Studies in History and Philosophy of Science 40 (2009) 210–212

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Studies in History and Philosophy of Science

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Discussion

A curious disagreement: response to Hoyningen-Huene and Oberheim

Howard SankeySchool of Philosophy, Anthropology and Social Inquiry, University of Melbourne, Parkville, Victoria 3010, Australia

a r t i c l e i n f o

Keywords:Scientific realism

IncommensurabilityMeta-incommensurabilityPaul Hoyningen-Huene

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E-mail address: chs@unimelb.edu.au

a b s t r a c t

In this response, doubts are expressed relating to the treatment by Hoyningen-Huene and Oberheim ofthe relation between incommensurability and content comparison. A realist response is presented totheir treatment of ontological replacement. Further questions are raised about the coherence of theneo-Kantian idea of the world-in-itself as well as the phenomenal worlds hypothesis. The notion ofcommon sense is clarified. Meta-incommensurability is dismissed as a rhetorical device which obstructsproductive discussion.

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1. Introduction

In ‘Scientific realism and the semantic incommensurabilitythesis’ (Sankey, 2009), I revisit the exchange which began withthe review by Paul Hoyningen-Huene, Eric Oberheim and HanneAndersen of my book, The incommensurability thesis. I am gratefulto Hoyningen-Huene and Oberheim (henceforth, HHO) for theircomments on my paper (Hoyningen-Huene & Oberheim, 2009).Ever the optimist, I see more progress in this exchange than theirconcluding section suggests. Despite this, their continued talk ofmeta-incommensurability remains unproductive.

Rather than rebut the claims of HHO in ‘point-by-point’ fashion,I concentrate on the main themes that emerge from their com-ment. This should not be taken to indicate tacit agreement onmy part to the points that remain unaddressed here. A similar re-mark applies to matters of minor misunderstanding which are leftuncorrected. In an exchange such as this, some distortion of mes-sage is inevitable.

2. Incomparability of content and rational theory choice

In my paper, I distinguish between semantic incommensur-ability and methodological incommensurability. The former isdue to the semantic variation of the vocabulary employed by the-ories. The latter is due to variation in the methodological standards

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employed by scientists in the evaluation of theories. It is onlythe semantic form of incommensurability that is of relevancehere.

As indicated in my paper, methodological incommensurabilityraises a problem for rational theory choice. However, in theircomment HHO emphasize content comparison and the rationalcomparison of theories, both of which relate to rational theorychoice. While this was not the focus of my paper, it is importantto note that semantic incommensurability does lead to a problemof rational theory choice in its own right. For if, to put the point inan extreme form, alternative scientific theories are expressedusing vocabulary that is entirely semantically variant, then it isnot possible for claims about the world entailed by one theoryto either assert or deny the same thing as any claim of the alter-native theory. Their content is incomparable. But if their contentcannot be compared, then it is not possible to conduct an empir-ical test of any of the competing consequences of the theories.Indeed, it is completely unclear why such theories should betaken to constitute rivals between which a choice is to be madein the first place.

The standard response to the semantic incommensurability the-sis is to point out that terms may vary with respect to sense butshare the same (or overlapping) reference. Provided sufficientcommonality of reference, the assertions of semantically varianttheories may enter into relations of agreement or disagreement.Thus, the incomparability of the content of theories does not follow

H. Sankey / Studies in History and Philosophy of Science 40 (2009) 210–212 211

from semantic variation of the vocabulary employed to express thetheories.

HHO attempt to show that semantic incommensurability doesnot entail incomparability of content by appeal to Kuhn’s and Fey-erabend’s views on the issue. From the point of view of the philos-ophy of method, this is welcome news. For it removes the threatposed by incommensurability to rational theory choice. But diffi-culties arise in reconciling the claim that the content of incommen-surable theories may be compared with what Kuhn andFeyerabend actually say about the matter.

