Thomas Kuhn’s Late Incommensurability Thesis as a Wittgensteinian Pragmatism
This paper explores Thomas Kuhn’s mature conception of incommensurable theories as collective structured lexicons that are not mutually translatable. As will be argued, his view on this issue can profitably be approached in the light of the broad pragmatist attitude that one finds at the core of Wittgenstein’s late philosophy of language, which can also consistently be ascribed to Kuhn.
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2These observations are of interest insofar as they represent the starting point of Kuhn’s late attempt to develop a new theory of meaning. In his reply to nine papers inspired by or about his work and discussed at a two-day conference held at MIT in May 1990, Kuhn claimed that

a lexicon or lexical structure is the long-term product of tribal experience in the natural and social worlds, but its logical status, like that of word meanings in general, is that of convention. Each lexicon makes possible a corresponding form of life within which the truth or falsity of propositions may be both claimed and rationally justified, but the justification of lexicons or of lexical change can only be pragmatic. (Kuhn 2000 [RSS]: 244)

3This excerpt gives us a hint as to how the issue of the logical status of lexicons and of word meanings might be approached and unpacked. On the one hand, the connection between the notion of a “lexicon” and that of a “form of life” leads us to a purely Wittgensteinian framework. This is even clearer insofar as Kuhn’s definition of form of life is consistent with what Wittgenstein famously argues, e.g., in the Philosophical Investigations (e.g. Wittgenstein 1958 [PI]: §241) and On Certainty (e.g. Wittgenstein 1969 [OC]: §94 and 162), namely that a form of life is the frame of reference “within which the truth or falsity of propositions may be both claimed and rationally justified.” On the other hand, the justification of lexicons and of lexical change is a matter of pragmatic assessment, for Kuhn. On his view, it would seem to be impossible to provide a purely theoretical justification; in order to appraise the lexicon’s value, one must consider the practical plane of actual deployment. Thus, both the Wittgensteinian and the pragmatist elements seem to be relevant to appreciating Kuhn’s view on the issue of lexicon change – and thus his conception of incommensurability. That is to say, an investigation that explores Kuhn’s late incommensurability thesis in the light of Wittgenstein’s conception of language games, on the one hand, and that stresses the pragmatist feature(s) of Kuhn’s attempted theory of meaning, on the other, might provide an important contribution to Kuhn studies. Yet we should also note that the two abovementioned elements can in fact be merged, given that Wittgenstein’s view of forms of life, language games and world-pictures can be conceived of in a pragmatist fashion based on the idea that, for him, the meaning of a word is a matter of an instrumental assessment of its actual use (cf. e.g. Wittgenstein 1958 [BB]: 56, and 67; PI: §43). Along with this view, I would like to argue that a profitable approach to Kuhn’s mature philosophy consists in reading it through the lens of what I will call a “Wittgensteinian pragmatism.”

4In the following, I will elaborate on these tentative ideas and develop them separately. First, I will explore the issue of incommensurability and/as untranslatability in the late Kuhn (sec. 1). I will therefore say something about Kuhn’s interest in and engagement with Wittgenstein, on the one hand, and pragmatism, on the other, based on the relevant literature available (sec. 2). I will then provide a definition and general outline of what I call “Wittgensteinian pragmatism” (sec. 3). Finally, I will try to show that Kuhn’s late incommensurability thesis is consistent with a pragmatist approach of this sort (sec. 4).

