Studies in History and Philosophy of Science 49 (2015) 91e98

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The Chemical Revolution revisited Hasok Chang Department of History and Philosophy of Science, University of Cambridge, Free School Lane, Cambridge CB2 3RH, United Kingdom

a r t i c l e i n f o

a b s t r a c t

Article history: Available online 26 December 2014

I respond to the critical comments by Martin Kusch and Ursula Klein on my account of the Chemical Revolution. I comment along three different lines: descriptive, explanatory, and normative. (1) I agree with Klein that Lavoisier did not introduce drastic changes in chemical ontology, but maintain that there was methodological incommensurability in the Chemical Revolution; in response to Kusch’s view, I maintain that Lavoisier’s victory was slow and incomplete. (2) Admitting that there were many causes shaping the outcome of the Chemical Revolution, including the convenience of Lavoisier’s theoretical scheme and various complicated social factors, I still think that the general rise of compositionism was an important factor. (3) I defend my normative pluralist view on the Chemical Revolution, denying Kusch’s argument that chemists had overwhelmingly good reasons to trust Lavoisier and his allies over the phlogistonists. Overall, I agree with Kusch that it would be desirable to have a good descriptiveenormative sociological account of the Chemical Revolution, but I also think that it should be an account that allows for divergence in individuals’ and sub-communities’ self-determination. Ó 2014 Elsevier Ltd. All rights reserved.

Keywords: Chemical Revolution; Phlogiston; Incommensurability; Compositionism; Pluralism

When citing this paper, please use the full journal title Studies in History and Philosophy of Science

1. Introduction It is a great honour to have my work critically examined in such depth and detail by two of the scholars that I respect most, and to have an opportunity to re-examine my own views. I would like to begin by summing up the spirit of my response. With Ursula Klein’s description of the event usually known as the Chemical Revolution, I actually have no significant disagreements; however, convincing her (and others) of that will be an interesting challenge. Concerning Martin Kusch’s points I do have some disagreement, and my challenge there is to render the disagreement productive, as he also wishes to do. I have organized my comments around three different types of critique that Kusch and Klein have raised: the descriptive, the explanatory, and the normative. What exactly did happen in the “Chemical Revolution”? What is the best explanation of why it happened? And was it a good thing that it happened? I will try to argue that the answers I have given to these questions in Is Water

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H2O? and various other publications still stand, but I will also try to indicate where the critique by Kusch and Klein points to lines of research and thinking that I should have pursued further. 2. What happened? Klein and Kusch both find my description of the Chemical Revolution lacking, but in different ways. I will take their critique in turn, and then attempt a summing-up. 2.1. Klein: was there a revolution? Ursula Klein’s main message is that there was no real revolutionary change in the event that historians, philosophers and chemists have often called the “Chemical Revolution”: “If we define scientific revolutions as changes of scientists’ ontologies, types of causal explanation, and paradigmatic types of methods and instruments, Antoine-Laurent Lavoisier’s contribution to chemistry did not amount to a scientific revolution.” (Klein, 2015, in this issue, p. 80, abstract). This contention is based on a very detailed and careful study that she and Wolfgang Lefèvre have made in their

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book Materials in Eighteenth-Century Science (2007). I endorse what they say about Lavoisier in that notable book, and have said so in print, though in a review published in a journal that has little currency in history and philosophy of science (Chang, 2010a). But Klein’s sense of what a revolution should mean is not the only possible one, and the substance of her discussion belies even her own definition of revolution, as her focus is very strongly on the point about ontology. This ontological emphasis does sit well with Thomas Kuhn’s extensional notion of incommensurability from the later years of his life, which focused on cross-cutting boundaries of classificatory categories. However, it is too narrow to fit with Kuhn’s earlier ideas, and it is the early Kuhn of The Structure of Scientific Revolutions that used the Chemical Revolution as one of the prime examples of scientific revolutions.1 I would go along with Klein’s conclusion entirely, if it would be just slightly rephrased as “in such and such respects, Lavoisier’s contribution was not revolutionary.” Kuhn’s original notion of scientific revolutions was broad and imprecise, and his original notion of incommensurability multidimensional. While I agree with Klein that Lavoisier did not introduce such a drastic change in the ruling chemical ontology of the day, I think he did introduce other major changes. I have argued elsewhere (Chang, 2012a) that there was clear methodological incommensurability between the phlogistonist and oxygenist paradigms, though only mild semantic incommensurability. Lavoisier certainly introduced sufficient changes in the problem-field and the judgment-criteria in chemistry, so as to make it difficult to reach paradigm-independent judgments of merit. That difficulty of impartial judgment is exactly what constitutes incommensurability, according to the Kuhn of Structure. And chemical ontology did change a bit, too. First of all, competing sides in the Chemical Revolution disagreed sharply about what counted as elements and what were compounds (metal or calx, sulphur or sulphuric acid, etc.), and this was a difference that was considered very important by many chemists of the time, though it is seen as minor by Klein. In addition, as I will explain further below, phlogistonists did tend to retain the idea of phlogiston as a “principle”, an ontological category that would disappear as Lavoisierian chemistry developed. By the early Kuhn’s lights, there was certainly a revolution here. Besides, the notion of a scientific revolution is not entirely owned by Kuhn, either, and I think it is reasonable to maintain without much harm the “revolution” label in a rather innocent or naïve way, simply meaning “rapid and fundamental change.” Still, we can debate how important ontology at the level discussed by Klein is at the foundation of a science, and think about how ontology affects the rest of scientific practice and knowledge. I think that would be a more productive discussion than trying to decide whether there was a “revolution” or not. There are all kinds and degrees of continuity and discontinuity in scientific change, and it seems to me an important and interesting task for historians of science to discern them carefully.

