Tucker Carlson, Karl Popper, and How Science Really Works

Are successful scientific theories the result of cumulative evidence over many trials and tests, or are they those not yet falsified? By guest columnist Eric Denton

In my book Why People Believe Weird Things I offered this definition of how science works:

Science is a set of methods designed to describe and interpret observed or inferred phenomenon, past or present, aimed at building a testable body of knowledge open to rejection or confirmation

That is, science is something we do, an action, a verb, to describe what we see in the lab or field or world, or interpret what we think we see, since the facts never just speak for themselves but must be interrupted through some model or theory (facts are “theory laden”). Sometimes we see things directly, but sometimes we must infer their presence indirectly, for example, exo-planets are inferred by their effects on their home star, either by the perturbation of the star’s motion or by the amount of emitted light that dims when the planet passes in front of it that astronomers can detect. Because many sciences are historical in nature—cosmology, geology, paleontology, archaeology, and history—we have to infer information about them from indirect sources. To put this mouthful more briefly:

Science is a method to explain the world that is testable and open to change.

My favorite rendition of this process comes from a 1964 lecture at Cornell University by the Nobel laureate physicist Richard Feynman:

If it disagrees with experiment, it’s wrong. In that simple statement is the key to science. It doesn’t make any difference how beautiful your guess is, how smart you are, who made the guess, or what his name is. If it disagrees with experiment, it’s wrong. That’s all there is to it.

Is that all there is to it? In this week’s Skeptic column a scholar of Karl Popper, Eric Denton, considers this question, in the context of what happens when people do not understand how science works, as evidenced by Tucker Carlson’s recent appearance on Joe Rogan when he revealed his ignorance about the theory of evolution.

—Michael Shermer

Eric Denton is a writer and podcaster whose primary focus is epistemology; in particular, Popperian epistemology. He separates the wheat from the chaff by subjecting popular science and philosophical writings to severe criticism. His mission is to promulgate critical rationalism to his readers and listeners. Eric is currently working on a book which revolves around the work of Sir Karl Popper.

Tucker Carlson, Karl Popper, and How Science Really Works

Eric Denton 

“Theories (scientific or otherwise) are trials, inventions; they are not the results of many observations; they are not derived from many data.”

—Karl Popper, All Life Is Problem Solving

On the April 23, 2024 episode of the wildly popular podcast The Joe Rogan Experience, former preppy now turned populist right-wing firebrand Tucker Carlson confidently declared that “the theory of evolution as articulated by Darwin is like, kinda not true.” 

“In what sense?” asked a bemused Joe Rogan.

“Well, in the most basic sense,” Carlson continued. “The idea that—you know—all life emerged from a single organism and overtime—and—there would be a fossil record of that and there’s not.” 

Rogan interjected by mentioning the existence of transitional fossils; fossils exhibiting adaptations to particular environments.

Carlson quickly appropriated this explanation for his own ends: “there’s tons of record of adaptation and you see it, in your own life. I mean, I have a lot of dogs—I see adaptation in dogs….” He rambled on a bit more before concluding, “but no, there’s no evidence at all that—none—zero—that, you know, people, you know, evolved seamlessly from a single cell amoeba; no, there’s not—there’s not—there’s no chain in the fossil record of that at all.”

I’m afraid Carlson’s blathering is demonstrative of how a great many people think about the methods of science and the growth of knowledge. Like him, multitudes think we acquire knowledge through our senses. This is false. But before continuing, let me supplement this claim with a quote from the philosopher of science Karl Popper’s book The Logic of Scientific Discovery, “I readily admit that only observation can give us ‘knowledge concerning facts’, [here Popper is quoting philosopher Hans Hahn] and that we can ‘become aware of facts only by observation’.” But then Popper reflects, “but this awareness, this knowledge of ours, does not justify or establish the truth of any statement.” So, to be sure, we can learn facts using our senses—unjustified tentative facts—but this isn’t where knowledge comes from. 

On November 24, 1859, Charles Darwin introduced what philosopher Daniel Dennett would later call the “best idea anyone has ever had.” This idea was the theory of evolution by natural selection. “In a single stroke,” Dennett asserts in his book Darwin’s Dangerous Idea, “the idea of evolution by natural selection unifies the realm of life, meaning, and purpose with the realm of space and time, cause and effect, mechanism and physical law.” The evolutionary biologist Richard Dawkins waxes eloquent about the simplicity and elegance of natural selection in his book The Blind Watchmaker, following up with a curious question, “how could such a simple idea go so long undiscovered by thinkers of the caliber of Newton, Galileo, Descartes, Leibnitz, Hume and Aristotle?” I’ve often asked this myself.

