기원전 4세기. 모든 학문의 아버지로 불리는 아리스토텔레스는 하늘에 보이는 우주는 지구를 중심으로 원운동을 한다는 ‘천동설’을 주장했다. 1000년이 넘게 천동설은 정설이자 진리로 여겨졌다. 하지만 망원경의 발명으로 우주를 관찰하게 되면서 지구가 우주의 중심이라고 하면 설명이 되지 않는 현상들이 발견되기 시작한다.
니콜라우스 코페르니쿠스는 ‘천체의 회전에 관하여’라는 책을 펴내며 지동설을 최초로 주장했다. 당시 분위기라면 이 책은 ‘금서’로 지정되어야 했지만 아무일도 벌어지지 않았다. 책의 내용이 너무 어려워 이해하지 못했기 때문이다. 하지만 이 책을 이해하고 감명받은 인물이 있었다. 바로 갈릴레오 갈릴레이다.
갈릴레이는 일종의 해설서인 ‘두 우주 체계에 대한 대화’를 1632년 발간했다. 책의 제목에서 가늠할 수 있듯, 천동설을 주장하는 과학자들과 대화하는 방식으로 구성된 책이다. 천동설로는 설명이 어렵지만, 지동설로는 설명할 수 있는 ‘관측 결과’들을 제시하며 지동설을 간접적으로 지지했다. 인류 최초의 과학대중서인 셈이다.
천동설은 틀린 지식이지만 관측, 예측, 수정, 반증 그리고 지동설로 변하는 과학혁명 등 과학의 중요한 요소들을 모두 갖추고 있는 아주 좋은 과학, 칼 세이건의 말을 빌리면, ‘과학은 지식이 아니라 생각하는 방식’이다”
‘과학은 생각하는 방식이다’라는 말을 어떻게 이해해야 할까. 현대인들은 아리스토텔레스도 몰랐던 지동설을 알고, 찰스 다윈보다 진화론에 대한 지식이 많다. 하지만 지식이 많다고 현대인들을 ‘좋은 과학자’라고 평가하긴 어렵다. 맞지 않는 천동설을 발전시켜 온 아리스토텔레스, DNA의 구조도 몰랐던 찰스 다윈이 후대에 좋은 과학자라고 불린다. 좋은 과학이란 지식이 아니라 의심하고, 관측하고, 논리를 만들며 생각하는 과정이란 의미다.
태양계를 100억 분의 1로 축소시키면 월드컵경기장 300개를 합한 크기가 된다. 여기서 태양은 지름이 14cm 정도 되는 공, 지구는 볼펜 촉 정도의 크기에 해당한다. 볼펜 촉에서도 아주 작은 존재인 인간이 우주 전체를 내려다보는 일은 앞으로도 없을 것이다. 천동설이 맞는지, 지동설이 맞는지를 직접 관찰할 수는 없지만, 당시의 과학혁명처럼 과학자들은 논리를 통해 무엇이 진실인지를 찾아간다.
당시의 권위인 ‘아리스토텔레스 주의’에 빠져 과학혁명이 일어나지 않았다면, 과학은 지금처럼 발전하지 못했을 것”, “과학은 의심에 대한 잠정적인 답을 찾아가는 과정이다”
Science, tentative answers to doubts
definition of science
Why Doubt Is Essential to Science
If people don’t understand how science works, they can’t properly understand how to think about new findings
The confidence people place in science is frequently based not on what it really is, but on what people would like it to be. When I asked students at the beginning of the year how they would define science, many of them replied that it is an objective way of discovering certainties about the world. But science cannot provide certainties. For example, a majority of Americans trust science as long as it does not challenge their existing beliefs. To the question “When science disagrees with the teachings of your religion, which one do you believe?,” 58 percent of North Americans favor religion; 33 percent science; and 6 percent say “it depends.”
But doubt in science is a feature, not a bug. Indeed, the paradox is that science, when properly functioning, questions accepted facts and yields both new knowledge and new questions—not certainty. Doubt does not create trust, nor does it help public understanding. So why should people trust a process that seems to require a troublesome state of uncertainty without always providing solid solutions?
