Are discourse communities incommensurable in a fragmented psychology? The possibility of disciplinary coherence.

The question of incommensurability is an overlooked issue that has profound consequences for our ability to understand relationships and utilize common standards for comparison, contrast, and evaluation in psychology. Are the differences among discourse communities so deep that there is no common commensurate no common measuring stick for making comparisons among communities? If so, then the community of communities, the discipline of psychology, has no way to compare competing knowledge claims, and no way to effect disciplinary unity and coherence. Kuhn s distinction between incommensurability and incompatibility is described, along with its challenge to Enlightenment rationality and scientific method for brokering the relativity among discourse communities. Popper s misconception that this challenge implies an anything goes nihilism is also discussed, specifically his misconception that incompatibility and incommensurability mean incomparability. On the contrary, the article shows how recognizing the incommensurable is often the key to comparison, and thus disciplinary coherence and unity. Are Discourse Communities Incommensurable in a Fragmented Psychology? The Possibility of Disciplinary Coherence As Yanchar (this issue) has described, the authors of this special journal issue believe there are three main questions that need to be answered before the issue of psychology s fragmentation can be adequately addressed (see alsoYanchar and Slife, 1997). Clearly the first, from our perspective, is the question of incommensurabilty, the question of how deep the differences among the various communities of psychology go. Are these differences so deep that there is no common commensurate -no common measuring stick -for making comparisons among these communities? Are they so deep that the only valid comparisons are those within a community and not across communities? If so, then the community of these communities -the discipline of psychology -has no way to compare competing knowledge claims across communities, no way to evaluate who is most correct or most effective, especially when such claims directly oppose one another. In this sense, the question of incommensurability is the most fundamental question of the fragmentation issue. All questions of coherence, correspondence, unification, and, indeed, relationships in general hang in the balance, because these questions all depend on some modicum of common standards in which to compare the divergent communities. Of course, the ability to form valid comparisons is not just important to disciplinary fragmentation but to any topic or field that attempts to understand differences and similarities among divergent communities -present or past, animate or inanimate. Thus, the incommensurability question is vital not only to the philosophy of science (the broader grounding of this special issue) but also to historicism, constructionism, relational therapies, objectivism, multiculturalism, and ethics, to name but a few. Indeed, as Richard Rorty (1979, p. 316) points out, the notion that all discourse communities are ultimately commensurable is the fundamental bias of epistemology since Descartes bias, incidentally, that Rorty seeks to eliminate. This bias, however, is not typically made explicit, nor are its implications generally understood in psychology. Part of the task in this article, then, is not only to show why this question is significant, but also to explicate what the term incommensurability means, both in definition and in significance. As we shall see, the answer to the question posed in the title will be the more familiar academic answer to many questions: "yes and no, it depends." However, the whole notion of "it depends" depends itself upon the whole notion of incommensurability, as this article will show. Setting the Stage The question of incommensurability is so rarely raised in psychology that a brief background on the topic might be helpful. The incommensurability issue originally arose most explicitly in the philosophy of science. Thomas Kuhn (1970), in his well-read and well-slandered book, The Structure of Scientific Revolutions, is perhaps the most responsible for first giving the question visibility. His initial foray into the question was later followed up by his philosophical colleagues: Feyerabend, Lakatos, Popper, and Toulmin. Kuhn's primary contention was that the model for how a scientist chooses theories must be changed from the "received view." Kuhn (1970) was skeptical about the search for "an algorithm able to dictate rational unanimous choice" and emphasized, instead, that the criteria of choice "function not as rules, which determine choice, but as values, which influence it" (emphasis added, p. 331). This notion that science is value-laden was somewhat controversial at the time, but Kuhn's contention that these values could themselves be incommensurable touched off a firestorm of debate in philosophy of science circles. No less than the enfant terrible of philosophy, Paul Feyerabend (1975), essentially supported Kuhn's position, while Karl Popper (1972) perhaps the most famous philosopher of science of our time lined up against Kuhn. What was this heated debate all about? It is important, particularly, that we understand what Kuhn was contending, because as Richard Bernstein (1983) and others have noted, Kuhn has been mightily mischaracterized and misunderstood in the process of this polemic. As most undergraduate psychology majors can tell you, Kuhn basically railed against the linear notion of scientific progress. He held, as the title of his book indicates, that science develops through incommensurable revolutions. As he put it, "the tradition that emerges from a scientific revolution is not only incompatible but often actually incommensurable with that which has gone before" (Kuhn, 1970, p. 103). As this quote makes clear, incommensurability is not the mere incompatibility of theories. The concept of incompatibility is a logical one. Two theories are logically incompatible if they entail a logical contradiction, which may seem in our era of PostEnlightenment rationality about the worst sort of difference imaginable. However, such a position assumes that there is some sort of objective commensurate -whether it be logic, method, or rationality itself -from which to make the comparison. When Kuhn and Feyerabend held that revolutionary theories are not only incompatible but also incommensurable, they were contending that no such objective rationality exists. That is, they were holding that even the logic and rationality of the two theories may differ. Kuhn (1970) made this point most clearly when he likened the competing paradigms to "different worlds" (p. 150). Indeed, as Kuhn considered it, this aspect of incommensurability is the "most fundamental aspect" of competing paradigms (p. 150). A lengthy quote will illustrate this aspect of Kuhn's notion of incommensurability best: In a sense that I am unable to explicate further, the proponents of competing paradigms practice their trades in different worlds. . . . Practicing in different worlds, the two groups of scientists see different things when they look from the same point in the same direction. . . .[That is why], before they can hope to communicate fully, one group or the other must experience the conversion that we have been calling a paradigm shift. Just because it is a transition between incommensurables, the transition between competing paradigms cannot be made a step at a time, forced by logic and neutral experience. (p. 150) Feyerabend (1975, 1977) made a similar contention in his distinction between three types of incommensurability. He goes on to claim that there is really only one type which is meant by Kuhn and others when using the term. This type of incommensurability assumes that different paradigms "use concepts that cannot be brought into the usual logical relations of inclusion, exclusion, overlap" (Feyerabend, 1977, p. 363). In this sense, it is clear that Kuhn and Feyerabend are going well beyond the mere incompatibility of theories. It is clear they are claiming that the received view of rationality is not up to the challenge of comparing rival paradigms, because the received view of rationality is itself part of one paradigm. The Controversy Enter Karl Popper onto our philosophy of science stage. Popper saw the claims of Kuhn and Feyerabend as an unmitigated attack on the rationality of science. If science cannot justify its choice of theories on rational grounds, then it is essentially groundless and relativistic. Popper (1970) used the metaphor that he has called the "Myth of the Framework" to illustrate this groundlessness (p. 56). This metaphor depicts scientists as "prisoners caught in the framework of our theories" (p. 56). These prisoners are so locked into their individual communal frameworks that persons from outside their community cannot communicate with them. They lack a common grounding, including a common language, and even a common method for accurately translating languages. Popper, of course, considered this to be a dangerous myth. He feared that if it was believed and upheld, it would lead science ultimately to relativism and nihilism. It is Popper's critique of Kuhn and Feyerabend, and the agreement of so many psychologists with that critique (e.g., Capaldi & Proctor, 1999), that provides the impetus for the present article. If psychology is fragmented into communities that are similar to paradigms and as Yanchar and Slife (1997) have noted, there is certainly evidence that it is then the Kuhn/Popper question has to be answered before we can proceed to address the issue of psychology's fragmentation. That is, can the various paradigms of psychology communicate with one another? Are the many discourse communities of psychology prisoners of their theories and assumptions about the world, as Popper warned? Are they truly in different worlds, in t