2.2. Kusch: in defence of Lavoisier’s triumph? Martin Kusch also finds inadequacies in my description of the Chemical Revolution (if we may still use that designation). His critique pulls in a rather opposite direction from Klein’s: while Klein thinks that I (and most others) exaggerate the discontinuity in the history, Kusch seems to chide me for failing to acknowledge the clear-cut triumph of Lavoisier for what it was. (It is not entirely clear to me why this matters so much to Kusch, though I will try to spell out my thoughts on that matter in the last section of this paper.)

1

See Hoyningen-Huene (2008) for the exposition of this point.

One might say that I myself complicated matters unnecessarily by taking an exception to the prevalent descriptions of the Chemical Revolution. It would have been simpler to go along with the usual story that Lavoisier won a quick and nearly unanimous victory, and then put forward my normative pluralist thesis that he should not have. Why did I have to spoil that simple line of argument, by saying that Lavoisier’s victory was actually not as decisive as often believed? Well, I am enough of a historian not to be able accept a description of the past that I see as simply inadequate. It is futile to try to offer an explanation of why something happened, if it didn’t happen. Before I could get seriously down to my business of stating why the event happened and how it should have gone instead, I had to satisfy myself with a description that I could believe. Kusch objects to my description of those who didn’t entirely agree with Lavoisier, whom I classified into three classes (“diehards”, “fence-sitters” and “new anti-Lavoisierians”).2 The point of that rather elaborate story of mine was the following: “there are indeed many senses in which Lavoisier and his colleagues brought about a ‘revolution’ in chemistry, but it was not a sudden and clearcut affair. It was a many-sided struggle that neither ended in unanimous agreement nor established any immutable orthodoxy.” (Chang, 2012b, p. 34). I cannot see why this conclusion is so objectionable to Kusch, and the way he argues against it is not convincing to me. He says I should consider overall numbers, rather than listing some names; doing the overall numbers would be an interesting exercise, but what we are looking at is not a majority vote. He says my account is based on the view that the situation was something of a zero-sum game (or, more like, “you’re either with Lavoisier or with the phlogistonists”) (Kusch, 2015, in this issue, p. 74), but that is precisely the opposite of what I am indicating with the category of “new anti-Lavoisierians” (or, “anti-anti-phlogistonists”), who were neither for phlogiston nor for Lavoisier. And the following is a loose and a rather reductionist statement (Kusch, 2015, in this issue, p. 75): “we should not forget that when the war was over Davy quickly dropped his phlogistonist project.” Davy stopped talking much about phlogiston around 1810, and that does not line up with the end of the war. There is no evidence that he “quickly dropped” the “project”. Most importantly, Davy’s anti-anti-phlogistonist opposition to Lavoisierian chemistry did not end with the war, either; on the contrary, his identification of chlorine as an element was an achievement of which he remained proud, and that was what put an effective end to Lavoisier’s theory of acidity. One thing I will admit is that it would have been better not to include Bergman, Macquer and Scheele in the list of “die-hards”, as my main point was about die-hards that lasted beyond 1790.

2.3. Was there such a thing as the “phlogiston system”? There is one point of descriptive criticism that Kusch and Klein would probably agree on, though only Kusch is explicit about it. This is the complaint that I over-simplified the field of contention in the Chemical Revolution. This is a criticism that I can readily accept, and have actually already anticipated. It was perhaps lazy of me to speak of the “phlogistonist system”. As Kusch notes (2015, in this issue, p. 74), I did emphasize that there were various versions of the phlogistonist system (Chang, 2012b, p. 28). I hope that the recognition of the existence of different versions is shown clearly in various places in my discussion (esp. in Chang, 2010b; Chang, 2012b, Section 1.3.1). It is a very interesting and important task to distinguish the different versions carefully, as some of the leading

2

Further details can be found in Chang (2010b).

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scholars have done. I did not make much of an advance in that direction, but I think I did provide a framework for describing the situation more cogently (Chang, 2011), which would be to say that phlogistonist chemistry was not a single system, but a system-type. On the basis of the phlogiston system-type many different systems were constructed, all of which shared some core activities. What follows from this over-simplification that I made? Admitting the diversity of phlogistonist systems is actually only more grist for my pluralist mill. Provided that the phlogistonist tradition was a productive one (as I argue), its exuberant plurality provides some reassurance that having multiple phlogistonist systems was at least not necessarily the embarrassing fiasco that Lavoisier made it out to be. And even the oxygenist side, despite the tight doctrinal control there, had some variations. (This is, for example, what made me classify Berthollet as a fence-sitter; surely he was a very close ally of Lavoisier, but they did have some important scientific differences, about the theory of combustion and the theory of acidity.) Kusch has a different worry, however, which I do not fully understand. A succinct statement of this worry is given in the concluding section of his paper: correcting the assumption “that uses of ‘phlogiston’ were based on one coherent system of epistemic activities” “weakens Chang’s comparisons and his counterfactual reasoning on what might have been, had the ‘phlogistonist system’ been kept alive longer.” (Kusch, 2015, in this issue, p. 78) I did not suggest that all the different versions of the phlogistonist system would be mutually coherent. I think it would help to prevent misunderstanding if I were to say that phlogistonism was a system-type under which there were various phlogistonist systems. And then I think it also becomes quite unproblematic to make my normative statement that it would have been better to preserve the most promising of the phlogistonist systems. 2.4. Summary of the descriptive situation So, what did happen? Contrary to Klein’s suggestion I think it does make sense to speak of the Chemical Revolution, but not much of importance hangs on the “revolution” label itself. The important thing is to recognize that a significant change took place in chemistry in the late 18th century, and to be sensitive about the exact nature of that change. I agree with Klein that the change concerning chemical ontology was not as drastic or simple as it is often supposed, but I also do not think that ontology is the only important aspect of scientific change. Recognizing the complexity of the Chemical Revolution, I maintain, also involves recognizing the slowness and incompleteness of the “conversion” of the chemical community to Lavoisier’s point of view. Getting a nuanced description of what did happen is quite important as we try to tackle the task of explaining why it happened, which is the subject of the next section. 3. Why did it happen? 3.1. Not because “Lavoisier was right” I trust that Klein, Kusch and I are all agreed that the outcome of the Chemical Revolution was not a simple matter of “right over wrong”, by the criteria of an impartial judge at the time (or even by the criteria of a well-informed modern scientist). I have made detailed arguments to that effect (Chang, 2012b, Section 1.2.1). If my account there is accepted, then a very interesting thing to be explained is the fact that a clear majority of chemists went over to Lavoisier’s point of view, despite the lack of convincing scientific reasons (what Kusch calls “narrow” reasons). Regardless of our

