Who Owns the Twentieth Century? (And Is It Worth Owning)

Previous articleNext article FreeWho Owns the Twentieth Century? (And Is It Worth Owning?) Stephen G. Brush. With Ariel Segal. Making Twentieth Century Science: How Theories Became Knowledge. vxii + 531 pp., bibl., index. New York: Oxford University Press, 2015. £25.99 (cloth). Jon Agar. Science in the Twentieth Century and Beyond. ix + 614 pp., index. Cambridge: John Wiley & Sons, 2012. £30 (cloth).Joseph D. MartinJoseph D. Martin Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreThe twentieth century enjoys a firm grip on our profession. Well over half the research articles published in this journal since 2000 devote significant attention to the period between the 1890s and the 1990s.1 Similar trends prevail in other leading publications. But this outpouring of scholarship alone does not create a collective sense of how historians of science should confront the twentieth century as an epoch. The synthetic reflection that established the scientific revolution as a historiographical category and lent the nineteenth century a sense of cohesion remains to be undertaken for the twentieth.2A panoramic outlook on more recent historical eras is a pressing necessity. Publishing trends suggest that we will confront future methodological questions and navigate our evolving professional identity largely on twentieth-century turf. What, then, defines twentieth-century science? In some ways, this question is naive, even trivial: it surprises no one that the currents of history disdain our thin calendrical embankments. But centuries, decades, and other conventional durations often prove useful for collating practices that shared a family resemblance and naming periods about which we might claim that continuity prevailed over discontinuity. Can the twentieth century offer such utility? The books under review can each be read as an attempt to use the twentieth century in that way and, in so doing, to claim it for a particular vision of how the history of science should be done.Stephen Brush’s Making Twentieth Century Science: How Theories Became Knowledge is both an extended argument that scientists value explanatory power over novel prediction when choosing which theories to accept and a plea for careful attention to the content of science in writing its history. Jon Agar, in Science in the Twentieth Century and Beyond, details how science connects to “working worlds,” the social, cultural, political, and technological arenas that bind science to essentially human problems. If this recalls the split, often considered stale, between internal and external, conceptual and contextual, approaches to the history of science, it is no accident. For all our efforts to transcend this distinction—if these works are any guide—it still holds considerable sway over our practice. Apart from their many intrinsic merits, these books present an opportunity to assess how that methodological legacy shapes understanding of the time period that now predominates in the history of science and to ask what the definitive stories of that era should be. They suggest, I argue, that we still lack a cohesive picture of twentieth-century science and, furthermore, that we can expect it to remain elusive.A Century of Theory ChoiceStephen Brush’s Making Twentieth Century Science confronts one clear question: Why have scientists accepted theories? Notwithstanding numerous reception studies of relativity, quantum mechanics, and Darwinism, Brush finds that historians and philosophers neglect this question. Historians, he charges, focus on the genesis of theories, or on the circumstances of their acceptance, without interrogating scientists’ rationales for accepting them. Philosophers are too preoccupied with the question of why scientists should accept theories to examine how they actually do. Brush considers four potential explanations of how a new theory wins scientists’ allegiance: it might anticipate hitherto unknown facts (novel prediction); it might provide a compelling account of previously known facts (explanatory power); it might be more beautiful than its competitors (aesthetics); or it might be favored by social, cultural, or professional factors (social construction). The bulk of the book presents, with scrupulous care, a series of case studies that test these candidate explanations.Before exploring these examples, Brush issues a brisk dismissal of social construction in Part 1. He does credit social constructionists for undercutting whiggishness, promoting a much-needed emphasis on scientific practice, and exposing some genuine ideological biases. He finds them open to criticism and their work quite fun to read. But Brush’s prevailing sentiment is that social constructionist claims are rarely supported by hard evidence and that the approach’s roots in 1970s counterculture opposition to Cold War technocracy make it ill-suited to a context in which antievolutionism and climate change denial, rather than the Strategic Defense Initiative and Agent Orange, dominate public scientific controversy. To understand why scientists accept theories, he contends, we need to inspect the documentary record individual scientists leave, and most of the time it shows that social factors play but a small and limited role.With social construction shunted aside, Brush turns to the bugbear that bothers him more: novel prediction. The notion that theories are either more likely to be adopted, or more worthy of adoption, when they