According to HHO, Feyerabend held that incommensurabletheories may be compared and that crucial experiments may beconducted between such theories. But in their discussion in Sec-tion 2.1, HHO are careful not to assert that Feyerabend held thatthe content of incommensurable theories may be compared. Thiscannot be an oversight on their part. Feyerabend addressed theissue repeatedly. For example, in an exchange with Shapere,Feyerabend agreed that incommensurable theories are unable tocontradict each other since they lack ‘identical constituents’(Feyerabend, 1981, p. 115). For another example, Feyerabend con-trasted his views with Kuhn’s by saying that incommensurabletheories in his sense are ‘deductively disjoint’ (Feyerabend,1978, pp. 67–68). They may be compared, but not by means ofcontent (ibid., p. 68). The issue of ‘deductive disjointness’ is theissue adverted to by HHO at the end of Section 2.1 of theircomment.

But, while HHO tacitly recognize that Feyerabend took the con-tent of incommensurable theories to be incomparable, they fail toappreciate the deep problem that undermines his position: theproblem of rivalry. The question that was never resolved by Fey-erabend is how theories that share no content are able to consti-tute genuinely alternative theories in the first place. On thereferential approach, this question is resolved because the claimsmade by semantically variant theories contain terms which eitherco-refer or enter relations of referential overlap. But if the referen-tial approach is rejected, as it seems to have been by Feyerabend,then the basis for such rivalry remains completely mysterious.Nor is the situation improved by appeal to the incompatibility ofincommensurable theories. For the sense in which semanticallyincommensurable theories may enter into a relation of incompati-bility likewise resists explanation. (For details, see Sankey, 1994,pp. 11–16.)

As for Kuhn, it is important to note a key difference between hisview and that of Feyerabend. At least in his later works, Kuhn wasclear that meaning variance was localized. It is restricted to a cen-tral complex of interdefined terms within the special vocabulariesof theories. The localization of the translation failure that resultsenabled Kuhn to meet important objections about the intelligibilityof alternative conceptual schemes. Of more immediate relevance,the local nature of incommensurability means that some of thecontent of incommensurable theories may be directly comparedusing common vocabulary that is shared across incommensurabletheories (Kuhn, 2000, p. 36).

Despite this, unclarity surrounds the notion of ‘point-by-pointcomparison’ that HHO invoke. Kuhn himself noted that:

In applying the term ‘incommensurabilility’ to theories, I hadintended only to insist that there was no common languagewithin which both could be fully expressed and which couldtherefore be used in a point-by-point comparison betweenthem. (Ibid., p. 189)

HHO understand ‘point-by-point comparison’ as ‘comparison ofevery empirical prediction of one theory with a correspondingempirical prediction by the other’ (Hoyningen-Huene & Oberheim,2009, Sect. 2.2). But, if this is what is meant by ‘point-by-point com-parison’, it is unclear why absence of a common language is of any

relevance. If one reads the expression in its original context in theabove quote, it makes better sense to interpret failure of point-by-point comparison as inability to directly compare content dueto absence of shared vocabulary.

But the real issue is not the exegetical question of how best tointerpret the often obscure writings of Kuhn and Feyerabend. Thereal issue relates to the significance of incommensurability forthe methodology of science. If incommensurability entails incom-parability of content, then it poses a threat to rational theorychoice. If it does not entail incomparability of content, then it raisesno issues of any significance for the methodology of science. ButHHO hold that incommensurability retains interest even if it doesnot entail incomparability of content. They think it has implica-tions for scientific realism.

3. Realism, ontological replacement and the progress of science

The primary threat to scientific realism posed by semanticincommensurability relates to the progress of science rather thanthe rationality of theory choice. For if successive theories do not re-fer to the same entities, then it is not possible for later theories toincrease the truth known about the same entities as those referredto by previous theories. But, if semantic incommensurability beto-kens referential discontinuity, it threatens progress in the realistsense. In Section 2.3, HHO assert that this is the ‘genuine threat’that incommensurability presents for realism.

To support their claim, HHO allege that I equivocate betweenthe ‘claim that the terms employed by theories can be used torefer to some of the same entities in predictions, and the claimthat theories themselves refer to the same entities’. They then pro-ceed to note that ‘just because the terms can be used to refer tosome of the same things in specific assertions used to test thosetheories, it does not follow that the terms as used to state thetheories refer to the same kinds’. Oddly, the distinction of whichHHO avail themselves here is itself a tool taken from the realist’stool kit.