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differences rehearsed in the last section, I think Klein and Kusch would both accept this explanandum at least as a broad sketch. However, they both dispute the explanations I have offered. 3.2. Compositionism The explanation of an event as complex as the Chemical Revolution is bound to be multi-faceted, even if we focus on one particular aspect of it (as I am now doing). It is still not clear to me that I have reached a satisfactory explanation. Aside from accepting a limited role for the effectiveness of Lavoisier’s academic campaign for his own theory, I highlighted the rise of “compositionism” as an important background factor behind the consolidation of Lavoisier’s chemistry. Simply put, compositionism is a chemical system-type based on the assumption that there are immutable buildingblocks that make up chemical substances and that chemical reactions are mere re-arrangements of such building-blocks. The term “compositionism” is a light-touch coinage of my own, but the idea is not new and owes much to the work of various leading historians of science, Ursula Klein herself among them (Klein, 1994; Klein, 1996). However, Klein does not accept my proposal that the rise of compositionism was a significant background factor enabling the dominance of Lavoisier’s chemistry over phlogistonist chemistry, which I identified as an instantiation of “principlism”. Klein disputes that phlogiston theory was a good instantiation of principlism, and argues that even phlogiston theory was deeply compositionist. She points out that phlogiston was often regarded as a compositionist building block, amenable to the operations of decomposition and recomposition. Phlogiston even appeared in affinity tables by Geoffroy and others, which were the most emblematic representations of compositionist chemical practice. This is a far cry from the old hierarchical ontology in which different chemical substances have unequal status, which would be one of the requirements for a position that could be identified as principlist. All this is, of course, deeply related to her contention that there was no revolutionary change in the so-called Chemical Revolution: most chemists already had the compositionist ontology, and Lavoisier added or changed very little in that regard. I agree with Klein’s view here, but with some caveatsdand I think those caveats are sufficient to make room for what I was trying to say about the Chemical Revolution. Klein is absolutely right that compositionism was becoming so prevalent by the middle of the 18th century that even phlogistonist thinking was not free from it, but I think she overstates her case in the following respects. (1) Even though I would be the last person to deny that compositionism was clearly in the ascendant by the time of the Chemical Revolution, I think it would be a mistake to say that principlism was completely dead and all the phlogistonists had a “flat” ontology. At least Priestley’s thinking does seem to have been very principlist: for instance, he spoke of “air infected with animal respiration” or the transformation of air in a “regular gradation” by the addition of phlogiston (quoted in Chang, 2012b, p. 40). Whether or not this way of thinking was ultimately correct, it was very productive for him. Interestingly, it seems that Priestley’s thinking might have been more principlist than Stahl’s. It would be a very worthwhile research project to clarify Priestley’s metaphysical views and their roots precisely, building on the much-neglected work of John McEvoy (1978e79), for instance. For present purposes, it is sufficient to note that principlist thinking was alive and well in Priestley’s work, wherever he got it. Now, my view may be skewed because I have focused on Priestley rather than, say, Kirwan, whose thinking seems to have been more compositionist in being

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(2)

(3)

(4)

(5)