As a historian of science, I would argue that it’s the responsibility of scientists and historians of science to show that the real power of science lies precisely in what is often perceived as its weakness: its drive to question and challenge a hypothesis. Indeed, the scientific approach requires changing our understanding of the natural world whenever new evidence emerges from either experimentation or observation. Scientific findings are hypotheses that encompass the state of knowledge at a given moment. In the long run, many of are challenged and even overturned. Doubt might be troubling, but it impels us towards a better understanding; certainties, as reassuring as they may seem, in fact undermine the scientific process.
Scientists understand this, but in the dynamic between the public and science, there are two significant pitfalls.
The first is a form of blind scientism—that is, a belief in the capacity of science to solve all problems. The popular narrative of science is linear, embodied by heroic researchers who work selflessly for the good of humanity. Indeed, some scientists promote this attractive public image of their work. But this narrative ignores the ubiquity of controversy, conflict and error at the very heart of the scientific world. Such an idealized representation tends to turn science into an unquestionable set of beliefs. In fact, however, the power of science lies precisely in its capacity to generate discussion and even discord.
The second pitfall is a form of relativism borne out of a lack of confidence in the very existence of truth. It develops when science is divorced from method and viewed as just another claim in the marketplace of ideas. A Pew Research study shows that 35 percent of Americans think the scientific method can be used to produce “any result a researcher wants.” Once the scientific approach has been delegitimized, then all hypotheses, including the most outlandish and irrational ones, can be taken as credible. So, hidden in this conceit of a democratic “marketplace of ideas” is a particularly virulent form of relativism that approaches nihilism.
Such examples of relativism about issues including climate change and, most recently, the COVID-19 pandemic—have significantly contributed to the proliferation of fake news and conspiracy theories. The diffusion of fake news is facilitated by the difficulty of a large majority of Americans in distinguishing between fact and opinion. Factual news can be proved or disproved by objective evidence, while opinion is an expression of the beliefs and values of the speaker.
In an effort to combat misinformation, scientists may overcompensate by accelerating their research, or publicizing their findings prematurely. This can spur dialogue about science but, with serious side effects. Some scientists have yielded to public pressure by rushing to provide theories about and potential cures for COVID-19. In an August article in the Annals of Internal Medicine, for example, Doroshow, et al. observe that “Although this boom has already begun to transform our response to the pandemic for the better, medical and scientific responses to past crises suggest that urgency may also result in compromised research quality and ethics, which may in turn jeopardize public faith in government and science, waste precious resources, and lead to the loss of human life.”
The scientific process itself has been called into question during the pandemic in cases where the very institutions and peer review process that were supposed to check scientific results failed to detect scams. In the words of editor Richard Horton, a study on hydroxychloroquine first published by The Lancet and then retracted within weeks, was a “monumental fraud”.
So how to regain public trust in science when the public is looking for certainties and when those who are supposed to impersonate doubt seem to be fickle or dogmatic?
A more realistic understanding of how science works can contribute to a better comprehension of the decisive role of doubt and skepticism in the scientific process. Indeed, science is not a linear path leading from one success to another, but rather a constant reevaluation of hypotheses. Failures are part of the scientific process and should be taught along with successes.
It is, therefore, not so much the content of scientific discoveries that should be highlighted, but the understanding of the scientific process itself that must be enhanced. No one expects the public at large to fully understand all discoveries or to be able to arbitrate between possible treatments. But what must be reaffirmed is that in science, doubt is not a vulnerability but a strength. The scientific approach often leads to dead ends, but sometimes it leads to fundamental discoveries that no other approach has ever achieved.
Author’s note: I wish to thank Janet Browne, André Grjebine, Rebecca Lemov for their constant support and critique, Michael Connolly, Thomas Grjebine, David Jones, Juan Palacios, Sara Press, Yvan Prkachin and Sylvia Ullmo for their insightful comments and suggestions.