1. Incommensurability and Untranslatability

5Kuhn’s late incommensurability thesis is expounded in a series of papers written in the mid-1980s, where Kuhn presents the core ideas that he intended to include in his unfinished book The Plurality of Worlds. In these texts, Kuhn leaves to the side (almost completely) the pivotal notion of The Structure of Scientific Revolutions – that is, the concept of a “paradigm” – while further working on the view that was originally linked to this notion, trying to approach it from a different angle. The idea of a “paradigm shift” is in fact re-oriented towards the view that different scientific communities – which may be communities arising from different cultural backgrounds, but also communities that pertain to different historical phases within a culture – work with structured lexicons that may be quite distinct from each other. Accordingly, Kuhn tries to reflect on the phenomena of “change in descriptive language” and the “alteration […] of the lexicon which one uses” to describe the world, both of which are implied by the development of science (Kuhn 2022: 15). It is at this level that we encounter what Kuhn previously labelled “manifestations of incommensurability.” As Kuhn explains, “because the use of certain words has changed, some of the statements that recur in the texts of an older science cannot be translated in[to] the language of a subsequent science, at least not with the precision required to understand why they were made” (ibid.). Although we can grasp what the members of a past community or of a community other than our own are conveying with their statements, it is impossible for us to acquire a complete understanding of them. In order to properly understand what they are saying, we need to share their cultural background and the ontology implied by it. When we translate these statements into our own lexicon, we inevitably change them, even if we use the same words as those found in the original sentence. By transferring these words into another frame of reference, we interpret them differently than their original speakers did. In other words, their meaning changes depending on the cultural framework in which the sentence is uttered.

6What Kuhn tries to argue in his late writings can be summed up by the claim that incommensurability means untranslatability. In the second of the three Shearman Memorial Lectures collectively titled The Presence of Past Science (1987), Kuhn in fact argues that incommensurability can fruitfully be compared to the experience of a historian who is struggling to understand a conceptually alien past: “Applied to the relation between successive scientific theories, incommensurability meant no common lexicon, no set of terms with which all components of both theories could be fully and precisely stated” (Kuhn 2022: 51-2). Borrowing a term used by Quine in his Word and Object, Kuhn also says that the word untranslatable might better capture what he has in mind than incommensurable (ibid.: 52). In fact, “incommensurable” stands for the difficulty one encounters “when translating from one language to another but also when translating between earlier and later versions of the same language” (ibid.); in both cases, it is impossible to convey all of the information contained in a sentence, for something will always be left out in the process. As Kuhn argues in his unfinished book The Plurality of Worlds, a statement made in a new lexicon will always be a different statement than one made in the old lexicon. It doesn’t matter whether we are using the same vocabulary; the only way for us to understand the old statement is to learn the incommensurable parts resting at the core of that linguistic expression (cf. ibid.: 114). As noted above, it is the meaning of the words that changes in different historical or cultural contexts. Thus, for example, the sentence “The sun is a planet” would sound quite different to an ancient Greek than to a modern scientist, because they endorse two distinct cosmologies. Their lexicon is different; therefore, they speak of and conceive of the universe differently. Although modern people may comprehend what the Greek scientist is saying, they will never truly understand how the other looks at the world (cf. ibid.: 62).

8Within the picture of incommensurability that Kuhn outlines in his late philosophical remarks, we can stress certain features that connect his view with both Wittgenstein and the pragmatist tradition, namely (a) the idea that each structured lexicon conveys an ontology and evades an epistemic view, and (b) an instrumentalist or conventionalist conception of meaning. Allow me to briefly elaborate on this.