heavily concerned about not only weights but also affinity (see Mauskopf, 2002, and also Taylor, 2008). As noted in the last section, there were different versions of the phlogistonist system. And this may help to explain why Kirwan was able to give up phlogiston more easily than Priestley. Priestley was not alone. Many other phlogistonists also showed basic principlist tendencies: they did regard phlogiston as a different kind of entity from ordinary matter, and they had in mind a rather transparent mechanism of a principle imparting its characteristic properties to other substances. Klein points out that all chemists would have agreed that the properties of a compound would have been determined by the properties of its components. However, there are different ways in which this is done. A principle, such as phlogiston, gives the same characteristic property to many different substances that it combines with; for example, all calxes are rendered metallic by the injection of phlogiston. Other substances do not work like this; for example, there is no clear property that a wide array of lead compounds or zinc compounds share, and if there were, they would not have any clear link to the properties of lead or zinc itself. To render the example more phlogistonist, one could say: sulphur can only be sulphur because it is made up of both vitriolic acid and phlogiston, but the properties of vitriolic acid do not simply translate into properties of sulphur, nor do its compounds with various other chemicals share the same properties. This is one important way in which the typical phlogistonist ontology was not “flat”. The fact that most phlogistonists engaged in both compositionist and principlist thinking is something I have noted clearly in my work. What is more, I even suggested: “The Chemical Revolution may be seen as an internal collapse of the phlogistonist system[s] resulting from compositionist corruption.” (Chang, 2012b, p. 61). I have not developed that suggestion fully, but it is perhaps worth investigating further. That would be a task for another day, but I should briefly answer some questions Kusch considers unanswered (Kusch, 2015, in this issue, p. 78). First, “Since the phlogistonist system was itself moving ever closer to compositionist ideas, how could the compositionist trend lead to its destruction?” The answer is that phlogistonism could only accommodate so much compositionism without becoming incoherent. It was very difficult to adopt a flat ontology while maintaining any meaningful notion of a “principle”. Kusch’s other questions hinge on the observation that principlism was alive in Lavoisier’s own thinking; I was certainly not the first person to note this. Carlton Perrin went so far as to say that the entire first sub-group of Lavoisier’s table of simple substances were principles, and similarly Robert Siegfried called that set Lavoisier’s “taxonomic garbage” (see Chang, 2012b, p. 60). So one might wonder, if the uncomfortable mixture of principlism and compositionism contributed to the demise of the phlogistonist systems, why didn’t it do the same to Lavoisier’s system? Lavoisier did have his principlist aspects, too, but the tradition developed in such a way as to shed those, towards a more straightforward compositionism. This increased the coherence of the Lavoisierian system, while other advantages were lost (e.g., without caloric, Lavoisierian chemistry could no longer explain the emission of heat in combustion). Lavoisierian chemistry made the transition to the “Daltonian” phase only by ceasing to view caloric (and light) as a chemical substance, eventually getting rid of it altogether. My last remark raises the following question: couldn’t the phlogiston theory, too, have developed in a fully

compositionist way? The answer is that it certainly could have, and in the long retrospect that became possible by the early 20th century, it can be said to have developed in exactly such a way, in two different ways. Phlogiston may be identified with chemical potential energy, and energy is a rather compositionist concept in that it is a conserved quantity. Or phlogiston may be identified with electrons, and electrons make a very respectable compositionist substance. However, as it happened, faced with a very insistent and clear-cut version of compositionism employing weight-based chemical accounting, phlogistonists had no clear compositionist answer. In Cavendish’s early identification of inflammable air as phlogiston there was a compositionist promise, but that did not work out. And phlogistonists were not allowed the breathing space enjoyed by winners to work out their problems slowly and gradually.

3.3. Convenience Dismissing the rise of compositionism as a key to the explanation of Lavoisierian dominance, Klein turns to another set of factors (Klein, 2015, in this issue, p. 89). I entirely agree that these factors were important, and I can do so without giving up the significance of compositionist bias towards Lavoisier. Ease of teaching and communication was an important factor, as Klein point out. This is a social as well as intellectual reason; not much hangs on whether it should be classified as one or the other. I rather think of it as “convenience”, which is both intellectual and social. This convenience is what made the Lavoisierian campaign workable (after all, they did not have brute force at their disposal). Similarly, unity and systematicity were important factors. 3.4. Social explanations I have asked myself, and Martin Kusch himself, why it is so important for him to object to my account of the Chemical Revolution. If I understand correctly, it is because I seem to ignore, even dismiss, the importance of the sociological dimensions of the story. As a good sociologist, perhaps he cannot allow that a good account of any important event can be non-sociological. But Kusch’s position is not such a simple or superficial one; nor is mine. As he acknowledges, I did consider various sociological explanations of the Chemical Revolution. I rejected some of those explanations as unsupported, uninteresting, or limited in scope (explanations of allegiance by age, nationality, or immediate interests); I accepted some of them as important factors among others (the Lavoisierian campaign, as well as the reasons of convenience stressed by Klein, discussed above). But Kusch suspects that “Chang thinks that to explain a scientific belief or decision sociologically is to frame it as irrationally formed.” (Kusch, 2015, in this issue, p. 72). He thinks that I have neglected those social reasons that can be considered as good reasons. That is a very important point to consider, and it will bring us to the normative realm, which is the subject of the next section. But before we come to the question of the “goodness” of the reasons that Kusch highlights, let us consider how much explanatory work they do. Kusch makes much of the “experimenters’ regress” that he sees present in the Chemical Revolution. And I assume that he would want to argue that the regress was only broken through sociological mechanisms, though that is not absolutely required on the basis of what he says in his paper here (Kusch, 2015, in this issue, p. 76): “In the end, an Experimenters’ Regress is broken, and ‘closure’ is achieved, when a new distribution of trust is in place and stable, that is, when the scientific community is in broad agreement on who are the reliable spokespersons for the recently controversial area of science.”

