These days, if Karl Popper is remembered at all, he is usually remembered for The Open Society and Its Enemies—his blistering two-volume attack on the philosophical foundations of Fascism and Marxism. In fact, however, Popper was not primarily a political philosopher. Instead, he devoted most of his long life to studying the growth of scientific knowledge.

In The Logic of Scientific Discovery, Popper provided what he called “a logical analysis of … the method of the empirical sciences.” In the course of that analysis, he demonstrated that, contrary to what had previously been assumed, the scientist’s tools—rational thought and careful observation—cannot be used effectively to ascertain truth; they can, however, be used very effectively indeed to discover and eliminate error.

Building on that insight, in that same work, and in many subsequent works, Popper developed a remarkably original and brilliant unified theory of knowledge. He summarized that theory in one of those subsequent works by saying:

It is a theory of reason that assigns to rational arguments the modest and yet important role of criticizing our often mistaken attempts to solve our problems. And it is a theory of experience that assigns to our observations the equally modest and almost equally important role of tests which may help us in the discovery of our mistakes. Though it stresses our fallibility it does not resign itself to skepticism, for it also stresses the fact that knowledge can grow, and that science can progress—just because we can learn from our mistakes. 

The way in which knowledge progresses, and especially our scientific knowledge, is by unjustified (and unjustifiable) anticipations, by guesses, by tentative solutions to our problems, by conjectures. These conjectures are controlled by criticism; that is, by attempted refutations, which include severely critical tests. They may survive these tests; but they can never be positively justified: they can neither be established as certainly true nor even as ‘probable.’ … Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problem which we are trying to solve. This is how we become better acquainted with our problem, and able to propose more mature solutions: the very refutation of a theory–that is, of any serious tentative solution to our problem–is always a step forward that takes us nearer to the truth. And this is how we can learn from our mistakes. 

As we learn from our mistakes our knowledge grows, even though we may never know–that is, know for certain. Since our knowledge can grow, there can be no reason here for despair of reason. And since we can never know for certain, there can be no authority here for any claim to authority, for conceit over our knowledge, or for smugness. 

At this point, the long-suffering reader may be asking, what is all this philosophical theory doing in a Legal Update? The answer is that it sheds important light on a topic I’ve been writing about for several years, namely, the use of legal sanctions to silence those who espouse heterodox views about climate change. (For previous discussions, see here, here, and here.) I’m bringing Popper’s theory of knowledge into the discussion to make the point that, whatever else they may be, these attacks on freedom of speech should be seen as attacks on the scientific method itself. That’s been true all along, but a recently filed lawsuit makes it crystal clear.

In December of 2015, the National Academy of Sciences published an article purporting to show that by 2050 it will not only be possible, but relatively easy, for the continental United States to meet 100 percent of its energy needs with just three renewable power sources: wind, water, and solar. The lead author was Stanford University professor Mark Jacobson, and he was joined by several co-authors.

In June of this year, the National Academy of Sciences published a response that purported to identify several errors in the original paper and disputed its conclusion. The lead author of the second article was Christopher Clack, who has a Ph.D. in applied mathematics and plasma physics and worked for the National Oceanic and Atmospheric Administration at the University of Colorado before becoming CEO of the grid modeling firm Vibrant Clean Energy. He was joined by 21 co-authors who are also eminent scientists.

So far so good. One group of scientists made the kind of “bold conjecture” that powers the scientific project forward, and another group of scientists subjected that conjecture to the kind of rigorous criticism that helps scientists learn from their mistakes and get closer to the truth. According to Popper, this is exactly the way science should proceed.

What happened next, however, wasn’t so good at all. Instead of responding to his critics’ speech with more speech, Jacobson took steps to punish some of them (and, no doubt, intimidate the others) by filing a $10 million defamation claim against Christopher Clack and the National Academy of Sciences.

Given the current state of public discourse in this country, one might have expected Jacobson’s resort to law to be accepted, or even applauded, by his peers and by the public. I’m happy to say, however, that that is not what happened. Not only have many people objected to the lawsuit, but they have also objected, at least in part, because they understand that criticism plays a vital role in science and that an attack on scientists’ freedom to criticize is an attack on science itself.

In a post at Reason’s Hit and Run blog, Lindsay Marcello (Carolina Journal) reported two hostile responses:

David Victor, one Clack’s co-authors and the co-director of the Laboratory on International Law and Regulation at University of California-San Diego, told the San Diego Union-Tribune, “It is unfortunate that Mark Jacobson has decided to pursue this legally as opposed to openly, in the scientific tradition.”

Environmental Progress, a research and policy organization advocating for sustainable energy, called the lawsuit an “appalling attack on free speech and scientific inquiry.”

And she added one of her own:

By taking his critics to court, Jacobson is telling the world his ideas cannot be challenged, echoing the argument for “settled science” deployed in the debate over climate change. …

What incentive is there to add to or challenge the evidence of a scientific theory if that idea can’t be challenged? The truth is best found through open debate, not by silencing your critics with lawsuits.

Gavin Schmitt (NASA) tweeted his displeasure:

Using court to resolve sci issues? Generally a bad idea.

And so did Roger Pielke, Jr. (University of Colorado Boulder):

With this lawsuit, climate science again showing its ugly side. Anything to silence opponents. Scientific back-and-forth not welcome.

Anything less than unified, strong denunciation of Jacobson lawsuit by science organizations is unacceptable. These guys destroying science.

Judith Curry (Georgia Institute of Technology, ret.) wrote:

I am just speechless. …

In many ways, this is much worse than any of Michael Mann’s lawsuits alleging defamation of character — Jacobson’s lawsuit seeks to settle a genuine scientific disagreement in the courts.

Jonathan Adler (Case Western Univ. School of Law) explained that:

The idea that academic researchers should turn to court when their work is criticized or contradicted by other researchers is a pernicious one, challenging the sort of robust inquiry upon which scientific research and the discovery of knowledge require. It is absolutely essential that researchers are free to posit hypotheses and subject others’ hypotheses to critique. This inevitably entails not just questioning other researchers’ conclusions, but also pointing out potential errors and mistakes.

Even Keith Pickering (Daily Kos) was displeased:

It is hard to overstate how totally bonkers this lawsuit is. … In science, ideas are accepted or rejected on their own merits, and any process that undermines that merit-based approach — including a legal process — won’t change the mind of any principled scientist. “Don’t say I’m wrong or I’ll sue you” is precisely the opposite of the scientific method. If anyone is responsible for trashing Jacobson’s reputation as a scientist it is Jacobson himself, and this lawsuit clinches it.

I’m surprised, and pleased, find the Daily Kos on the right side of an issue, but I’m not going to give it the last word. Instead, I’m going to end with a couple of additional excerpts from the Environmental Progress piece by Michael Shellenberger mentioned above:

What Jacobson has done is unprecedented. Scientific disagreements must be decided not in court but rather through the scientific process. …

Scientists and energy analysts should not be intimidated. We must stand up to bullies.

Shellenberger is right. We must stand up to bullies. I hope the Superior Court of the District of Columbia dismisses this case with a sharp rebuke. I hope Christopher Clack and the National Academy of Sciences countersue, and I hope they are awarded treble damages and costs against Mark Jacobson. And I hope the court imposes sanctions on Jacobson’s attorneys under Rule 11 of the Federal Rules of Civil Procedure, which prohibits pleadings “for any improper purpose, such as to harass, cause unnecessary delay, or needlessly increase the cost of litigation.”