The Kuhnian Image of Science

Time for a Decisive Transformation?

Moti Mizrahi

• Publisher: Rowman & Littlefield International
• Year: 2017
• ISBN:
  9781786603425
• Edition: 1
• Topic: Philosophy
• Subtopic: Epistemology in Philosophy

More than 50 years after the publication of Thomas Kuhn’s seminal book, The Structure of Scientific Revolutions, this volume assesses the adequacy of the Kuhnian model in explaining certain aspects of science, particularly the social and epistemic aspects of science. One argument put forward is that there are no good reasons to accept Kunh’s incommensurability thesis, according to which scientific revolutions involve the replacement of theories with conceptually incompatible ones. Perhaps, therefore, it is time for another “decisive transformation in the image of science by which we are now possessed.” Only this time, the image of science that needs to be transformed is the Kuhnian one. Does the Kuhnian image of science provide an adequate model of scientific practice? If we abandon the Kuhnian picture of revolutionary change and incommensurability, what consequences would follow from that vis-à-vis our understanding of scientific knowledge as a social endeavour?
The essays in this collection continue this debate, offering a critical examination of the arguments for and against the Kuhnian image of science as well as their implications for our understanding of science as a social and epistemic enterprise.

Part I

QUESTIONING THE KUHNIAN IMAGE OF SCIENCE

Chapter 1

Kuhn’s Incommensurability Thesis

What’s the Argument?

Moti Mizrahi

1. INTRODUCTION

Since Thomas Kuhn first introduced the incommensurability thesis in 1962, it has undergone several transformations, even in Kuhn’s own writings (Hoyningen-Huene 1993, 206–22).¹ Basically, the thesis has been understood in at least two different ways:

• Taxonomic Incommensurability (TI): Periods of scientific change (in particular, revolutionary change) that exhibit TI are scientific developments in which existing concepts are replaced with new concepts that are incompatible with the older concepts. The new concepts are incompatible with the old concepts in the following sense: two competing scientific theories are conceptually incompatible (or incommensurable) just in case they do not share the same “lexical taxonomy.” A lexical taxonomy contains the structures and vocabulary that are used to state a theory (see Kuhn 2000, 14–15, 63, 92–97, 229–33, 238–39, and 242–44. Cf. Sankey 1997).²
• Methodological Incommensurability (MI): There are no objective criteria of theory evaluation. The familiar criteria of evaluation, such as simplicity and fruitfulness, are not a fixed set of rules. Rather, they vary with the currently dominant paradigm (see Kuhn 1962, 94; 1970, 200; 1977, 322, and 331. Cf. Sankey and Hoyningen-Huene 2001: xiii).³

Kuhn’s incommensurability thesis has generated an enormous literature.⁴ In this paper, I wish to examine the evidence that is supposed to support Kuhn’s incommensurability thesis. This is an important task, I think, for the following reasons. First, some authors use the language of “discovery” when writing about Kuhn’s incommensurability thesis. According to Oberheim and Hoyningen-Huene (2013), for instance, Kuhn “discovered incommensurability in the mid to late 1940s” (emphasis added). This “discovery” was then followed by a change in career paths. Using the “discovery” language in talking about Kuhn’s incommensurability thesis gives the impression that incommensurability is a fact about scientific change (revolutionary change, in particular). But what if one does not think that incommensurability is a fact about scientific change? Are there compelling epistemic reasons to think that the incommensurability thesis is indeed true or probable? In other words, are there good arguments for the incommensurability thesis?

Second, and perhaps as a consequence of the first reason, it seems that the literature has focused more on exploring the implications of Kuhn’s incommensurability thesis than on evaluating the arguments for the thesis itself.⁵ This is not to say that no one has disputed Kuhn’s incommensurability thesis (see, e.g., Scheffler 1982). Arguing that a thesis is false, however, is not the same as arguing that there is neither valid deductive nor strong inductive support for a thesis.

In what follows, I focus on (TI) rather than (MI). Here is how I plan to proceed. In section 2, I argue that there is no valid deductive argument⁶ for (TI), since from the fact that the reference of the same kind terms changes or discontinues from one theoretical framework to another, it does not necessarily follow that these two theoretical frameworks are taxonomically incommensurable. In section 3, I argue that there is no strong inductive argument⁷ for (TI) because there are rebutting defeaters against (TI). That is, there are episodes from the history of science that do not exhibit discontinuity and replacement, as (TI) predicts but rather continuity and supplementation. If this is correct, then there are no compelling arguments in support of (TI). In section 4, I discuss and reply to an objection made by an anonymous referee of the journal Social Epistemology, where this chapter was originally published.