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If my understanding is correct, for Kusch sociology is crucial in explaining how the agreement that allowed the consummation of the Chemical Revolution was possible. I think he is mistaken on both counts: the experimenters’ regress was not important here (which is not to say that it is not important in other situations), and to the extent it existed, it was broken due to reasons that are sociologically quite uninteresting. When I said that “there is nothing very sociological in Hufbauer’s account” (to be discussed momentarily), I spoke inaccurately. Everything humans do is sociological, just as it is physical and mental; but that is not an interesting observation. I have argued elsewhere (Chang, 2012a) that there was not much disagreements about the observed phenomena themselves in the Chemical Revolution, and I will not repeat that argument in detail. Kusch (2015, in this issue, p. 71) makes much of some initial disagreement that Lavoisier and Priestley had about experimental results. My general sense is that where there were disagreements about observed phenomena during the Chemical Revolution, they were resolved relatively quickly and without any particular fuss. The experimenters’ regress is simply not what fuelled the main line of debate in the Chemical Revolution. Against this contention of mine, Kusch highlights the case of the German controversy over the reduction of mercury calx, which is recounted in detail by Karl Hufbauer (1982). On the surface, this would seem like a perfect case to illustrate and support Kusch’s line. Around 1790 a group of German phlogistonists claimed that mercury calx, if fresh, did not give off oxygen when reduced by heat; conflicting experimental results were produced, and those who produced one result mistrusted those who produced a different result; it did not seem that there would be any way to resolve this difficulty. So how was agreement reached in the end? Kusch gives the following account (Kusch, 2015, in this issue, p. 77): “As Hufbauer sees it, ‘Hermbstaedt’s assault overwhelmed the phlogistic spokesmen’ (1982, p. 136). Although most of them initially attacked both Hermbstaedt’s experiments and his way of reportingde.g. his use of non-expert witnessesdtheir resistance quickly faltered over the next few months, as a wider public of chemists and scientists became convinced that Hermbstaedt had clinched the case.” As to why Hermbstaedt’s “assault” would have been “overwhelming”, Kusch highlights techniques of persuasion, such as witnessing, print communication, and an attempted exchange of materials with opponents. Reading that, I do not get a sense of overwhelming persuasion; I think “overwhelmed” here is a word that Hufbauer used ill-advisedly. What we hear in this part of Kusch’s paper (and the part of Hufbauer’s book that he draws from) just does not serve as a story showing that there were sufficiently good reasons for chemists to accept Lavoisier’s theory. Let’s read that passage from Hufbauer slightly more fully: “Hermbstaedt’s assault overwhelmed the phlogistic spokesmen. Each responded in his own way. Gren avoided direct comment. A conciliatory letter from J. B. van Mons suggested an easier line of retreat..” Gren, whom I listed as an eventual fence-sitter, is a very significant figure in this story, and an instructive case. Hufbauer (p. 137) goes on to explain what made Gren shift his position: “Months passed, then in October Gren learned that van Mons had an ingenious counterargument concerning the reduction experiment. At glowing heat, van Mons suggested, the red oxide of mercury quickly gave off much of its oxygen, turning into a blackish-red oxide of mercury. Hence, when this new compound was put into a pneumatic apparatus, it had little oxygen left to yield. Gren, seeing that van Mons’s suggestion reconciled the contradictory experimental results, readily embraced it. Soon he was writing his ally Westrumb to announce that he had abandoned his phlogistic system. He had been persuaded by van Mons that mercury calx was indeed a compound containing the base of vital air.” So we can see that, at least according to Hufbauer, what turned Gren was not

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Hermbstaedt’s “assault” itself, nor what other people around him thought, but a new cogent technical explanation of the experimental situation by van Mons. This is not a showcase of the sort of good social reasons that Kusch would want. It certainly does not fit Kusch’s gloss on the event: “the two sides could not agree on the correct experimental outcome since they could not agree on what would constitute a competent performance of the experiment.” (Kusch, 2015, in this issue, p. 77). They could, and did, agree on what was a competent experiment, and what its outcome was; the theoretical disagreement between Gren and Hermbstaedt continued beyond that agreement about the experiment. Nowhere does Kusch (or Hufbauer) demonstrate why Hermbstaedt and his advocates socially deserved to be trusted more than their opponents, and that seems to me a crucial missing plank in Kusch’s position. It seems to me that Gren acted like a good scientist, but there was nothing in those few months of 1793 that made van Mons a more trustworthy character, except that he came up with an ingenious new idea during that period. If we consider those who did go over to the Lavoisier side after Hermbstaedt’s campaign, there is a dilemma here for Kusch, at least as long as a more informative sociological account is missing: either they performed or witnessed Hermbstaedt-style experiments and by their own senses judged it to be correct, in which case they had a good reason but not one that is “social” in an interesting sense; or they believed the results because lots of other people did, in which case we have no evidence that they had a good reason (unless we know something quite detailed about the trustworthiness of the characters on opposing sides). Kusch admits that he has not given a full account of this episode, but deems himself to have given a “proof of concept”. But, so far, I think what we have is merely a statement of (twofold) faith: that there must have been social reasons, and they must have been good reasons. And whatever may be the case concerning the acceptance of experimental results, we also need to note the conceptual distance between an experiment and its theoretical interpretation. Recall that Priestley, Cavendish and most other British phlogistonists did not dispute the experimental results concerning the reduction of mercury calx by heat; indeed it was Priestley who performed that experiment and taught it to Lavoisier. But accepting the result of that experiment did not provide good enough reason to abandon the phlogistonist interpretation of this and other experiments, as Cavendish showed very calmly. The recognition that experiments needed interpretation was not missing in the German lands, either. Gren, too, provides a cogent illustration: even after accepting Hermbstaedt’s experimental result, he did not accept Lavoisier’s theory; rather, he adopted J. B. Richter’s “compromise theory”, which retained phlogiston while accepting Lavoisier’s weightfocused chemistry of oxygen. What Hufbauer (pp. 138e139) says about the other chief opponents of Hermbstaedt is interesting. Westrumb, whom I classified as a “die-hard”, also accepted Hermbstaedt’s result but did not give in to Lavoisier’s theory; instead, he “reverted to his old theory” that had some similarity to Cavendish’s latter-day interpretation. Hufbauer says that the other leading phlogistonist in this picture, Trommsdorff, stopped advocating phlogiston theory, but “retreated into empiricism” rather than converting to Lavoisierian theory. Curiously, by the start of the 19th century he appears as a dogmatic Lavoisierian arguing against Johann Ritter (see Chang, 2012b, p. 82); it would be interesting to learn what had got to him in the intervening years. 4. Do we like what happened? 4.1. Why get into the normative? I have made a clear normative claim about the Chemical Revolution: the phlogistonist system should not have been abandoned