It is necessary to exercise care in speaking about reference inthe present context. Two points are of crucial relevance. First, itneeds to be decided whether the entities to which a term purport-edly refers have to exist in order for the term to genuinely refer. AsI (and many, if not most, realists) use the term, ‘refer’ is a successterm. One cannot refer to an entity that does not exist. As I use theterm ‘refer’, the term ‘phlogiston’ did not refer because it did notsucceed in referring to anything real that actually exists. Second,following Kitcher (1978), we need to distinguish between the ref-erence of different tokens of a term-type. Tokens of the term ‘phlo-giston’ for which reference was fixed by description in thephlogiston theory fail to refer, since nothing satisfies the relevantdescription. Some tokens of the term were employed on specificoccasions to refer to specific samples of a gas (for example hydro-gen). Those tokens did refer to the kind actually instantiated by thesample. This is the familiar point made by Kitcher that HHO acceptin their paper.

The trouble is that this is a realist position. So it is hard to seewhy it poses a ‘genuine threat’. There is no need to admit thatthe terms of theories such as the phlogiston theory were genuinelyreferential, as HHO seem to think. Where reference was fixed bytheoretical description, tokens of terms such as ‘phlogiston’ and‘dephlogisticated air’ failed to refer. But because phlogistic chemis-try was applied to the same domain of objects and phenomena asthe oxygen theory, tokens of some phlogistic terms were applied tosome of the same things as oxygen terms were. Application of to-kens of terms to the same domain is all that is needed to comparewhat one theory says about the world with what another theorysays about it.

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4. Neo-Kantian incoherence continued

In my paper, I object to the incoherence of the neo-Kantian ideaof an unknowable world-in-itself and I point out the non-empiricalnature of the hypothesis of phenomenal worlds. In Section 3 oftheir comment, HHO provide an elaborate response to theseobjections.

HHO attempt to block the charge of incoherence by claimingthat the world-in-itself is ‘postulated’ rather than known to exist.But this only raises further questions. Consider what follows ifone postulates the existence of the world-in-itself. Suppose thatit is true that the world-in-itself exists. Then, in postulating theworld-in-itself one succeeds in referring to the world-in-itself.But if one can refer to the world-in-itself, then one can believe thatthe world-in-itself exists. Moreover, if one has reason to postulatethe existence of the world-in-itself, then one has reason to believein the existence of the world-in-itself. Hence, it is true that theworld-in-itself exists, one believes the world-in-itself exists, andone has reason to believe that the world-in-itself exists. Thereforeone knows that the world-in-itself exists. In short, the retreat topostulation fails to avoid commitment to knowledge of theunknowable.

HHO assert that the incoherence is avoided because ‘Postulatingthe existence of the world-in-itself with certain properties is notincoherent with the idea that one does not have epistemic accessto this world-in-itself beyond what one has postulated’(Hoyningen-Huene & Oberheim, 2009, Sect. 3). But if all that is pos-tulated is a world-in-itself about which nothing further is said be-yond that it exists, the postulation is vacuous. Without attributingsome properties to the world-in-itself it can play no explanatoryrole, so cannot be arrived at by an inference to best explanation,as suggested by HHO. If, on the other hand, further properties areattributed to the world-in-itself, over and above mere existence,then it is not clear why it should be regarded as unknowable inthe first place.

As for phenomenal worlds, HHO deny that their existence is amatter of a psychological hypothesis. HHO say that a phenomenalworld is a ‘real world’ that is ‘not only made up of purely object-sided factors . . . but also of genetically subject-sided contributions’(ibid.). But the question arises of where phenomenal worlds are lo-cated. Do they reside within our skulls? Are they outside ourheads? If neither, then what sort of existence do they have? Weare assured, on the one hand, that phenomenal worlds are not the-oretical entities of empirical psychology, and, on the other hand,that the position is not one of subjective idealism. It remains un-clear exactly what ontological status phenomenal worlds enjoy,and on what basis we should believe in them.