9At the beginning of this paper, I noted that Kuhn claims that “each lexicon makes possible a corresponding form of life within which the truth or falsity of propositions may be both claimed and rationally justified” (RSS: 244). I would like to say that this Wittgensteinian language is used quite aptly in this passage and that it is helpful for appreciating what Kuhn has in mind. In fact, similarly to what we find in famous passages from Wittgenstein’s Philosophical Investigations and On Certainty, in his late writings Kuhn maintains that each lexicon provides us with a set of kind terms that determines the meaning of the vocabulary we can use to describe the world. In other words, each lexicon defines the boundaries of our world-description and represents the frame of reference of any meaningful discourse about it that we can perform within our community. This view is expressed quite clearly in the Sherman Memorial Lectures, where Kuhn argues, for example, that the terms in which the beliefs of a scientific community are stated “carry the community’s ontology, supplying names for things which its world can and cannot contain” (Kuhn 2022: 47). Thus, the language sets the stage of what can or cannot be meaningfully stated; it determines what pertains to our world-description and what remains outside of it. The acquisition of a lexicon is therefore a process that determines how knowledge claims are assessed; better, it is a process that determines what can be counted as “knowledge” (cf. ibid.: 48, and 59). The classic issues of normal science and scientific revolutions are reinterpreted accordingly in the late Kuhn: scientists normally commit to a lexicon that provides them a “set of possible worlds, worlds which share natural kinds and therefore share an ontology” (ibid.: 70). That lexicon brings with it restrictions on what phenomena can and cannot be (that is, of what is “right” or “wrong,” “true” or “false”); “if nature were later found to violate those restrictions […] the lexicon itself would be threatened. Elimination of the threat required not simply the substitution of new beliefs for old but alteration in the lexicon with which the prior beliefs were stated” (ibid.: 49). Thus, a revolution in science is a substitution in the adopted lexicons. But this amounts to a substitution of a form of life, or, in Wittgensteinian terms, of a world-picture (I will say more on this in section 3). This is precisely the case, for Kuhn: with the lexicon, the entire possible (i.e. communicable) world is substituted.

11Lexicons are a prerequisite for the assessment of truth and falsehood; without them, without a background against which to distinguish between true and false, these two terms have no meaning. Accordingly, lexicons cannot be judged as true or false. Insofar as they are the context within which and with reference to which we perform our evaluations, there is no rational basis for assessing their value. Thus, as Kuhn remarks in 1993: “The justification of lexicons or of lexical change can only be pragmatic” (RSS: 244).

12From what has been said thus far, connecting Kuhn’s late views with Wittgenstein’s, on the one hand, and with the pragmatist tradition, on the other, seems like a viable approach. Kuhn’s late incommensurability thesis apparently endorses features from both traditions. In order to say something conclusively on this, however, we must take a step back and investigate the extent to which such a comparison can be made and whether it can actually shed light on Kuhn’s mature philosophy. What I will try to argue in the next sections is not only that this is the case, but that it is through the lens of a view that merges the Wittgensteinian conception of forms of life and world-pictures with the broad pragmatist feature endorsed by Kuhn that Kuhn’s late thought can be profitably interpreted.

2. Kuhn, Wittgenstein, and Pragmatism

13The relationship between Kuhn and the work of the late Wittgenstein, on the one hand, and his relationship with American pragmatism, on the other, has been explored by the literature, albeit scarcely. Very briefly, we can say that there is general agreement that Kuhn was influenced by both traditions and that approaching his thought in their light may be especially beneficial for interpreting his mature philosophy. On this, I would like to endorse the following remark by Vasso Kindi (2017: 597):

Wittgenstein’s influence on Kuhn has been very little discussed in the literature. There have been some sporadic references and very few more extensive treatments of the issue (Kindi 1995, also Sharrock & Read 2002). If, however, the Wittgensteinian elements in Kuhn’s work were brought to bear on the debates that followed Structure, then issues that have been proven highly controversial (and “incriminating” for Kuhn), such as the issue of conceptual incommensurability, would have been dealt with rather differently.