predict facts not yet known is an old philosophy of science standby.3 It makes intuitive sense. What is surprising about a theory assembled from available evidence explaining facts we already know? The real question, the argument goes, is how a theory’s untested implications stand up to experimental scrutiny. But Brush, eyeing the documentary record, is skeptical that this surface-level plausibility tells us much about how theories actually won scientists over. The book’s three remaining parts scrutinize the physics and chemistry of atoms and molecules, the physics of space and time, and evolutionary biology, respectively. Brush concludes that scientists buy theories for their explanatory power; novel prediction comes as lagniappe.Brush’s treatment of the general theory of relativity (GTR) reflects his general pattern of argument. GTR is often presented as the exemplar of a theory established by predictive success. Arthur Eddington’s photographic plates of the 1919 solar eclipse validated the novel prediction about the degree to which the sun’s gravitational field bends passing starlight and cemented GTR’s superiority to Newtonian mechanics—or so the story goes.The confirmation of GTR’s light-bending prediction was psychologically powerful, made news worldwide, and transformed Albert Einstein into a celebrity.4 But the fact that a prediction captured the popular imagination reveals little about why physicists accepted GTR. Brush asks how physicists weighted light bending vis-à-vis other evidence and how much of that weight derived from the theory anticipating a previously unknown fact. From physicists’ and astronomers’ published statements, he concludes that although light bending counted in GTR’s favor, it was no more important than other available evidence—and many thought it less so. The theory’s explanation of existing anomalies—the forty-three seconds of arc per century difference between Newtonian calculations of Mercury’s perihelion advance and observed values, Michelson and Morley’s null result, the redshift of spectral lines—often counted for more.In fact, Brush argues, it is rational that explanation of existing anomalies should attract scientists’ theoretical allegiances more strongly because the scientific community has already tried, and failed, to account for them. Novel predictions have not endured rigorous scrutiny. A good skeptic should remain receptive to a better explanation. In an extensive survey of physicists’ writings from the 1920s, Brush finds only one who claimed that light bending provided better evidence for GTR because it was a novel prediction. The majority praised the theory for explaining known phenomena and doing so beautifully. Success accommodating existing evidence emerges as scientists’ principal motive for theory choice in most of Brush’s examples. The elegance with which it does so often plays a supporting role. Novel prediction rarely, according to Brush’s analysis, holds special status. Successes like the prediction of new elements from the periodic law draw disproportionate attention; but they are the exception, not the rule. And only in rare and aberrant cases, such as Lysenkoism in the Soviet Union, do social factors serve as primary motivators of theory choice.The examples that establish this pattern cover a noteworthy range, especially considering the depth in which Brush reconstructs conceptual developments. They include Dmitri Mendeleev’s periodic law and August Kekulé’s theory of benzene’s structure, natural selection and molecular genetics, and quantum mechanics and big bang cosmology. Each case mobilizes some mixture of textbooks, which show when a theory enters the canon; review articles, which often explain why a theory is useful; research articles, which, with simple quantitative methods, can reveal what proportion of scientists are using a theory at a given time; scientists’ popular writings, which sometimes argue for accepting theories more directly than research publications; and prize citations, which track the prestige associated with theoretical accomplishments. These sources prove apt for answering the question of when and why individual scientists accepted a theory. They nevertheless leave some questions. I will address two: what it means to accept a theory; and the difference between individuals accepting a theory and a community reaching a consensus.Brush makes a telling observation about declining interest in GTR after the 1920s: “there were no new convincing tests of the theory’s predictions until the development of better technology and advances in atomic physics. ... In the meantime, quantum mechanics offered many more research opportunities for physicists” (p. 350). This suggests another reason researchers might adopt a theory: it gives them something to do. C. Kenneth Waters distinguishes between a theory’s explanatory scope and its investigative reach.5 Brush emphasizes the former, but his analysis hints that investigative reach—the range of problems a theory allows scientists to explore—also influences theory choice.Quantum theory (Ch. 8) is one example. The old quantum theory, represented by the Bohr model of the atom, was “not considered really satisfactory” (pp. 220–221) and “was never fully accepted before it was replaced by quantum mechanics” (p. 488). Even so, it inspired copious publications from 1913 until 1926, when quantum mechanics offered a more satisfying alternative. Physicists might have considered the Bohr atom crude, but they needed a tool