A couple of centuries before Darwin, in 1610, Galileo Galilei observed, among other things, the phases of Venus (shadows caused by its relation to the sun) through his newly improved homemade telescope, thereby corroborating the heliocentric theory of our solar system; a theory put forth by Nicolaus Copernicus about a half century earlier. With this discovery—in the minds of many—we had finally found the key to making scientific progress: observation! It seemed as if Galileo had simply pointed his telescope at Venus, observed it circling the sun, and voilà, the truth was revealed. But is this what really happened? I’ll argue below that this is mistaken. But first we need context.

About a decade after the corroboration of the heliocentric theory, the philosopher Francis Bacon independently put forth a scientific method that vaguely resembled what Galileo had done. Or at least it seemed so under indiscriminate viewing. His method proposed that, in order to make scientific progress, we must derive general theories from specific observations. For example, if—up to now—you’ve only ever come across white swans in your life, according to Bacon’s method you can logically deduce that all swans are white; you notice a pattern, then derive a theory. “We must not imagine or invent,” Bacon writes in his book Novum Organum, “but discover….”

The title page illustration of Francis Bacon’s Novum Organum

In other words, we simply allow knowledge to enter our brains through our senses. Sound familiar? This is precisely how Tucker Carlson demonstrated his method of understanding the natural world. “I see adaptation in dogs,” he said. From this he forms the theory that adaptation is “clearly, obviously true,” but then says “there’s no evidence at all that… people… evolved seamlessly from a single cell amoeba.” Notice that he easily accepts adaptation (which, ironically, is a result of natural selection), but refuses to accept the full theory; all this because he didn’t see it happen.

Before returning to Italy with Galileo, let’s first revisit this statement by Bacon. Here it is in full:

We must not imagine or invent, but discover the acts and properties of nature.

This statement is somewhat paradoxical because it does indeed take us two steps forward, but it also takes us one step back. Two steps forward because it abandons traditional authorities (which is a good thing); one step back because it sets up a new authority, namely, our senses. Wait, our senses can be an authority? No, but that’s what they became under many early thinkers. This kind of reasoning is what legitimized the flat earth theory for so long. For example, if you had a time machine and traveled back in time to the 14th century and asked any number of people why they thought the earth was flat, perplexed, they would answer with their own question: “does it look curved?”

Quick but critical digression: the “white swan” proposition mentioned above comes from the 19th century philosopher John Stuart Mill in his book A System of Logic. In it, Mill points out the major flaw in the Baconian method; the fact that it will never be able to give us certainty:

To Europeans, not many years ago, the proposition, all swans are white, appeared an equally unequivocal instance of uniformity in the course of nature. Further experience has proved to both that they were mistaken; but they had to wait fifty centuries for this experience. During that long time, mankind believed in a uniformity of the course of nature where no such uniformity really existed.

This is an extremely important finding in the study of knowledge. It was first noticed by the Ancient Greek skeptical philosophers but took nearly two thousand more years before being neatly articulated by the Scottish philosopher David Hume in his book A Treatise of Human Nature. “We suppose, but are never able to prove, that there must be a resemblance betwixt those objects, of which we have had experience, and those which lie beyond the reach of our discovery.” No matter how many white swans you may come across in your life, there’s always the possibility that a black swan might be sitting on an undiscovered island in the middle of the ocean. 

David Hume by Allan Ramsay, 1766

Now that we have some context surrounding our “senses as an authority” problem, let’s reexamine Galileo and his Venus observations. In his book, Galileo: Watcher of the Skies, historian David Wootton describes a letter Johannes Kepler received from Galileo in 1597 in which “he made a most remarkable claim.” After revealing he had been a Copernican for quite a while, Galileo writes of the heliocentric theory, “with this hypothesis [I] have been able to explain many natural phenomena, which under the current hypothesis remain unexplainable.” This conflict of theories was a problem, but as Karl Popper writes, “the natural as well as the social sciences always start from problems…” He continues, “seeing a new problem may well be the most difficult step in creating a new theory.” I take this as Popper indicating how much of a gift finding a problem truly is. When we find a problem we should cherish it. From the same book, All Life Is Problem Solving, Popper outlines the growth of knowledge as follows: 

1. The starting point is always a problem or a problem situation.

2. Attempted solutions then follow. These consist of theories, and these theories, being trials, are very often wrong: they are and always will be hypotheses or conjectures.

3. In science, too, we learn by eliminating our mistakes, by eliminating our false theories.

Sir Karl Popper in the 1980s.

In short, all knowledge creation is through trial and error. More specifically, trial and the elimination of error, always with the understanding that we can never be certain that we’ve landed on the truth. We proceed not with certain knowledge, but with good explanations. What are those? Here, the theoretical physicist David Deutsch provides a helpful addendum to Popper’s work with a definition from his book The Beginning of Infinity: a good explanation is “an explanation that is hard to vary while still accounting for what it purports to account for.” Put differently, “God did it” is a bad explanation because it can be used to describe anything.