15The main affinity between Wittgenstein and Kuhn that, e.g., Cederbaum and Kindi stress concerns the notions of a paradigm, on the one hand, and language games, on the other. For Cederbaum (1983: 187-9), who was the first to explore this issue, the very concept of “paradigm” is used consistently by both Wittgenstein (e.g. PI: §50) and Kuhn to name concrete examples that permit the solution of certain problems by means of an analogical process. Kindi expanded on Cederbaum’s work and provided a more thorough analysis of the relationship between Kuhn and Wittgenstein, defending “the thesis that the theory of meaning on which Kuhn’s theory is based is supplied by Wittgenstein’s later philosophy” (Kindi 1995: 80). She agrees with Cederbaum that Wittgenstein’s and Kuhn’s notions of a paradigm “are quite close” based on the idea that “they both function as models and prototypes and they both induce and establish consensus by being followed” (Kindi 2017: 596). But the agreement between the two conceptions is actually more substantial, involving the view of meaning that both authors defended. As Kindi argues, interpreting Kuhnian paradigms through the lens of the notion of “language games” helps us to appreciate relevant aspects of the former, namely the fact that paradigms, in Kuhn, operate at the level of practice and that the significance of the concepts adopted in a scientific description of the world are (almost) exclusively determined by the rules that are set by the paradigms themselves. For both Kuhn and Wittgenstein, “paradigms set the stage, open up a space in which things are supposed to be done in the way exemplified by the paradigm” (Kindi 2012: 103); therefore, it is because of them that we know how to use the words in our propositions meaningfully. The meaning of each word depends on the rule that is at play at any stage of normal science – that is, it depends on the specific paradigm endorsed at the time, and this will change when that extra- or pre-linguistic framework of reference is substituted by another one.

17Based on what has been explored in the previous section, it is evident that Kindi’s assessment of the similarities between Kuhn’s epistemology in SSR and Wittgenstein’s late philosophy can be extended to Kuhn’s late incommensurability thesis. I will return to this in a moment. Before dealing with it, I would like to say something on the other issue that I believe is relevant to addressing Kuhn’s mature philosophy, namely pragmatism.

20Thus, at the core of Kuhn’s theory of meaning we do find a pragmatic instrumentalism and relativism. Insofar as a lexicon is a frame of reference for what we consistently say in our statements, one that arises not from a theoretical choice but from a practical one, for Kuhn it is impossible to justify the significance of our words on an essentialist basis. The words in our sentences have meaning because they have a function; they have meaning because they are used in fruitful communication, for example, and not because they mirror nature more adequately than other words. This, I think, is the broad pragmatist feature that we can ascribe to Kuhn’s mature epistemology. As a matter of fact, this is also the broad pragmatist feature that can be ascribed to the late Wittgenstein, as I will attempt to show in the next section.

3. Wittgensteinian Pragmatism

21In this paper, I use the term “Wittgensteinian pragmatism” to describe the broad approach to the issue of meaning as a matter of practice rather than mere theory that can be found in Wittgenstein’s late work (PI, BB and OC) and that I think we may consistently ascribe to Kuhn’s mature philosophy. In his observations on language-games, forms of life, and world-pictures, Wittgenstein famously maintains that the meaning of our words lacks an essentialist foundation and can only be justified instrumentally, based on their actual use in communication processes (cf. e.g. BB: 67; PI: §569). For him, meaning is something that we attribute to words; it does not depend on the adequacy of each word to convey the object it denotes (BB: 27, 28, and 69. Cf. also OC: §191). Therefore, we should conceive of the meaning of a word only as “a kind of employment of it” (OC: §61) rather than a feature that can be appreciated in purely theoretical or metaphysical terms.

25The pragmatist feature that may be ascribed to Wittgenstein was also stressed by Sami Pihlström in a 2012 paper. For Pihlström (2012a: §22), pragmatism should be seen first and foremost as an attempt to focus on the humanly contextualized world-representation, which is the only one we can develop. We look at the world from our human standpoint and pronounce our judgements accordingly; therefore, each judgement is value-laden, for it depends on the individual (not necessarily subjective, but also social, cultural, etc.) perspective that represents its frame of reference. Therefore, things have no meaning in themselves, independently of our judgement activity; there is no hidden essence which we might grasp, and the only value we can attribute to states of affairs is a human value that can be assessed only within the boundaries of our inherited background. With this definition of pragmatism in mind, Pihlström (ibid.: §7) finds it “easy to suggest at a general level that Wittgenstein provides us with a ‘pragmatist’ picture of human language-use and meaning,” for his “later philosophy generally can be read as an attempt to show that it is only against the background of our human form(s) of life, our habits of doing various things together in common environments, that meanings are possible.” This pragmatist point, Pihlström continues, “is highlighted by the fact that […] the notion of language [that appears in Wittgenstein] must be construed […] as a genuine human practice within the natural world” and that “the possibility of language and meaning is grounded in […] habits of action whose radical contingency and continuous historical development are among their key features” (ibid.: §9 and 39). Finally, Pihlström (ibid.: §39) stresses that Wittgenstein leaves no room for a “higher standpoint for us to adopt than the humanly accessible perspectives internal to our language-games,” an observation which allows us to further compare Wittgenstein’s view with Kuhn’s and to ascribe to both authors the pragmatist commitment outlined thus far.

