Why Trust Science?

by Naomi Oreskes

  The argument of this book is that the answer to our question—Why Trust Science?—is not that scientists follow a magic formula (“the scientific method”) that guarantees results. That idea persists in textbooks and the popular imagination, but it does not stand up to historical scrutiny. What does stand up is a portrait of science as a communal activity of experts, who use diverse methods to gather empirical evidence, and critically vet claims deriving from it.

  The diverse methods of science have identifiable common elements. One is experience and observation of the natural world; another is the collective critical scrutiny of claims based on those experiences and observations. In chapter 1 we developed the argument that the appropriate basis for lay trust in science is the sustained engagement of scientists with the natural world, coupled with the social character of science that includes procedures for critical interrogation of claims.

  All social arrangements rely on trust, and many involve expertise, be it from doctors, dentists, plumbers, electricians, car mechanics, accountants, auditors, tax attorneys, real estate appraisers, or what-have-you. Even buying a pair of shoes may rely on trusting the salesman to measure our feet properly. If trust in experts were to come to a halt, society would come to a halt, too. Scientists are our experts in studying the natural world and sorting out complex issues that arise in it. Like all experts, they make mistakes, but they have knowledge and skills that make them useful to the rest of us. The crucial component that separates science (and here I include the social as well as the natural sciences) from, for example, plumbing, is the centrality of the social vetting of claims.

  The critical scrutiny of scientific claims is not done individually; it is done collectively, in communities of highly trained, credentialed experts, and through dedicated institutions such as peer-reviewed professional journals, specialist workshops, the annual meetings of scientific societies, and scientific assessments for policy purposes.6 A crucial aspect of this process is revision: most peer-reviewed papers are revised many times prior to publication, both informally as preliminary results are presented at conferences and workshops and drafts are sent to colleagues for comment, and then formally through editorial peer review. Papers are then revised in response to reviewers’ suggestions of clarifications and corrections. If errors are detected after publication, journals may issue errata or retractions. (In this regard, retractions should be seen as essentially a good thing.) This process of critical scrutiny and revision is what philosopher Helen Longino has called “transformative interrogation,” what anthropologist Bruno Latour calls the “agonistic field.” It is the process by which, as historian Martin Rudwick has stressed, novel solutions to problems are developed, accepted, and sustained as facts.7

  Exchanges among scientists at times get testy, but this is to be expected when hard-won intellectual accomplishments are called into question. The fact of contestation—even highly emotional contestation—is not by itself evidence that anything is wrong. (On the contrary, it may be a sign that things are right, as scientists are taking a challenge seriously and neither ignoring nor dismissing it.) Through this process of contestation, novel claims come to be intersubjectively accepted and ultimately viewed as objectively true. The social aspect of scientific work is thus crucial to the question of whether or not scientific conclusions are warranted, because it helps to ensure that conclusions are not merely the opinions of individuals or dominant groups, but something less personal and more reliable. A claim that has survived critical scrutiny becomes established fact, and collectively the body of established facts constitute scientific knowledge.

  The beauty of this picture is that we can now explain what might otherwise appear paradoxical: that scientific investigations produce both novelty and stability. New observations, ideas, interpretations, and attempts to reconcile competing claims introduce novelty; critical scrutiny leads to collective decisions about what obtains in the world and hence to stability of knowledge claims. This picture also helps us to appreciate the irony that what was once viewed as an attack on science—the articulation of its social character—provides the basis of the strongest defense we can make of it.8

  That said, those of us who wish to defend science from ideologically and economically interested attack must be not only willing and able to explain the basis of our trust in science, but also to understand and articulate its limits. This means coming clean about the various ways in which things can go wrong. In chapter 2, we explored a number of instances where scientists, in hindsight, did get things wrong. Here, we saw the salience of three matters especially: 1) consensus, 2) diversity, and 3) methodological openness and flexibility.

  Consensus is essential to our argument for the simple reason that we have no way to know for sure if any particular scientific claim is true. As philosophers going back to Plato (and perhaps before) have long recognized, we do not have independent, unmediated access to reality and therefore have no independent, unmediated means to judge the truth content of scientific claims. We can never be entirely positive. Expert consensus serves as a proxy. We cannot know if scientists have settled on the truth, but we can know if they have settled. In some cases where it is alleged in hindsight that scientists “got it wrong,” we find on closer examination that there was, in fact, no consensus among scientists on the matter at hand. Eugenics is a case in point.

  Diversity is crucial because, ceteris paribus, it increases the odds that any particular claim has been examined from many angles and potential shortcomings revealed. Homogenous groups often fail to recognize their shared biases. In chapter 2, we saw not only how the Limited Energy Theory instantiated prevailing late nineteenth-century American gender bias, but also how Dr. Mary Putnam Jacobi shone a light on those biases and in doing so revealed serious flaws in both the theory and its evidentiary basis. We also saw how socialist geneticists were particularly articulate in their opposition to eugenics, drawing on their politics to question the obvious class bias in many eugenic theories and proposals. One did not have to be a socialist to question eugenics, but socialist class consciousness played a role in a substantial line of dissent.