According to HHO, Kuhn and Feyerabend were led by an infer-ence to the best explanation to postulate the existence of multiplephenomenal worlds to make sense of the history of science. Butthere is a more plausible explanation of the history of science,namely, that scientists modify their beliefs and concepts as theyapply theories to observed phenomena within an objective reality.Nothing has been said to show that the hypothesis of multiple phe-nomenal worlds is a better explanation than that of realist com-mon sense.

5. Common sense and meta-incommensurability

Mention of common sense brings me to the final two issues thatI wish to address in this response: the issues of common sense andmeta-incommensurability. I start with the latter.

In this exchange, the claim of meta-incommensurability hasfunctioned as an argument stopper. Rather than advancediscussion of the problem of incommensurability, it has been em-ployed as a rhetorical device to stifle debate. To the claim thatincommensurability poses no threat to realism given continuityof reference, it is replied that this begs the question on behalf ofa realist view of reference. To the claim that one must groundmetaphysics in commonsense realism, it is replied that this begsthe question against the Kantian who impugns common sense. Inthe end, the debate goes nowhere, and incommensurability livesto see another day.

In this context, the tu quoque response that I presented in theform of a dilemma has paid dividends. It has flushed from coversomething that resembles an argument. We are now told thatthe neo-Kantian version of the incommensurability thesis is basedon an inference to the best explanation of the ‘historical phenom-enon of incommensurability’ (ibid.). Apart from the fact that it begsthe question to assume the existence of a phenomenon of incom-mensurability, we are owed the details of this inference to the bestexplanation. As we have just seen in the preceding section, theneo-Kantian position must be shown to provide a better explana-tion of the facts of the history of science than the competition. Ofmost present relevance is the competing explanation of scientificrealism, which is grounded in a commonsense attitude towardthe world around us.

As for common sense, HHO provide a list of cases where theytake science to reject common sense. They describe science as a‘struggle against common sense’ and conclude that ‘common sensehas no particularly firm credentials in philosophy’ (ibid.).

All of their examples miss the point. Common sense is more ba-sic than any of their examples. David Armstrong speaks of ‘bedrockcommon sense’, which tells us, for example, that ‘human beingshave heads on their bodies, and hands and feet’ and that we ‘livein a world that contains, besides man-made things, other objectssuch as trees, rivers, mountains, winds, fires’ (Armstrong, 2004, p.27). He calls facts such as these ‘general Moorean truths’. And hesays that ‘a good rough test for the members of this class is thatit is almost embarrassing to mention them outside the context ofphilosophy’ (ibid., p. 27). In addition, there are ‘particular Mooreantruths’, examples of which are the immediate facts of our physicalsurroundings, such as that I am typing these words now sittingnext to an open window.

It will come as no surprise that my final point is an ad hominemone. I know Eric and I know Paul. I know that they have heads ontheir shoulders, and they know this too. In their daily actions, theylive and work in a world of objects that exist independently of theirminds. They, too, are commonsense realists, but they are in denial.

It is a most curious disagreement indeed.

References

Armstrong, D. M. (2004). Truth and truthmakers. Cambridge: Cambridge UniversityPress.

Feyerabend, P. K. (1978). Science in a free society. London: New Left Books.Feyerabend, P. K. (1981). Philosophical papers, Vol. 1. Realism, rationalism and

scientific method. Cambridge: Cambridge University Press.Hoyningen-Huene, P., & Oberheim, E. (2009). Reference, ontological replacement

and Neo-Kantianism: a reply to Sankey. Studies in History and Philosophy ofScience, 40(2), 203–209.

Kitcher, P. (1978). Theories, theorists and theoretical change. The PhilosophicalReview, 87, 519–547.

Kuhn, T. S. (2000). The road since Structure. Chicago: University of Chicago Press.Sankey, H. (1994). The incommensurability thesis. Aldershot: Avebury.Sankey, H. (2009). Scientific realism and the semantic incommensurability thesis.

Studies in History and Philosophy of Science, 40(2), 196–202.