Given this, what really happened with Galileo and his telescope? As previously noted, he started with a problem; a conflict between two theories. Notice that Galileo already had a theory in mind before he made his observation:; the Copernican theory. This will always be the case. “There is no such thing as ‘raw’ experience,” writes Deutsch; “all our experience of the world comes through layers of conscious and unconscious interpretation.” Or as Popper is supposed to have said, “all observation is theory-laden.”

The predominant theory of Galileo’s time was geocentrism, put forth by the 2nd century astronomer Claudius Ptolemy, asserting that the Sun, the Moon, and the stars all circle the earth. Ptolemy’s was a complex model involving different epicycles. He came to this mistaken hypothesis by the false authority of his senses—by looking at the movement of the heavens and attempting to describe what he saw. Galileo on the other hand observed Venus (a wondering dot in the sky conjectured to be a planet) with having both the Ptolemaic and the Copernican theories in mind. Long story short, the Copernican theory simply made more sense than the common-sense theory put forth by Ptolemy. But as Deutsch notes in The Fabric of Reality, “our best theories are not only truer than common sense, they make more sense than common sense.” Common sense is just another way of describing the Baconian method.

Pages from 1550 Annotazione on Sacrobosco's De sphaera mundi, showing the Ptolemaic system.

This brings us back to Darwin. How did he come up with the theory of evolution by natural selection? He did exactly what Bacon said not to do, he imagined and invented! As with the creation of all knowledge, he didn’t start with an observation, but with a problem. What was his problem? It was the “mystery of mysteries,” as he describes it in the Origin, alluding to a phrase first uttered by the naturalist John Herschel, who was referring to precisely the same problem: what is the origin of species? The prevailing theory in Darwin’s day was standard biblical creationism, bracketed by Plato’s essentialism. Darwin himself held this view before encountering a conflict between his theory and his observation. The evolutionary biologist Ernst Mayr describes this conflict in his introduction to Origin’s facsimile:

Three sets of observations, in particular, impressed Darwin: that fossils from South America are related to the living fauna of that continent rather than to contemporaneous fossils from everywhere; that the faunas of the different climatic zones of South America are related to each other, rather than to animals of the same climatic zone on different continents; and, most important, that the faunas of islands (Falkland, Galapagos) are related to those of the nearest mainland and that related species occur on different islands of the same archipelago.

When one is faced with a situation like this—a problem situation—one has to start making guesses as to how to fix it. That’s precisely what Darwin did. He had never seen anything like natural selection before, he simply made a guess. The theory of natural selection didn’t enter his brain through his senses. Rather, it left his brain through his senses. More specifically, it was created between his ears and left through his hands and mouth. Nature doesn’t create laws and impose them on us. Instead, we create laws and apply them to nature. Are these laws true? We can never know for certain. Again, laws fall under knowledge, and all explanatory knowledge is conjectural, a “best” guess as it were. 

And that brings us back to Tucker Carlson, who finished his rant against Darwinism by claiming: “Darwin’s theory is [totally untrue]. That’s why it’s still a theory.” Despite such ignorance, Carlson actually gets something right with this last statement. Natural selection is indeed still a theory and will remain so unless it gets overthrown by a new theory, a better theory. If this were to happen, the new theory would also remain just a theory—perennially tentative and subject to revision based on new information or analyses.

In his book The Greatest Show On Earth, Richard Dawkins takes great pains to combat the “just a theory” claim. In order to do so, he fights tooth and nail the very philosophy I’ve been speaking of this whole time: “As for the claim that evolution has never been ‘proved’, proof is a notion that scientists have been intimidated into mistrusting. Influential philosophers tell us we can’t prove anything in science.” Nevertheless, Dawkins lands the philosophical plane: “The more energetically and thoroughly you try to disprove a theory, if it survives the assault, the more closely it approaches what common sense happily calls a fact.” That said, to reiterate, knowledge can never be certain. Popper explains it like this:

The empirical basis of objective science has thus nothing “absolute” about it. Science does not rest upon rock-bottom. The bold structure of its theories rises, as it were, above a swamp. It is like a building erected on piles. The piles are driven down from above into the swamp, but not down to any natural or “given” base; and when we cease our attempts to drive our piles into a deeper layer, it is not because we have reached firm ground. We simply stop when we are satisfied that they are firm enough to carry the structure, at least for the time being.

My guess is that thinkers such as Newton, Galileo, Descartes, Leibnitz, Hume, and Aristotle—the thinkers mentioned by Dawkins above—didn’t land on natural selection because of its abstract nature. The common sense of their day was far too strong to overthrow. They were afraid to step into the land of best guesses where the only thing that matters is the falsifiability of a theory (that is, it can be put to some test and shown to be wrong), not its verifiability (simply finding more cases where it appears to hold true). It’s not surprising that Darwin sat on his “dangerous” idea for so long before publishing. Its sheer boldness is breathtaking. And it is only through such boldness that makes science progress—by testing bold and seemingly improbable ideas.