to hack through the jungle of spectroscopic data generated by new instruments and experimental techniques. Similarly, many scientists rejected the metaphysical implications of quantum mechanics even as they published work that used the theory, thus accepting it by the standard Brush himself often adopts.Brush skirts the slippery question of when we can say that a scientist has accepted a theory, but it does not bear centrally on his case against novel prediction. Rather, it shows how his argument could have been sharpened by engaging with more recent philosophy of science. Brush reprimands philosophers for making ahistorical claims about the potency of novel prediction. But the philosophical picture of scientific reasoning he attacks most forcefully is the hypothetico-deductive method, which is principally of historical interest for many philosophers. He praises social constructionists for highlighting scientific practice but neglects a similar practical turn in philosophy, attention to which might have allowed him to build a more powerful case that his approach can be useful for philosophers. An agenda proposing “systematic study of scientific practice that does not dispense with concerns about truth and rationality,” as advocated by the Society for Philosophy of Science in Practice, accords closely with Brush’s mission.6The second question concerns the difference between acceptance and consensus. Brush documents how individuals adopted theories. It is one thing to show that individuals—even a substantial group of important individuals—have accepted a theory but quite another to demonstrate that theory’s consensus status. The latter requires that the theory is no longer competing against other serious alternatives.7 If scientists provisionally accept a theory because of its explanatory power, beauty, or investigative reach, might novel predictions, which take time to validate, help shut down alternatives and crystallize a consensus? What is the fate of theories that fail to produce novel predictions? Take string theory. Although lively and fashionable for over forty years, none of its predictions has proved testable, let alone been tested. This suggests the historical analogue of a gene knockout experiment: asking what happens in novel prediction’s absence might reveal something of its function.Wanting for predictive success, string theorists turn to explanatory power and aesthetics. They seek to explain the large and powerful data set telling us that the elements of the standard model of particle physics have the values they have and to resolve the persistent incompatibility between relativity and quantum mechanics. John Horgan crisply summarizes the string theorist Edward Witten’s defense of aesthetic power as the claim that string theory is “too beautiful to be wrong.”8The cumulative effects of four decades without an experimentally validated prediction, however, are weighing on string theory. It has suffered vigorous attack from philosophers and other physicists who cite its predictive failure as cause to reject it.9 Explanatory power and elegance, even within favorable social conditions (in the 1980s and 1990s, some of the most high-profile physics departments became dominated by string theorists), have not secured consensus for string theory. Novel prediction might rarely be a primary motive for individuals to accept theories, but it does appear that its absence can inhibit consensus, indicating that it might have more import for communities than Brush allows it for individuals.The above considerations do not detract from the remarkable achievement this book represents. Brush commands the technical details of a wide range of sciences and musters an impressive array of sources to answer a clear question convincingly and with only very few minor factual slips. The book’s typographical errors, in contrast, are numerous. Oxford University Press has apparently done only cursory copyediting, leaving the text riddled with extra or missing spaces, misplaced punctuation, and, on occasion, typesetting errors that obscure the author’s meaning. The confusion of “l” and “1” in Brush’s discussion of the Pauli exclusion principle, for instance, leads to the absurdity “1 may be either 0 or 1” (p. 229). Such slipshod production is surprising from a press so esteemed as Oxford, whose authors deserve better.Production aside, the book is a monument to scrupulous scholarship. As such, it advances an implicit argument about what it means to do the history of twentieth-century science. The twentieth century as a category, in fact, plays almost no role in Brush’s exposition beyond the book’s title. The bulk of the discussion concerns the period between the 1860s and the 1930s, with a few brief sorties into the Cold War. It offers scant defense of the twentieth century as a useful historiographical category. It does offer a vision of the history of science as responsible for the content of science, which allows us to ask questions that fall unambiguously and nearly uniquely within its remit and answer them by substantiating clear, causal historical explanations. It is a field with a distinct identity. Like the best of the theories Brush discusses, it gives researchers an unmistakable mission.Working with Working WorldsWhereas Brush pays little heed to the twentieth century’s temporal boundaries, Jon Agar addresses them explicitly in Science in the Twentieth Century and Beyond. The book’s motivating conceit is to follow forward the threads that