2. WHY THERE IS NO VALID DEDUCTIVE SUPPORT FOR (TI)

Is there deductively valid support for (TI)? That is, is there a valid deductive inference from reference change to incompatibility of conceptual content, and thus to (TI)? By appealing to the distinction between sense and reference, Scheffler (1982, 59–60) has already shown that variation of sense does not entail incompatibility of conceptual content.⁸ In that case, perhaps reference change is supposed to entail incompatibility of conceptual content, and hence taxonomic incommensurability. That is, “Distinct taxonomic structures (ones with different subsumption and exclusion relations) are inevitably incommensurable, because those very differences result in terms with fundamentally disparate meanings” (Conant and Haugeland 2000, 5; emphasis added). Indeed, in his later works, Kuhn talks about reference change as “redistribution” of members among “taxonomic categories” (Kuhn 2000, 30). Such “referential changes,” according to Kuhn (2000, 15), show that “scientific development cannot be quite cumulative,” that “one cannot get from the old to the new simply by an addition to what was already known,” and that one cannot “describe the new in the vocabulary of the old or vice versa” (emphasis added). Furthermore, as Sankey (2009, 197) points out:

Analysis of the reasoning employed by Kuhn […] when [he] argue[s] for […] reference change reveals that [he] assume[s] that reference is determined by description.

Accordingly, I take it that a deductive argument for (TI) would run roughly like this:

• (TI1) If competing theories were taxonomically commensurable, then terms would still refer to the same things in new theories (e.g., “mass” in Newtonian mechanics and “mass” in relativistic mechanics would have the same referent).
• (TI2) Terms do not refer to the same things in new theories (e.g., “mass” in Newtonian mechanics and “mass” in relativistic mechanics do not have the same referent, and some terms, such as “phlogiston,” are eliminated outright).

Therefore:

• (TI3) Competing theories are taxonomically incommensurable.⁹

In addition to “mass,” another example that is supposed to illustrate how reference change is evidence for incompatibility of conceptual content is the following:

Whereas Ptolemaic astronomers used the term “planet” to denote wandering stars, that is, those “stars” that are not fixed stars, Copernicus used the term “planet” to denote a celestial body that orbits the sun (Wray 2011, 25).

This variation in the referents of the term “planet,” then, is supposed to show that the Ptolemaic model and the Copernican model are conceptually incompatible.

For this argument to be deductively valid, however, (TI3) must follow necessarily from (TI1) and (TI2). The crucial premise is (TI1). The claim here seems to be that T₁ and T₂ are taxonomically commensurable if and only if T₁ and T₂ share the same lexical taxonomy. Sharing the same lexical taxonomy, as we have seen, means that the kind terms that are used to state T₁ and T₂ refer to the same things. That is to say, for (TI1) to be true, the following conditionals would have to hold:

• (C1) If kind terms t refer to X in T₁ and to X in T₂, then T₁ and T₂ are taxonomically commensurable.
• (C2) If kind terms t refer to X in T₁ and to Y in T₂, then T₁ and T₂ are taxonomically incommensurable.

As Hoyningen-Huene (1993, 99) explains, to ensure that they refer to the same things with the same kind terms, scientists need only share vocabularies that incorporate the same taxonomies. If two competing theories do not share the same lexical taxonomies, then those two theories are taxonomically incommensurable (Kuhn 2000, 63).

However, as a general claim about the conceptual incompatibility, and hence incommensurability, of theoretical frameworks,¹⁰ I think that (C2) is false. To see why (C2) is false, consider the following:

• (K1) In biological taxonomy, “kid” refers to a young goat, whereas in folk taxonomy, “kid” refers to a child.

Therefore:

• (K2) Biological and folk taxonomies are taxonomically incommensurable.

Since (K2) seems false, given that “kid” refers to a young goat in the order Artiodactyla but not in the order Primate, and both orders belong to the class Mammalia, even as far as folk taxonomy is concerned, there must be something wrong with the inference from (K1) to (K2). In other words, if the inference from (K1) to (K2) is supposed to be deductively valid, but (K2) is false, and (K1) is true, then it follows that the inference must be invalid after all, since valid inferences with true premises cannot lead to false conclusions. If this is correct, then from the fact that the same kind terms refer to different things in different theoretical frameworks, it does not necessarily follow that these theoretical frameworks are taxonomically incommensurable.¹¹

To put it another way, if reference change were conclusive evidence for incompatibility of conceptual content, and hence for taxonomic incommensurability, then we would have to conclude that folk taxonomy and biological taxonomy are conceptually incompatible, since in the former, “kid” refers to one thing, and in the latter, “kid” refers to something else. But folk taxonomy and biological taxonomy are not conceptually incompatible. Therefore, reference change is not conclusive evidence for incompatibility of conceptual content. That is, there is no valid deductive inference from reference change to incompatibility of conceptual content, which means that there cannot be a valid deductive argument for (TI) from reference change alone.

