A group of international scientists is walking back major claims they’d made in the journal Nature about the rate at which the earth’s oceans are warming. A newly published note from the study’s co-author, Ralph Keeting, makes it plain that these researchers still believe the oceans are warming at an alarming rate, but they now acknowledge that procedural mistakes “that came to our attention” created an unacceptably large margin of error in their results.

That “came to our attention” line conceals the most important aspect of the story. These scientists work out of Princeton University, the U.S. National Center for Atmospheric Research, and various international institutions that make up the much lionized “scientific consensus” on climate change. And they had their landmark study debunked by an independent global-warming skeptic of no institutional standing named Nicholas Lewis.

Where did Lewis debunk the doomsayers? No, not in the esteemed pages of Nature but in a blog post at a website called Climate Etc., a small, dissenting dot in the vast universe of online science discussion. Lewis wrote: “The findings of the…paper were peer-reviewed and published in the world’s premier scientific journal and were given wide coverage in the English-speaking media.” He went on: “Despite this, a quick review of the first page of the paper was sufficient to raise doubts as to the accuracy of its results. Just a few hours of analysis and calculations, based only on published information, was sufficient to uncover apparently serious (but surely inadvertent) errors in the underlying calculations.”

Imagine a world in which we heard only from those pushing and applauding mainstream opinion. Or, perhaps, don’t imagine it; prepare for it. Only two days after Lewis wrote his post, the New York Times published an interview with Google CEO Sundar Pichai. The Times’s David Gelles asked Pichai why tech companies couldn’t just ban propaganda and misinformation from social-media platforms as they’ve done with pornography and violence. Pichai explained that it could be hard to figure out what exactly constitutes propaganda and misinformation. He then offered examples to explain the challenge: “Should people be able to say that they don’t believe climate change is real? Or that vaccines don’t work? It’s just a genuinely hard problem.”

A hard problem. The CEO of Google thinks that the question of whether or not to permit minority opinions on social media is a hard problem. Let’s hope Big Tech works that one out wisely because if the thumbs-down side of the debate wins, the likes of Nicholas Lewis and Climate Etc. would be lumped in with anti-vaxxers and banished from the digital public square. So when faulty, tendentious science appears in places like Nature, it will go uncorrected—by design. Pinchai’s understanding of climate-change skepticism as propaganda and misinformation is itself an example of the propaganda and misinformation that dominates public discourse.

Many in the liberal mainstream have determined that their convictions rest on a priori knowledge. That is, knowledge that doesn’t rely on evidence or experience. They know things because these things are true. They sometimes apply this to claims of sexual assault, and they usually apply it to climate change. Keeting, for example, says that he’s certain of the Nature study’s findings even though those findings are uncertain. In actual fact, such matters belong to the realm of a posteriori knowledge. We need evidence to determine whether they are true or false. But if mainstream institutions can pathologize dissent, they’ll never need to provide evidence for the convictions they peddle.

It’s true that the U.S. Constitution protects citizens against totalitarian government. But for all the Founders’ stunning foresight, they couldn’t have envisioned a world in which non-government parties would close in on a cultural monopoly of public debate. The forces of obscurantism are making an end-run around our brilliantly conceived checks and balances and appealing to Big Tech to shut down dissent. Constitutional guardrails constrain demagogic presidents. But CEOs, social-media behemoths, and academic institutions are free to dictate the terms of reality as they see fit. Against them, we have people like Nicholas Lewis. That’s about it.