Xiang Chen

Many recent cognitive studies reveal that human cognition is inherently perceptual, sharing systems with perception at both the conceptual and the neural levels. This paper introduces Barsalou's theory of perceptual symbols and explores its implications for philosophy of science. If perceptual symbols lie in the heart of conceptual processing, the process of attribute selection during concept representation, which is critical for defining similarity and thus for comparing taxonomies, can no longer be determined solely by background beliefs. The analogous nature of perceptual symbols and the spatial nature of intraconceptual relations impose new constraints on attribute selection. These constraints help people with different background beliefs select compatible attributes, which constitute a common "platform" for taxonomy comparison.

In a previous article we have shown that Kuhn's theory of concepts is independently supported by recent research in cognitive psychology. In this paper we propose a cognitive re-reading of Kuhn's cyclical model of scientific revolutions: all of the important features of the model may now be seen as consequences of a more fundamental account of the nature of concepts and their dynamics. We begin by examining incommensurability, the central theme of Kuhn's theory of scientific revolutions, according to two different cognitive models of concept representation. We provide new support for Kuhn 's mature views that incommensurability can be caused by changes in only a few concepts, that even incommensurable conceptual systems can be rationally compared, and that scientific change of the most radical sort—the type labeled revolutionary in earlier studies—does not have to occur holistically and abruptly, but can be achieved by a historically more plausible accumulation of smaller changes. We go on to suggest that the parallel accounts of concepts found in Kuhn and in cognitive science lead to a new understanding of the nature of normal science, of the transition from normal science to crisis, and of scientific revolutions. The same account enables us to understand how scientific communities split to create groups supporting new paradigms, and to resolve various outstanding problems. In particular, we can identify the kind of change needed to create a revolution rather precisely. This new analysis also suggests reasons for the unidirectionality of scientific change.

Kuhn regards local incommensurability as an unavoidable result of changes in worldview, but his account fails to explain both historical cases in which rivals with different paradigms obtained consensus, and psychological experiments in which people with different cultural backgrounds accurately presented other points of view. Although the conditions required to generate local incommensurability were present in the dispute between Brewster and Herschel on light absorption, they succeeded in communicating. Ultimately Brewster understood his opponent's position, in the same way that subjects in Barsalou's recent psychological experiments proved able to comprehend alien conceptual structures. Building upon recent cognitive theories of graded conceptual structures, I offer a new account of incommensurability, which accommodates these historical cases and psychological results. By correcting and extending Kuhn's account I show that local incommensurability may be a matter of degree.

Previous studies of the history of optics reveal that the confrontation between the emission theory of light and the undulatory theory of light in Britain occupied a considerable period during the early nineteenth century. After the majority of British physicists accepted the undulatory theory in the mid-1830s a few emissionists in Britain did not immediately surrender. They continued to fight a rear-guard action against the undulatory theory, hoping that someday they could reinstate their theory.’ The longevity of the confrontation between the emission and the undulatory theory is consistent with recent philosophical and sociological accounts of science, which expect scientific controversy to last a considerable time. Lakatos’s philosophical account, for example, holds that a degenerating theory does not disappear immediately and may revive at any time through a burst of ‘heuristic power’. But this account only allows one universal standard-the verification of excess empirical content-as the basis for both the generation and the closure of scientific controversies.’ On the other hand, sociological accounts such as actor-network theory have also done much to dispel the impression that rapid closure is inevitable in scientific controversies. But perhaps they risk a new orthodoxy: that controversy itself is inevitable.

I propose a new perspective with which to understand scientific revolutions. This is a conversion from an object-only perspective to one that properly treats object and process concepts as distinct kinds. I begin with a re-examination of the Copernican revolution. Recent findings from the history of astronomy suggest that the Copernican revolution was a move from a conceptual framework built around an object concept to one built around a process concept. Drawing from studies in the cognitive sciences, I then show that process concepts are independent of object concepts, grounded in specific regions of the brain and involving unique representational mechanisms. There are cognitive obstacles to the transformation from object to process concepts, and an object bias—a tendency to treat processes as objects—makes this kind of conceptual change difficult. Consequently, transformation from object to process concepts is disruptive and revolutionary. Finally, I explore the implications of this new perspective on scientific revolutions for both the history and philosophy of science.Keywords: Scientific revolutions; Process concepts; Object concepts; Object bias; Copernican revolution.

Thomas Kuhn's Structure of Scientific Revolutions became the most widely read book about science in the twentieth century. His terms 'paradigm' and 'scientific revolution' entered everyday speech, but they remain controversial. In the second half of the twentieth century, the new field of cognitive science combined empirical psychology, computer science, and neuroscience. In this book, the theories of concepts developed by cognitive scientists are used to evaluate and extend Kuhn's most influential ideas. Based on case studies of the Copernican revolution, the discovery of nuclear fission, and an elaboration of Kuhn's famous 'ducks and geese' example of concept learning, this volume, first published in 2006, offers accounts of the nature of normal and revolutionary science, the function of anomalies, and the nature of incommensurability.

Drawing on the results of modem psychology and cognitive science we suggest that the traditional theory of concepts is no longer tenable, and that the alternative account proposed by Kuhn may now be seen to have independent empirical support quite apart from its success as part of an account of scientific change. We suggest that these mechanisms can also be understood as special cases of general cognitive structures revealed by cognitive science. Against this background, incommensurability is not an insurmountable obstacle to accepting Kuhn's position, as many philosophers of science still believe. Rather it becomes a natural consequence of cognitive structures that appear in all human beings.