pass through a temporal plane drawn at 1900. These include many of the topics Brush addresses: molecular structure, relativity and quantum mechanics, and evolutionary biology. But Agar ventures beyond the best-known stories from the physical and biological sciences. Breadth is the book’s great strength. Alongside familiar accounts of chemistry, physics, and biology, it engages psychology, the social sciences, geology, operations research, virology, and other fields that might seem unjustly peripheral when placed beside more dominant narratives. In this epic work of synthesis, Agar makes a strong case that their stories are just as representative of twentieth-century science as the better-known narratives of more visible fields.The topical range Agar covers compounds the challenge of identifying a theme that can braid a sturdy narrative from the threads he follows across such a span of time. Agar settles on “working worlds,” which he defines as “arenas of human projects that generate problems” (p. 3). Working worlds are the realms of human activity we find when we ask whose interests science serves and why. The book unfolds roughly chronologically, articulating its examples in terms of some of the key working worlds science served throughout the twentieth century, most prominently those of agriculture, warfare, commerce, and medicine.Agar begins by noting that the early 1900s witnessed foment in the physical, life, and human sciences and so is a useful starting point. Part 1, after introducing the working worlds framework, traces the development of quantum theory and relativity, experimental genetics, and psychology and immunology, which aspired to emulate the successes of physics and biology. In each case, Agar emphasizes what might be called “external” factors. The new physics both sprang from and contributed to global communication and transportation networks. Genetics was of special interest to the agriculturalists tasked with feeding ballooning populations. The sciences of the mind were put to work classifying those populations, sorting schoolchildren and soldiers into categories validated by a battery of new psychological tests. When Agar sees politics, technology, and ideology, however, he does not see external forces buffeting science from without but, rather, integral components of its function. Working worlds are features of science, not bugs.Part 2 addresses World War I and its aftermath. Wartime demands forged strong ties between government, industry, and academia, raising the stock of physics and chemistry as they showed how their expertise could advance practical ends. Following the war, science responded to the instability of the Weimar Republic in Germany (Ch. 6), hastened industrialization in the United States (Ch. 7), and with the and demands of the United global (Ch. Agar suggests that the development of biology, both in the Soviet and scientists with (Ch. He traces how science in both and not (Ch. He considers the of big science in the period and the and technological circumstances that made it (Ch. with Brush’s approach should be Brush at that the evolutionary was a of Brush’s analysis of why accepted natural selection on how numerous of evidence key individuals that not or best the available He in the series of the principal of the often in that theoretical from the through Agar, however, that we understand the to be just the and reception of we something very (p. we the working of and a The difference is not one of simple it is a about the of and evidence that are when we historical difference is in these of Brush emphasizes the rational scientists used to to accept the theory, as through their Agar turns to of technological The that the of and the that it a with working worlds But the weight we should actually on factors when their to the genesis and of relativity is a question himself holds at If forces do theory genesis and they are often forces so as historians like Brush are They might in a but documentary evidence that can demonstrate their is Part World War and the Cold focus remains on the of historical that rarely appear in scientists’ The working worlds theme leads him to the many historians have as definitive of World War The of science to is a Although the represented science on a new it from between science and forged World War I and on big science in the Similarly, on in and to the working of Cold War and similar between science and early twentieth-century account of the scientific that after World War into Part on the science of examples in these are brief and to working worlds less and to a of examples, all but for on the on against research, scientific between social and the and the War. This and other although sometimes are as they historiographical that rarely into four of twentieth-century science. The is the of working those of is the of scientific power from to the United is the that these trends should not the missing theories, the and science under the of all I and physics, science, and evolutionary as narratives largely from and most that might yet prominently in the twentieth-century Agar the of from the physical sciences in the early twentieth century to the sciences in its decades as his he technology particle physics of the without large research, and climate science as threads that a of science might to follow reflects his that future historians might of the century in similar to how he has the between the working worlds of

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