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by scientists, because there were no good scientific reasons to do so. Making normative assessments of the past is something that the mainstream historians of science have come to avoid strenuously.3 I think Klein’s response here demonstrates that restraint in concrete practice. She will describe the event, she will explain why it happened, but she will stop carefully short of saying whether what happened is good. And I agree that a normative assessment is certainly not the only way to engage with the past, and that an excessive or clumsy deployment of the normative mode can interfere with some other essential aims of historiography. However, I think it is ultimately futile to try to remove ourselves and our own values from the histories that we write. Should we (and can we) be entirely free of value-judgment when we try to write about the rise of National Socialism, about the abolition of slavery, about the course of various epidemics, or even about the rise of McDonald’s? If not, why should that be different when we write about the achievements and the missed opportunities of science and the process of scientific knowledge-building? Many sociologists also want to steer clear of normative judgments. The Edinburgh brand of the sociology of scientific knowledge (SSK) gives a good instantiation of this attitude.4 Its impartiality principle demands equal attention to what is considered right/ wrong or good/bad, and this is most easily achieved by not getting into value-judgments at all. The causality principle demands that every occurrence (including someone holding a particular belief) should receive a causal explanation, which again tends to remove matters of normative assessment. So one can easily imagine a sociologist of knowledge simply being uninterested in whatever normative conclusions I might like to reach. But this is not Kusch’s attitude. He is intensely uncomfortable about my normative take on the Chemical Revolution, and his discomfort indicates something beyond mere disinterest. Either he feels that it is actually harmful to make normative conclusions, or he feels that I am making the wrong ones. I think it is the latter, as I will explore further below.

4.2. Phlogistonist propaganda? But let us get one other issue out of the way first. Kusch laments that I adopt “the English phlogistonists’ actors’ sociology” (or, their “propaganda”) (Kusch, 2015, in this issue, p. 73). I will readily admit that what I have written in my book is a “loser’s history”, bending over backwards to see if there isn’t some merit to what the phlogistonists believed. Kusch understands that I think I have performed a useful corrective service, against the backdrop of the secondary literature saturated with a triumphalist (not even Whiggish) celebration of Lavoisier.5 And it does not work to try to show me wrong here, as Kusch does, by citing back at me the very same secondary literature whose pro-Lavoisier bias I am trying to correct. Kusch’s “primer” on the Chemical Revolution (Section 3), ending dramatically with the admission of defeat by Kirwan in 1791, is strongly reflective of that bias, in its overall framing and in its various details. To counter its perpetuation, I can only recommend again using my own account as a corrective. Kusch (2015, in this issue, p. 74) says that “Chang insinuates a moral and intellectual superiority of the phlogistonists over and against the Lavoisians.” Rather than insinuating, I have said explicitly and clearly that I thought there were undesirable

3 See Michael Gordin’s (2014) essay review of my book for an extensive discussion of this issue in relation to my work especially on the Chemical Revolution. 4 Bloor (1991, chap. 1), remains the clearest statement of this program. 5 On the prevalence of triumphalism concerning Lavoisier, see Chang (2009) and references therein, including Bernadette Bensaude-Vincent’s studies of French nationalistic celebration of Lavoisier.

character traits on the Lavoisierian side. Intellectually, too, I gave a lengthy and systematic assessment of the merits of both sides (Chang, 2012b, pp. 19e29). In that section I hope I pull back sufficiently from the admittedly biased corrective rhetoric seen earlier in the chapter. But if in the end I align myself with what Kusch perceives as phlogistonist propaganda, that is because my own study of the primary sources gave me the conclusion that the perception of the situation by the best of the phlogistonists had merit and justice on their side. Perhaps what is offensive to Kusch here is that I do not respect the impartiality principle of SSK. Given that my work is not a piece of SSK, I do not see why I would have to follow that principle and renounce my own value-judgments, as long as they are carefully made and justified. 4.3. Good social reasons The main line of attack Kusch takes on my normative position is to say that there were good reasons for the Chemical Revolution, while he rejects my explanation referring to the advent of compositionism. The reasons he prefers are social ones. Kusch (2015, in this issue, p. 76) says that there were “overwhelmingly good” reasons (as scientific as any other), aside from experimental and theoretical considerations, to favour Lavoisier’s position. Here we see a manifestation of the classic ambiguity of “good.” To say that “we can understand the social factors that caused this social phenomenon” is a different thing altogether from saying that “we think these people behaved the way they did for commendable reasons”. I take it that Kusch intends both senses of “good” here. What are these good reasons? He explains: “such ‘indirect’ reasons concerned markers of trustworthiness in chemical matters: track records, social indicators of reliability, institutional status, standing in the profession, plausibility of vision for the field of chemistry as a whole, . and much else besides.” I despair about that list, thinking about how it could be rendered neither a matter of “mob psychology”, nor something question-beggingly circular (especially track record), even though Kusch stresses that these reasons were “closely intertwined” with what he calls “narrow” reasons, not to be separated out and dismissed. Even adopting Kusch’s framework for the sake of argument, I just do not think sufficient argument has been given for providing “proof of concept”. This point is related to my dissatisfaction, discussed above, with Kusch’s treatment of Hufbauer’s discussion of the German debate. What was it that made Lavoisier and his allies and advocates in various countries so trustworthy? According to the social markers listed by Kusch above, why should Lavoisier, especially to British people, have seemed more trustworthy (scientifically, and more generally) than the impeccably aristocratic Cavendish, or the very powerful and well-connected Joseph Banks (who had a decidedly low opinion of “French chemistry”)? Perhaps the radical dissenter Priestley was less trustworthy to most people than Lavoisierdbut then, why did Lavoisier remain more trustworthy in Revolutionary France after he was, with good reason, branded an enemy of the people and executed, compared to Priestley, whose demise in his own country was precisely for his support for the French Revolution? And when it comes to further developments of chemistry in the Lavoisierian tradition, why should anyone have trusted poor John Dalton, who was without money, social standing, political power, academic degrees, or positions of scholarly influence? The answer, I think, will be at least complicated. 4.4. The individual vs. the social Let me now come to what I think is at the root of our disagreement. It is not the case that I operate on the equation of

