By Vincenzo Politi
Where does the term incommensurability come from? What is its relevance to interdisciplinarity? Is it more than plain difference? Does incommensurability need to be reconceptualized for interdisciplinarity?
Incommensurability: its origins and relevance to interdisciplinarity
‘Incommensurability’ is a term that philosophers of science have borrowed from mathematics. Two mathematical magnitudes are said to be incommensurable if their ratio cannot be expressed by a number which is an integer. For example, the radius and the circumference of a circle are incommensurable because their ratio is expressed by the irrational number π.
In philosophy of science, the term is used in a metaphorical sense: two competing scientific theories, paradigms or research projects are said to be incommensurable when there is no common ground for their rational comparison and choice. The effects of incommensurability become visible during debates surrounding scientific revolutions, when the supporters of two competing paradigms or research projects attach different meanings to the same words, thus ending up experiencing communication breakdowns.
Recently, scholars interested in interdisciplinarity have started to use the concept of ‘incommensurability’ to describe some of the difficulties surrounding interdisciplinary research (see the blog posts by Andi Hess on Two types of interdisciplinary scholarship and Britt Holbrook on Interdisciplinarity and evil – Understanding incommensurability; see also Holbrook 2013). The different disciplines involved in an interdisciplinary project may not share the same vocabulary. In such cases, the specialists working on the project may find themselves in the same situation as scientists talking at cross-purposes during a scientific revolution.
Incommensurability or difference?
Not everybody agrees with the idea that the concept of incommensurability is useful in discussing interdisciplinarity. It may be argued, in fact, that the disciplines involved in an interdisciplinary project are not properly incommensurable, but just different. Incommensurability is more than mere difference: as indicated earlier, philosophers introduced this concept to describe problems associated with the choice between two competing paradigms during periods of revolutionary scientific change. However, many disciplines are not in competition at all, since they are just about different domains.
Since they are not in conflict or in competition, the different disciplines involved in interdisciplinary collaborations can be thought of as complementary, rather than incommensurable. Furthermore, the very existence of interdisciplinary collaboration seems to be evidence against the idea that there is some sort of incommensurable barrier which is an obstacle to cross-disciplinary communication.
This argument urges us to distinguish more sharply between incommensurability and plain difference, since the latter does not necessarily imply the former.
In the same way in which the existence of incommensurability among different disciplines should not be uncritically presupposed, however, the idea that different disciplines are just complementary should not be taken for granted. Whether different specialists can actually integrate their skills, knowledge and styles of reasoning for the resolution of a complex problem can be determined only within the actual context of the problem-solving practice and, often, only after the interdisciplinary collaboration has revealed itself to be fruitful. Different disciplines do not spontaneously ‘fall into place’ by virtue of their being complementary, nor does interdisciplinarity happen by fiat.
Reconceptualising incommensurability for interdisciplinarity
I suggest that there are two key issues relevant to genuine incommensurability in the context of interdisciplinary research (Politi 2017). These require some reconceptualisation of the original ideas about incommensurability.
First, I suggest that incommensurability in this context should not be conceived as an a-temporal, universal and logical relation, as it is in mathematics. Rather, we should look at interdisciplinarity from a dynamical/historical perspective. It is true that different disciplines are not necessarily incommensurable. By virtue of their historical trajectories, however, different disciplines may become incommensurable.
This happens when they end up converging towards an overlapping area of research: after all, the whole idea of interdisciplinarity is founded on the belief that different disciplines may have something to say about a common range of problems. In these cases, (parts of) different disciplines may find themselves offering incompatible (and maybe competing) solutions to problems pertaining a common sub-domain. Each discipline, in fact, may have its own way of conceptualising and modelling such problems and neither effective collaboration nor integration are guaranteed.
Second, I propose that incommensurability should not be regarded as a purely semantic problem affecting communication and arising from the way in which different scientists use the same terms. Finding a way to communicate across specialties may be necessary but not sufficient for successful interdisciplinarity. It is perfectly plausible to suppose that scientists coming from different disciplines may learn each other’s theoretical language and communicate with one another without too many problems. Successful communication, however, does not imply total agreement about the problem-solving methodologies to implement.
It should not be forgotten, for example, that incommensurability also possesses some important methodological aspects. For example, one group of scientists may prefer a theory which is more accurate and consistent, while another group of scientists may prefer a theory which seems to be more fruitful for future research. This type of disagreement has little or nothing to do with problems of translation or with the meaning of scientific terms: two groups may continue to disagree even when they fully communicate and understand each other, without experiencing any ‘communication breakdown’. Incommensurability can also have cognitive or perceptual aspects: different specialists may literally see, and therefore conceptualise, the same problem in different ways.
It makes little sense to speak of incommensurability in absolute and a-historical terms. Rather, incommensurability should be invoked when different disciplines converge towards the same domain. In these cases, mere difference can become incompatibility and competition, that is incommensurability.
Moreover, incommensurability is not only a linguistic problem preventing successful communication. Different scientists may communicate and understand each other very well but, successful communication notwithstanding, they may just ‘agree to disagree’.
What do you think? Do these ideas resonate or do you see things differently?
Holbrook, J. B. (2013). What is interdisciplinary communication? Reflections on the very idea of disciplinary integration. Synthese, 190: 1865–1879
Politi, V. (2017). Specialisation, interdisciplinarity, and incommensurability. International Studies in the Philosophy of Science, 31: 301–317
Biography: Vincenzo Politi PhD is a postdoctoral researcher at CEA – Commissariat à l’énergie atomique et aux énergies alternatives (French Alternative Energies and Atomic Energy Commission) in Paris-Saclay, France. He works on philosophical issues concerning scientific change and on the ethics of science.