For Kuhn, revolutionary change consists in the replacement of a lexical taxonomy by another incompatible taxonomy (Wray 2011, 25). That is to say, revolutionary changes violate Kuhn’s (2000, 92) no-overlap principle, according to which:

no two kind terms, no two terms with the kind label, may overlap in their referents unless they are related as species to genus. There are no two dogs that are also cats, no gold rings that are also silver rings, and so on: that’s what makes dogs, cats, silver, and gold each a kind.

Individuating kind terms, however, is a rather tricky business. Is “puppy” a kind term? If so, “puppy” and “dog” are two kind terms, which overlap in their referents even though they are not related as species to genus. Be that as it may, for present purposes, the important point is that there are no conclusive epistemic reasons to think that scientific change, revolutionary or otherwise, involves abandoning a lexical taxonomy in favor of another incompatible one, given that reference change alone is not conclusive evidence for incompatibility of conceptual content, as the “kid” argument shows.

Proponents of (TI) might insist that deductively valid support for (TI) comes from periods of scientific change in which kind terms are dropped entirely (e.g., “phlogiston”) rather than change their meaning (e.g., “mass”). In other words, it is not reference change (i.e., when the referents of kind terms change) that entails incompatibility of conceptual content but rather reference discontinuity (i.e., when kind terms no longer refer because they were abandoned).¹² In that case, the claim expressed by (TI1) would be that T₁ and T₂ are taxonomically commensurable if and only if the same kind terms from T₁ are retained in T₂. That is to say, for (TI1) to be true, the following conditionals would have to be true:

• (C3) If kind terms t are used in T₁ and retained in T₂, then T₁ and T₂ are taxonomically commensurable.
• (C4) If kind terms t are used in T₁ but dropped in T₂, then T₁ and T₂ are taxonomically incommensurable.

However, as a general claim about the conceptual incompatibility, and hence incommensurability, of theoretical frameworks,¹³ I think that (C4) is false. To see why (C4) is false, consider the following:

• (M1) In desktop environment, WIMP refers to a user interface that includes windows, icons, menus, and pointer, whereas in tablet environment, WIMP has been dropped entirely.

Therefore:

• (M2) Desktop environment and tablet environment are taxonomically incommensurable.

Since (M2) is false, given that the same theoretical principles of computing govern the operation of both desktops and tablets, there must be something wrong with the inference from (M1) to (M2). In other words, if the inference from (M1) to (M2) is supposed to be deductively valid, but (M2) is false, and (M1) is true, then it follows that the inference must be invalid after all, since valid inferences with true premises cannot lead to false conclusions. If this is correct, then from the fact that kind terms have been abandoned by a later theoretical framework, it does not necessarily follow that the earlier and the later theoretical frameworks are taxonomically incommensurable.

In fact, even in the case of “phlogiston,” it is not obvious that the two competing theories in question are indeed taxonomically incommensurable. Applied to the case of “phlogiston,” the alleged inference from reference discontinuity to taxonomic incommensurability would run roughly as follows:

• (P1) In Stahl’s theory of combustion, “phlogiston” refers to the substance that is responsible for combustion, whereas in Lavoisier’s theory of combustion, “phlogiston” is dropped and “oxygen” refers to the gas required for combustion.

Therefore:

• (P2) Stahl’s theory of combustion and Lavoisier’s theory of combustion are taxonomically incommensurable.

But (P2) does not necessarily follow from (P1). To see why, suppose that Stahl’s theory of combustion is true, and so there is phlogiston, which is the substance that is responsible for combustion. But it could still be the case that there is oxygen as well. In fact, it might actually be a useful addition to Stahl’s theory of combustion, since one of its problems was to explain why, when some metals were calcined, the resulting calx was heavier than the original metal. Some tried to explain this by saying that, in some metals, phlogiston has negative weight. Instead, they could have said that phlogiston is lost but oxygen is gained, which would have explained the heavier weight.¹⁴

If this is correct, then, contrary to the claim that Stahl’s theory of combustion and Lavoisier’s theory of c...

Table of contents

• Introduction
• Part I: Questioning the Kuhnian Image of Science
• Part II: Defending the Kuhnian Image of Science
• Part III: Revising the Kuhnian Image of Science
• Part IV: Abandoning the Kuhnian Image of Science
• Index
• About the Editor
• About the Contributors