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“social ¼ irrational”. It is also not the case that I am simply uninformed about sociology. I do not claim to be an expert in sociology, but I have enough awareness about it, the sort of thing that Harry Collins would call “interactional expertise”. And even though I have not encountered or worked out for myself a kind of sociological account of knowledge-building that I find satisfactory, that does not mean that I deny that scientific knowledge arises from socially based practices. I have actually been working on finding or crafting a sociological framework I would find more useful, with guidance from Martin Kusch himself. What I find troublesome in the currently available form of SSK and related doctrines is not that it shrinks from the normative, but that it in fact presupposes a kind of normativity that I find objectionable. (What I am going to say now is speculative, and I offer it to Kusch as something he can examine and critique.) The normativity I refer to is usually well-hidden, but in studying Kusch’s critique of my position I have come to recognize it more clearly. Now, I think some sociologists are social determinists, in a purely causal and not normative way: such-and-such social forces determine how each individual behaves, and the individual simply has no choice about it, whatever delusions of free will and selfdetermination she or he might entertain. I suspect that Kusch, and many other sociologists of knowledge, are not such social determinists. But I have been unclear on what their position in this regard is. I now think it is an unspoken normativism: an individual ought to behave in a way that our best theories of social dynamics dictate, thereby following good social reasons. An individual who offers resistance to the standard social forces would actually be regarded as irrational, in the sense of behaving incomprehensively. So, 18th-century chemists ought to have followed Lavoisier because there were good social reasons to do so; it is good that most of them did, and it is egregious of me to suggest that they ought not to have. In contrast, I want a kind of social account of knowledge (and of life in general) in which the individual’s independence, judgment or dissent is not written out by the very conceptual structure and commitments of the analytical framework we adopt. I seek the kind of sociology in which the full dialectic between the collective and the individual can be expressed and investigated. Kusch has the opposite worry, that too much stress on the individual’s independent thinking and decisions would blind us to the social structures and forces that are actually so important in the constitution and the flourishing of the individual. In our discussions in person, it has emerged that this contrast in our approaches seems linked to our respective upbringing. I grew up in a military dictatorship (which South Korea was, throughout my period of growing up there), in which it was a most important struggle to claim the individual’s right to think and act independently. Kusch grew up in a much freer West Germany, where the individualist dissolution of civil society seemed the much more present threat. So here is a sociological explanation of our difference! But someone else growing up in our respective situations could have had very different reactions. For a full explanation, we will need to take into account both the external factors imposed on the individual and the individual’s own free determinationdI think Kusch will agree with me on this point. 4.5. Sociology, pluralism and the Chemical Revolution Let me conclude by returning to the issue of pluralism. Kusch is clearly concerned that the story of the Chemical Revolution should not be used to bolster the kind of pluralism I advocate. Whether this is because he doesn’t like my pluralism, or because he simply doesn’t think that the case supports my general doctrine, or both,

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I’m not entirely sure. I hope to have a clarification on that question, perhaps at another opportunity. I look forward to discussing his view on pluralism, especially in relation to relativism, which he is clearly in favour of. I think he and I are agreed (unlike many other commentators) that pluralism and relativism are two very different things. To put it crudely, I am for pluralism and against relativism. What is Kusch’s position? On my own side, I welcome this opportunity to clarify exactly what the Chemical Revolution story does in my argument for pluralism. It may be better to start by confirming what I am not saying. First of all, I am not saying that if the state of chemistry in the Chemical Revolution (or any other specific phase of scientific development) was pluralistic, that constitutes an argument for normative pluralism.6 Normative pluralism applies whatever the descriptive situation, and it is not directly affected by the descriptive situation: if scientists have been extremely monist, normative pluralism will say they should have been more pluralist; if scientists have been quite pluralist, normative pluralism will say “well done” to that. It should be plain that a descriptive thesis, by itself, cannot prove normative theses. I also do not claim that a general normative pluralism directly follows from the view we take about one episode. Even if pluralism worked out (or would have worked out) well in one case, that cannot prove the general benefit of pluralism. My Chemical Revolution story is simply an illustration of the possibility and potential of pluralism in science. In my book (Chang, 2012b), the general arguments for pluralism are given in Chapter 5, quite independently of the ins and outs of the Chemical Revolution story in Chapter 1, though with references back to it. With those possible mis-directed concerns out of the way, let me focus on what I think Kusch is actually getting at. He seems to be objecting to a very specific inference I draw concerning the Chemical Revolution: if there weren’t good scientific reasons to abandon the phlogiston theory, then scientists shouldn’t have abandoned it. One key argument from Kusch is “conditional” (Kusch, 2015, in this issue, p. 76): “I want to show that even if we grant Chang the mentioned underdetermination, his prescriptive scientific pluralism does not follow.” What he means the underdetermination here is this (in his words): “neither experimental results nor theoretical considerations available to chemists at the time were sufficiently strong to rationally compel abandoning the phlogiston theory”. This is where his “good social reasons”, discussed in the last section, come in. And aside from his preference for Lavoisier, Kusch’s presumption seems to be that good social reasons should tend toward monism, and I am not sure how that idea can be justified. My position is that since the phlogistonist and the oxygenist systems each had its merits and promises, chemists should have cultivated both of them. I do not see why a commitment to social explanations should somehow translate into a normative monism. And my puzzle here is related to another point of incomprehension that I have, which is where Kusch says (2015, in this issue, p. 72): “Linking Chang’s rejection of sociological explanations to his case for pluralism is not straightforward.” Of course it wouldn’t be straightforwarddthere is no link here to be made! What matters for my normative pluralist assessment is the judgment that there weren’t sufficiently good scientific reasons to preserve one system but not the other. If that is the case, then I am going to lament any kinds of cause (social or not) that prevented the flourishing of both systemsdwhether it be undue

