situation where two parties agree on the defining characteristics of birds and on all the universal generalizations regarding birds, but yet have very different bird prototypes and hence different default rules. (If my prototypical bird is a penguin, my hunches, identification errors, the analogies to birds which I generate, etc. will be quite different from the person whose Ur-bird is a flamingo!)
Now with effort, we can probably learn to articulate these prototypes (my guess is that good real estate agents have the knack of figuring out what each client's prototypical house is like). But unless we do so, we are apt to end up in strange-sounding conversations about whether an Irish Wolfhound is "really" a dog, or the earth "really" a planet. What is being disputed in such cases is not what technically falls under the concept of dog or planet, but the choice of prototypes.
Undoubtedly similar conflicts occur in science. For Galileo, prototypical free fall took place in a vacuum; for Aristotle bodies fell through a medium. For Plato, the prototypical motion of a celestial body was a circle; for Newton, it was a conic section with some other mass at the focus. For Mendel, the prototypical inheritance pattern let to assortment; others posited blending.
Disagreements over prototypes are difficult to articulate and very hard to arbitrate, partly because we need not be committed to saying that our prototype is in fact statistically most common! But by the same token, if all the dispute amounts to is a disagreement about prototypes, then little hinges on it.
Even Kuhn admits that the tacit components of a paradigm tend to be made more explicit during times of crisis. And of course that is just when we need to have them articulated for purposes of rational choice between paradigms.