The free speech controversies roiling Big Tech have now reached the scientific sphere.

In mid-February, the Wall Street Journal published an opinion piece by John Hopkins professor of medicine and public health  Martin Makary arguing that a combination of vaccines and natural infections would result in herd immunity in many parts of the United States by the end of April. Facebook quickly flagged the editorial as “misleading” and having “very low overall scientific credibility.”

Whatever one may think of Makary’s claim about herd immunity, he is a distinguished scientist. In addition to authoring over two hundred papers and a New York Times bestselling book, Makary is currently the editor in chief of the leading clinical news site  Medpage Today. And his case is no isolated matter.

Over the past few months, Facebook, Google, and Twitter have engaged in multiple acts of censorship against scientists holding a range of views on COVID-19 and the public health response to it. This censorship sets a dangerous precedent — allowing large, unaccountable corporations to set themselves up as arbiters of not only acceptable public speech, but also of what constitutes acceptable science.

The scientists being censored by the world’s largest technology companies aren’t fringe figures. They are leading thinkers employed at prestigious universities — people whose research has been cited tens of thousands of times. Whether or not one agrees with the opinions they express, the history of science teaches us that scientific inquiry requires vigorous debate. Yet in the name of fighting “disinformation,” tech companies have repeatedly muzzled scientific debate and public dialogue in recent months.

In a separate incident, Facebook censored a post linking to a peer-reviewed Lancet article that argued for the airborne transmission of SARS-CoV-2 through aerosols. This viewpoint is in conflict with the official World Health Organization (WHO) explanation which emphasizes transmission through small droplets rather than smaller, aerosolized particles.

Like Makary, the authors of the Lancet article include world-renowned experts on aerosols. Kimberly Prather of the Scripps Institute of Oceanography at UC San Diego is the distinguished chair in atmospheric chemistry and director of the NSF Center for Aerosol Impacts on Chemistry of the Environment, while coauthor Jose-Luis Jimenez is among the most cited aerosol researchers in the world.

Whether one comes down on the side of droplet transmission or aerosolized particle transmission, it is disturbing that Facebook moderators have the power to censor links to a peer-reviewed article in a leading health journal — particularly one with significant public health implications. The article’s authors insist that “reducing airborne transmission of virus requires measures to avoid inhalation of infectious aerosols, including ventilation, air filtration … attention to mask quality and fit, and higher-grade protection for health-care staff and front-line workers.”

Facebooks justifies its behavior as “fact-checking,” but the procedure it uses to vet scientific claims is murky. In Makary’s case the social media company contracted its fact-checking to a newly formed third-party fact site, healthfeedback.org. But how the fact-checkers are chosen is less clear, prompting oncologist and University of California San Francisco professor Vinay Prasad to opine after investigating the matter that Facebook seems to choose its “fact-checkers” based on how many Twitter followers they have.

In another incident of censorship, in March Google-owned YouTube removed the recording of an official public hearing on the pandemic that featured Florida governor Ron DeSantis, Scott Atlas and Jay Bhattacharya of Stanford University, Sunetra Gupta of Oxford University, and Martin Kulldorff of Harvard University. The latter three scientists are originators of the Great Barrington Declaration, a much-debated document arguing against lockdowns and for a strategy of focused protection for the elderly that was adopted in Florida.

YouTube’s explanation for its decision to remove the video was that it “contradicts the consensus of local and global health authorities” in regards to the efficacy of masks among children. To be sure, DeSantis is reviled by progressives, and many scientists and public health experts vehemently oppose the recommendations made in the Great Barrington Declaration. But it’s hard to imagine a more Orwellian justification for censoring a government hearing at which public health policies that would impact millions of people were being discussed.

Google’s actions are especially troubling because, as is often true at the intersection of science and public policy, there is no single global consensus — in this case regarding the question of masks and children. For example, even though the Centers for Disease Control and Prevention (CDC) recommends masks for all children above the age of two, the WHO recommends against masks for children under five and masks for children ages six to eleven only when “there is widespread transmission in the area where the child resides.” Meanwhile, the public health agencies of Norway, Sweden, and Denmark, countries which have undertaken very different strategies to manage the pandemic, all agree that face masks are not necessary for children under twelve.

Given the wide spectrum of official opinions on the matter, debate is essential. Science and public understanding both suffer when mammoth tech companies like Google and Facebook are given unilateral authority to censor and stifle scientific discussion and debate.

A pattern has emerged in these and many other recent incidents of censorship: an appeal to scientific authority or perceived consensus to justify the stifling of minority viewpoints. But an appeal to scientific authority is not a substitute for scientific debate. The history of science is littered with well accepted “facts” and theories that were later revealed to be dogmatic falsehoods.

The most notorious example is the field of eugenics — a discipline dedicated to improving the “genetic quality” of the human population through selective breeding and exclusion of disfavored groups perceived to have undesirable traits (disabled people, “criminals,” those with “low-intelligence,” African Americans, Jews, Eastern Europeans). It is hard to believe now, but at the beginning of the twentieth century eugenics was considered a respectable, cutting-edge scientific discipline. Eugenics courses were being developed and taught at leading universities like Cornell, Harvard, Chicago, and MIT. The “science” of eugenics was being used to help formulate and justify restrictive immigration policies like those in the Immigration Act of 1924.

But even at the height of the eugenics craze, scientists such as the “Father of American Anthropology” Franz Boas argued against consensus views about inherent group differences and the biological origins of racial and ethnic inequality. Boas understood the importance of protecting the right of scientists to hold and express dissenting scientific opinions. In a letter to the philosopher John Dewey, Boas wrote:

“There are two things to which I am devoted: absolute academic and spiritual freedom, and … the fight against all forms of power policy of states or private organizations. This means a devotion to principles of true democracy.”

Boas understood that when we allow private organizations — like Facebook, Google, and Twitter — to police scientific discourse, we abdicate our commitment to free scientific inquiry. Despite public protestations to the contrary, tech companies have no intrinsic commitment to fundamental scientific values like truth and integrity. Instead, their policies reflect their priorities: profitability and market share.

History has proven that, like all human institutions, the enterprise of science is fallible. Individual scientists are often wrong. Sometimes, even the scientific consensus is mistaken. The only safeguard is what Boas called “absolute academic and spiritual freedom” — a freedom that is only possible if we rein in the ability of Big Tech to set the terms of scientific debate.