6 So it is not cogent for Kusch to argue (2015, in this issue, p. 75): “As it stands, Chang’s chart does not make a case for prescriptive pluralism.” It was never meant to do that.

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social pressure, a mass delusion, a widespread lazy psychological habit, or a freak meteor that wiped out the world phlogistonist convention. The same puzzle continues when I read Kusch’s concluding sentence (2015, in this issue, p. 78): “I hope to have made plausible that a sociological approach to the Chemical Revolution is not ruled out by Chang’s theoretical considerations or his historical data.” Ruling out a sociological approach was not something I had in mind as an aim of my work. As explained above, the only negative thing I have found and expressed about sociology is that I do not find the Chemical Revolution easily explained by the standard sort of sociological factors that have been invoked in the extant literature. That does not mean sociology cannot do better than that. Having said all that, what can I say about the implications of the Chemical Revolution story (as I tell it) for general normative pluralism? After all, I made the provocative statement that “I became a pluralist because I could not honestly convince myself that the phlogiston theory was simply wrongdor even genuinely inferior to Lavoisier’s oxygen-based chemical theory”, though I immediately qualified that statement (Chang, 2012b, p. 253). It is of course true that a striking episode serves as an inspiration, and as some measure of support, for a general position. So, if one wishes to reject normative pluralism in general, it would be in one’s interest to dispute my normative claim about the Chemical Revolution and some other similar striking episodes that I have studied. And in this context, descriptive pluralism can also have a normative implication: if the particular practices we are examining are seen to have been pluralistic yet effective and progressive (as is the case in the stories told in Chapters 2 and 3 of my book), then it does constitute evidence against the kind of normative monist position which declares that only monistic science is good science.

References Bloor, D. (1991). Knowledge and social imagery (2nd ed.). Chicago: University of Chicago Press. Chang, H. (2009). We have never been whiggish (about phlogiston). Centaurus, 51, 239-264. Chang, H. (2010a). [Review of] “Ursula Klein and Wolfgang Lefèvre, Materials in eighteenth-century science: A historical ontology”, 1650e1850: Ideas, Aesthetics, and Inquiries in the Early Modern Era, 17, 380-384. Chang, H. (2010b). The hidden history of phlogiston: How philosophical failure can generate historiographical refinement. HYLE: International Journal for Philosophy of Chemistry, 16(2), 47-79. Chang, H. (2011). Compositionism as a dominant way of knowing in modern chemistry. History of Science, 49, 247-268. Chang, H. (2012a). Incommensurability: Revisiting the Chemical Revolution. In V. Kindi, & T. Arabatzis (Eds.), Kuhn’s The structure of scientific revolutions revisited (pp. 153-176). London: Routledge. Chang, H. (2012b). Is water H2O? Evidence, pluralism and realism. Dordrecht: Springer. Gordin, M. D. (2014). The Tory interpretation of history (review of H. Chang, Is water H2O?) Historical Studies in the Natural Sciences, 44, 413-423 Hoyningen-Huene, P. (2008). Thomas Kuhn and the Chemical Revolution. Foundations of Chemistry, 10, 101-115. Hufbauer, K. (1982). The formation of the German chemical community (1720e1795). Berkeley and Los Angeles: University of California Press. Klein, U. (1994). Origin of the concept of chemical compound. Science in Context, 7(2), 163-204. Klein, U. (1996). The chemical workshop tradition and the experimental practice: Discontinuities within continuities. Science in Context, 9(3), 251-287. Klein, U., & Lefèvre, W. (2007). Materials in eighteenth-century science: A historical ontology. Cambridge, Mass.: The MIT Press. Klein, U. (2015). A Revolution that never happened. Studies in History and Philosophy of Science, 49, 80-90. Kusch, M. (2015). Scientific pluralism and the Chemical Revolution. Studies in History and Philosophy of Science, 49, 69-79. Mauskopf, S. H. (2002). Richard Kirwan’s phlogistic theory: Its success and fate. Ambix, 49, 185-205. McEvoy, J. G. (1978e79). Joseph Priestley, ‘aerial philosopher’: Metaphysics and methodology in Priestley’s chemical thought, from 1772 to 1781. Ambix, 25 (1978): 1-55, 93-116, 153-175; 26 (1979), 16-38. Taylor, G. (2008). Tracing influence in small steps: Richard Kirwan’s quantified affinity theory. Ambix, 55, 209-231.

The Chemical Revolution revisited.

I respond to the critical comments by Martin Kusch and Ursula Klein on my account of the Chemical Revolution. I comment along three different lines: d...
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