  Methodological openness and flexibility are necessary because when scientists become rigid about method, they may miss, discount, or reject theories and data that do not meet their standards. We saw this at play in the history of continental drift theory, as American scientists rejected a theory that did not follow their preferred inductive approach; in the history of the contraceptive pill, where gynecologists rejected case reports from patients because they were viewed as subjective and therefore unreliable; and in the evaluation of dental floss, where double-blind trials were simply not possible.

  These insights make clear that we are not powerless to judge contemporary scientific claims. We can ask: Is there a consensus? Is the community undertaking the studies diverse, both demographically and intellectually? Have they considered the issue from a variety of perspectives? Have they been open to diverse methodological approaches? And have they paid attention to all the relevant evidence, not missing or discounting some substantial portion of it? Have they avoided becoming fetishistic about method?

  In closing, let’s consider one more topic: sunscreen. It is well known that some widely used ingredients in sunscreens—particularly oxybenzone—may disrupt endocrine function in laboratory animals.9 Oxybenzone is also is toxic to corals.10 The state of Hawaii has banned the sale of oxybenzone-bearing sunscreens, and many consumers (myself included) have switched to mineral-based formulations.11 However, recently some scientists and physicians have questioned the use of sunscreen, tout court, and in January 2019, Outside magazine reported on new evidence suggesting that conventional wisdom on the benefits of using sunscreen was wrong.

  The article focused on “rebel” dermatologist Richard B. Weller, who believes that sunlight lowers blood pressure, which in turn lowers the risk for heart disease and stroke—two of the biggest killers in the industrialized world. If Weller is right, then the widespr
ead, habitual use of sunscreen may have adverse health effects. In the article’s headline, the magazine demanded provocatively: “Is Sunscreen the New Margarine?”12

  The argument begins with the established correlation between sunshine and heart health. As the article reported, “high blood pressure, heart disease, stroke, and overall mortality all rise the farther you get from the sunny equator, and they all rise in the darker months.” But is sunshine the controlling factor? After all, food is often better in Mediterranean climes than in high latitudes (think Italy vs. Norway), and people eat more fresh fruits and vegetables and typically get more exercise in summer. Or perhaps life is more stressful when you have to deal with snow and ice and long, dark winter nights. However, at least one controlled study suggests that the causal factor is sunshine: when volunteers were exposed to the equivalent of thirty minutes of summer sunlight (without sunscreen), their blood pressure decreased. Moreover, there is a known mechanism to explain this relationship: nitric acid in the blood dilates blood vessels and thereby lowers blood pressure, and sun exposure increases blood nitric acid. Thus: sun exposure increases nitric acid, which decreases blood pressure, which reduces the risk of heart attack and stroke. Not bad for something that is readily available to most of us, free of charge. So ditch the sunscreen and head outside, right? That’s what the Outside magazine writer concluded, wondering “How did we get it so wrong?”

  Did “we” get it wrong? More to the point, did scientists (or physicians) get it wrong? If you only read this article, you would conclude that they did. The American Academy of Dermatologists, for example, advises “everyone” to use sunscreen, to routinely seek shade during the hours of 10 a.m. and 2 p.m., to wear protective clothing including long-sleeved shirts, pants, hats, and sunglasses, and to get Vitamin D through diet. “Don’t seek the sun,” they state without qualification.13 The Outside article calls this a “zero-tolerance” stand.

  However, there are a number of problems with the magazine’s conclusion. The article relies heavily on a study by Dr. Weller that has not yet been published. “Weller’s largest study is due to be published later in 2019,” we are told. Perhaps the study will be game-changing, but until it goes through peer review and is published, we are in no position to judge—and neither is Outside magazine.

  Weller is a coauthor on two papers that have been published—one in 2014 and one in 2018. Both relied on very small samples: twenty-four (eighteen men and six women) and ten participants (all male), respectively. No matter what they found, it would be unwise to summarily reject a huge body of existing science demonstrating the adverse effect of sun exposure (skin cancer) on the basis of such small studies.

  Moreover, what the studies found does not support the conclusion that the magazine article asserts.

  The 2014 paper found a small, transient decrease in diastolic blood pressure (e.g., from 120 to 117) associated with an exposure to artificial UVA light equivalent to thirty minutes in a Mediterranean region. The authors assert the significance of this result, arguing that “any amount of BP [blood pressure] reduction is protective against stroke and cardiovascular mortality … and the magnitude of changes observed in this study would appear to be large enough to account for the standardized mortality differences in populations living at different latitudes.” That might be true if the observed changes were sustained, but temporary blood pressure effects from nitrates are not strongly associated with long-term improved cardiovascular health.14 Unless people are staying outside a lot, the significance of this finding is unclear. Certainly, it is far from demonstrated.