4. Lexicons as Forms of Life

26With this broad pragmatist approach in place, and assuming that the influence of the late Wittgenstein on Kuhn is no longer in question, I can finally return to the view of incommensurability as untranslatability explored in section 1. As I will argue, almost all of the features that pertain to Wittgenstein’s notion of a form of life mentioned in the previous section – including, of course, the pragmatist one – may be consistently ascribed to Kuhnian lexicons. Insofar as Kuhn relates incommensurability to lexicons that determine the ontology of a scientific community (that is, of the world that each scientific community is allowed to meaningfully describe and work on), it is possible to argue that his late view of the issue can be fruitfully interpreted in the light of what I have called a Wittgensteinian pragmatism.

29This view and its connection to a pragmatic account of meaning is also defended in the 1987 Shearman Memorial Lecture, where Kuhn argues that “a lexicon cannot properly be labelled true or false,” given that “its structure […] is a matter of social or linguistic fact. […] Instead, one lexicon is a better or worse instrument than another for achieving specifiable social goals, and the choice between lexicons […] necessarily depends on those goals” (Kuhn 2022: 78). In the first section of this paper, I have already mentioned that Kuhn ascribes this instrumentalist view to the Pragmatist tradition; in fact, he argues that “with respect to lexicons […] the pragmatists are generally right. Lexicons are instruments to be judged by their comparative effectiveness in promoting the ends for which they are put to use” (ibid.). In addition to this, the view that the world and the community interact through lexicons has significant ontological consequences. For the late Kuhn, in fact, “essential parts of a community’s knowledge of nature are embodied in the structure of the lexicon which members of the community share”; hence “to acquire a lexicon […] is to learn things about the world” (ibid.: 48; cf. also ibid.: 180). As noted above, what a scientific community can or cannot consistently say of the world, what kinds of phenomena it can or cannot encounter in that world, is determined by the set of linguistic tools acquired within that community’s cultural and historical context. Thus, the structured lexicon actually determines what the world that can be worked on and meaningfully communicated is, for that community, and any change in the lexicon implies changes in both the world and the community (cf. ibid.: 80).

30As a final remark, based on an interpretation of lexicons as forms of life or world-pictures, I would like to stress the continuity that is evident between Kuhn’s late incommensurability thesis and Wittgensteinian pragmatism. As we have seen, for Kuhn a structured lexicon is the background of our evaluations and actions, of our epistemic and practical behaviour – just like a Wittgensteinian world-picture. Much like it, a structured lexicon is the foundation of how scientists look at the world and practically engage it; it is the conceptual environment acquired through education and training within which they work, and which provides the criteria of correctness and – quite importantly – of meaningfulness for their judgements (cf. OC: §167). This allows us to see that both Kuhn and Wittgenstein approached the issue of language with a primary interest in the practical plane of its actual use. As Pihlström remarks (2012a: §39), for Wittgenstein “the possibility of language and meaning is grounded in […] habits of action whose radical contingency and continuous historical development are among their key features.” The very same view can be applied to Kuhn, as I have tried to show: in fact, the structured lexicons that he describes in his late works are contexts of consistent (scientific) activity that are both culturally and historically determined. Furthermore, Kuhn conceives of structured lexicons as an important tool that scientists deploy in their engagement with the world, a view that he stressed repeatedly, thus reiterating the broad pragmatist attitude that characterizes his mature philosophy and whose roots, in my opinion, are firmly Wittgensteinian.