FROM VACCINATIONS TO CLIMATE CHANGE, we make decisions every day that involve us in scientific claims. Are genetically modified crops safe to eat? Do childhood vaccinations cause autism? Is climate change an emergency?
In recent years, many of these issues have become politically polarized, with people rejecting scientific evidence that misaligns with their political preferences. When Greta Thunberg, the youthful climate activist, testified in Congress recently, submitting as her testimony the IPCC 1.5° report , she was asked by one member why should we trust the science. She replied, incredulously, “because it’s science!” 
For several decades, there has been an extensive and organized campaign intended to generate distrust in science, funded by regulated industries and libertarian think-tanks whose interests and ideologies are threatened by the findings of modern science. In response, scientists have tended to stress the success of science. After all, scientists have been right about many things, from the structure of the Universe (Earth revolves around the Sun, not vice-versa.) to the relativity of time and space (Relativistic corrections are needed to make global positioning systems work.).
Thunberg’s answer isn’t wrong, but for many people it’s not persuasive. After all, just because scientists more than 400 years ago were right about the structure of the solar system doesn’t prove that a different group of scientists are correct about a different issue today.
AN ALTERNATIVE TO THE QUESTION, “Why trust science?” is that scientists use “the scientific method.” If you’ve got a high-school science textbook lying around, you’ll probably find that answer in it. But this answer is wrong. What is typically asserted to be the scientific method – develop a hypothesis, then design an experiment to test it – is not what scientists actually do. Historians of science have shown that scientists use many different methods, and these methods have changed with time. Science is dynamic. New methods get invented, old ones are abandoned, and at any particular juncture scientists can be found doing many different things.
That’s a good thing, because the so-called scientific method doesn’t always work. False theories can yield true results, so even if an experiment works, it doesn’t prove that the theory it was designed to test is true. There also might be different theories that could yield that same experimental result. Conversely, if the experiment fails, it doesn’t prove the theory is wrong; it could be that the experiment was badly designed or there was a fault in one of the instruments.
If there is no identifiable scientific method, then what is the warrant for trust in science? How can we justify using scientific knowledge – as Greta Thunberg and many others insist that we must – in making difficult personal and public decisions?
The answer is not the methods by which scientists generate claims but the methods by which those claims are evaluated. The common element in modern science, regardless of the specific field or the particular methods being used, is the critical scrutiny of claims. It’s this process of tough, sustained scrutiny that works to ensure that faulty claims are rejected and that accepted claims are likely to be right.
The common element in modern science is the critical scrutiny of claims.
A scientific claim is never accepted as true until it has gone through a lengthy process of examination by fellow scientists. This process begins informally, as scientists discuss their data and preliminary conclusions with their colleagues, their postdocs and their graduate students. Then the claim is shopped around at specialist conferences and workshops. This may result in the scientist collecting additional data or revising the preliminary interpretation. Sometimes it leads to more radical revision, like redesigning the data-collection program, or scrapping the study altogether if it begins to look like a lost cause. If things are looking solid, the scientist writes up the results. At this stage, there’s often another round of feedback, as the preliminary write-up is sent to colleagues for comment.
Until this point, scientific feedback is typically fairly friendly. But the next step is different: once the paper seems ready, it is submitted to a scientific journal, where things get a whole lot tougher. Editors deliberately send scientific papers to people who are not friends or colleagues of the authors, and the job of the reviewer is to find errors or other inadequacies in the paper. We call this process “peer-review” because the reviewers are scientific peers – experts in the same field – but they act in the role of superiors who have both the right and the obligation to find fault. Reviewers can be pretty harsh, so scientists need to be thick-skinned and accept criticism without taking it personally. Editors sometimes weigh in too, and often their contributions are not all that nice, either.
Only after the reviewers and editor are satisfied that recognizable errors and inadequacies have been fixed is the paper accepted for publication and enters into the body of science. Even then, the story is not over, because if serious errors are detected after publication, journals may issue errata, or even retract the paper.
Why do scientists put up with this difficult and sometimes nasty process? Many don’t. A lot of them drop out along the way and move into other professions. But those who persist can see how it improves the quality of their work. Philosopher of science Helen Longino  has called this process of critical scrutiny transformative interrogation: interrogation, because it’s tough, and transformative because over time our understanding of the natural world is transformed.
A KEY ASPECT OF SCIENTIFIC JUDGMENT is that it is not done individually; it is done collectively. It’s a cliché that two heads are better than one. In modern science, no claim gets accepted until it has been vetted by dozens, if not hundreds of heads. In areas that have been contested, like climate science and vaccine safety, it’s thousands. This is why we are generally justified in not worrying too much if a single individual scientist, even a famous one, dissents from the consensus. There are many reasons why an individual might dissent: he might be disappointed that his own theory didn’t work out, bear a personal grudge, or have an ideological ax to grind. She might be stuck on a detail that just doesn’t change the big picture, or enjoy the attention she gets for promoting a contrarian view. Or he might be an industry shill.
The odds that the lone dissenter is right – and everyone else is wrong – are not zero, but so long as there has been adequate opportunity for the full vetting of his and everyone else’s claims, they are probably in most cases close to zero. This is why diversity in science is important. The more people looking at a claim from different angles, the more likely they are to identify errors and blind spots. It’s also why we should have a healthy skepticism towards brand-new claims. It may take years or sometimes decades for this process to unfold.
Excerpted from: Naomi Oreskes, “Science Isn’t Always Perfect – But We Should Still Trust It,” Time (24 October 2019). Read More.
For a more detailed, scholarly discussion, see Naomi Oreskes, Why Trust Science? (Princeton University Press, 2019; paperback edition to appear in March 2021).
1. UN Intergovernmental Panel on Climate Change Special Report, “Global Warming of 1.5°C,” October 2018.
2. “Listen to the science, Thunberg tells Congress,” You Tube, 18 September 2019.
3. Helen Longino, Clarence Irving Lewis Professor of Philosophy, Stanford University.
See also Naomi’s TED talk on the subject, “Why We Should Trust Scientists.“
Naomi Oreskes is the Charles Lea Professor of the History of Science and Affiliated Professor of Earth and Planetary Sciences at Harvard University. A Guggenheim Fellow, she is the author or coauthor of seven books, including Merchants of Doubt (2010), Discerning Experts (2019), and Why Trust Science? (2019). Her articles and essays on climate change have appeared in the New York Times, Washington Post, Los Angeles Times, and The Times of London. She was an early Orcas Currents lecturer.