  The 2018 paper found a transient effect on blood nitric acid levels and resting metabolic rate, but no effect at all on blood pressure. This immediately calls into question the alleged mechanism. Outside implied that the mechanism was known, but in fact it was a hypothesis that these studies were designed to test, and this test did not confirm it! Moreover, if something is a causal factor, we expect to find a dose-response relationship: more of the cause should produce more of the effect. The study found no dose-response relationship, forcing the authors to admit that their findings “contrasted” with their hypothesis. And both studies involved artificial, UVA-only light, leaving it unclear how well this any of this correlates with natural sun exposure.

  Dr. Weller may one day be proven right, but at present the alleged benefits of sunlight on blood pressure are not even close to proven. In contrast, the connection between sun exposure and skin cancer is.15 This is why dermatologists are advocates of sunscreen and sun avoidance, particularly for fair skinned people in Europe, North America, Australia, and New Zealand. Sun exposure can lead in the short run to painful sunburn, and in the long run to early aging of the skin and skin cancers, including deadly melanomas. The scientific evidence for this is abundant and well established.

  If we look at the guidelines offered by leading organizations of dermatologists in the United States, United Kingdom, and Australia, we do find some subtle differences of opinion and emphasis. In contrast to the American “zero-tolerance” stand, the Australian Cancer Council discusses the risks and benefits of sun exposure, providing “guidance on how much sun you need and how to protect yourself from getting too much.”16 They advise protection (hats, sunglasses, and sunscreen) when UV levels exceed three, which in most cases equates to protection in summer, but not winter.17 (This contrasts with the dominant advice in the United States, which is to use sunscreen year-round.) The argument in favor of some sun exposure is not, however, the effect on blood pressure, but on Vitamin D.

  “A balance is required between avoiding an increase in the risk of skin cancer by excessive sun exposure and achieving enough exposure to maintain adequate vitamin D levels.”18

  The British Association of Dermatologists also advocates a balanced approach:

  Nobody wants to spend the entire summer indoors, and indeed some sunshine, below sunburn level, can be good for us, helping the body to create vitamin D and giving many of us a feeling of general wellbeing as we enjoy outdoor summer activities.

  However, all too often we over-do our sun exposure which can lead to a range of skin problems, the most serious of which include skin cancer. Other summertime skin problems include sunburn, photosensitive rashes and prickly heat. In addition, sun exposure can worsen already existing conditions like rosacea.19

  The UK dermatologists stress the differences among people, noting that light-skinned people burn more easily and therefore need more protection than darker people. However, in the end, their advice (at least for the light-skinned among us) is more or less the same as the Americans’: protect yourself with a hat, clothing, and sunglasses, use sunscreen of at least SPF 30 on exposed skin, and stay in the shade at midday. Lest they be accused of being old-fashioned, they also suggest getting the World UV app, which provides “real time information on daily UV levels across over 10,000 locations across the globe.”20

  Where does this leave us? While there are some differences of opinion among dermatologists on how to balance the risks of skin cancer (and other forms of skin damage) with the benefits of sun exposure (Vitamin D metabolism), overall, physicians have a consensus on the benefits of protecting yourself from the sun. Scientists did not get this wrong, Outside magazine did.

  Of course, there may well be benefits to sun exposure that go beyond Vitamin D. Californians don’t need British doctors to tell them that being out in the sun makes them feel good, and there is clearly a reason people vacation in sunny places. Moreover, dermatologists—with their focus on protecting the skin from the sun’s ill effects—might be slow to attend to evidence that some degree of sun exposure is good for you. And it is interesting that American dermatologists seem to take a harder line than British and Australian doctors. But then Americans take a harder line than Australians on many things.

  Good decision-making requires integration of information. Being healthy involves more than just avoiding carcinogens.21 It also involves relaxation, recreation, stress reduction, an
d many other things that Europeans and Australians seems to be better at than Americans, and to which science has been a bit slow to attend. There is not only more on heaven and Earth than is dreamed of in our philosophies, but also more than is understood by our sciences.

  There is much we do not know, but that is no reason not to trust science on the things we do know. The argument for trust in science is not an argument for blind or blanket trust. It is an argument for warranted confidence against unwarranted skepticism in scientists’ findings in their domains of expertise.

  NOTES

  Introduction

  1. As Naomi Oreskes has argued in a previous book coauthored with Erik M.Conway, Merchants of Doubt, and a documentary film of the same name.

  2. See CBS Evening News, January 30, 2019, https://www.cbsnews.com/video/how-long-will-the-cold-snap-last/; and PBS Newshour, January 30, 2019, segment with Dr. Jennifer Francis, https://www.pbs.org/newshour/show/why-the-midwests-deep-freeze-may-be-a-consequence-of-climate-change.

  3. Princeton University Press secured anonymous expert reviews of an earlier version of the manuscript, and their detailed and helpful comments have been of great help in revising and improving the manuscript.

  4. As I once heard the political philosopher Joseph Cropsey say, at a seminar organized by Harvey C. Mansfield in the Harvard Government Department: while the greatest minds rise above many of the prejudices of their times, no one rises above all the prejudices of their times.

  Chapter 1. Why Trust Science? Perspectives from the History and Philosophy of Science

  1. I hesitate to use the word crisis, but on the other hand, rejection of the science of vaccines is a matter of life and death, and rejection of climate science has now become so.