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Sir Karl Popper: An Interesting Philosopher

December 09, 2018     Time: 30:06
Sir Karl Popper: An Interesting Philosopher


Dr. Craig discusses some of the contributions of philosopher Karl Popper.

KEVIN HARRIS: Bill, this is a very entertaining article on the late, great Karl Popper. We’ve talked a lot about Sir Karl Popper from time to time on our podcast. As a way of introduction, what do you know of Karl Popper? What have you read?

DR. CRAIG: Oh, I am not at all a “Popperian” expert. I’ve read a little bit in his work in the philosophy of science and the falsification principle. But since he and I are working in very different fields of philosophy, there has not been much intersection of our work.

KEVIN HARRIS: He is best know for that principle of falsification which we will get into here in just a moment. He died in 1994. Scientific American just republished an interview[1] conducted with him by John Horgan when Sir Popper was 90 or 91 years old and just still sharp as a tack, and very funny! There's some funny things in here. One of them is,

Popper’s falsification principle has been used to attack string and multiverse theories, which cannot be empirically tested. Defenders of strings and multiverses deride critics as “Popperazzi.”

[laughter] Using Karl Popper's principle of falsification, again, that we'll get into here in just a moment. But he had the audacity to ask him, as we begin this interview, if his principle of falsification can be falsified. I can't believe he had the guts to ask him that, but he does. In the middle of page two he says,

I noted that in his writings he seemed to abhor the notion of absolute truths. “No no!” Popper replied, shaking his head. He, like the logical positivists before him, believed that a scientific theory can be “absolutely” true. In fact, he had “no doubt” that some current theories are true (although he refused to say which ones). But he rejected the positivist belief that we can ever know that a theory is true. “We must distinguish between truth, which is objective and absolute, and certainty, which is subjective.”

DR. CRAIG: That's a critical distinction, isn't it? Truth is objective and absolute in the sense that it is person-independent. It is the way reality is whether anyone apprehends it or not. Whereas certainty is a psychological state. It is a subjective state of mind. You can be certain about things that turn out to be false, and you can be doubtful about things that turn out to be true. But while it is, I think, so important to distinguish between truth and a certainty, what I'm troubled by is that Popper seems to equate knowledge with certainty. He says he rejects the view that we can ever know that a theory is true. Well, I think what would be correct is that we could never have certainty that a theory is true. Scientific knowledge is always tentative; it could be falsified tomorrow. But I don't think that certainty is a necessary condition of knowledge. And he himself says in the interview on the next page, “scientific certainty doesn't exist.” Science is not a field of study where we arrive at certainty. But we have scientific knowledge. For example, the theory of blood circulation in the body pumping by the heart may not be certain but surely we know that. So this equation of knowledge with certainty is, I think, a false equation, and it is one that is very, very widespread in our culture where people will say things like you can't know that God exists, you can't know that Christianity is true, or you can't know that the universe began to exist. What they mean by that is that you don't have certainty of those things. That is a false equation.

KEVIN HARRIS: We may have lost a few listeners on logical positivism. Do you want to go back over that?

DR. CRAIG: Positivism was a school of thinking during the 1930s and 40s that was deeply anti-metaphysical in its character. It thought that if a question does not have a scientific answer then it wasn't a real question. It was just a pseudo-question masquerading as a question. So the positivists sought to cleanse philosophy of metaphysics, ethics, aesthetics, anything that wasn't reducible to science. One of the principal tools that the positivist used was their verification principle of meaning. What this stated was that if a sentence cannot be scientifically verified then the sentence was meaningless. It was not a statement of fact at all; it would simply be an expression of the speaker's emotions or sentiments. This verification principle soon succumbed to criticism and was replaced by the falsification principle which said that if a sentence cannot be falsified then it's meaningless. It agreed that there can be sentences that are meaningful even though you can't verify them. As the article explains, Popper thought that no scientific theory can be verified (can be proven true), but he thought they could be falsified by decisive experiments. So the suggestion was that in order to be meaningful a sentence needs to be falsifiable. Now, that's not what Popper means, I think. This interview makes it very clear. But that's the way it was employed by these logical positivists at the time. This principle also soon went by the board. So the most important philosophical event of the 20th century was the collapse of this positivism and verification principle of meaning which resulted in a resurgence of metaphysics in philosophy which was then also attended by a renaissance of Christian philosophy. We are the heirs of this renaissance of Christian philosophy which resulted from the collapse of positivism.

KEVIN HARRIS: From what I've read, it was a battle. In the 40s and 50s, if you weren't a logical positivist you would fight tooth and nail with them. I read that C. S. Lewis felt like he did not do well against a logical positive who encountered him one time.

DR. CRAIG: Lewis at Oxford was living and working during the heyday of positivism in the UK as well as in the United States. It is very interesting to read the ways in which Lewis tried to combat this false philosophy. He saw its errors and sought to do his best to try to counteract it.

KEVIN HARRIS: I wonder if a modern-day example would be the way that we have to encounter scientism.

DR. CRAIG: Scientism is the long shadow of positivism. The attitudes of people like Stephen Hawking, Lawrence Krauss, Richard Dawkins, and others is the lingering shadow of this positivistic attitude that anything that cannot be scientifically settled is just a pseudo-question, not even worth talking about.

KEVIN HARRIS: The article continues,

Popper disagreed with the positivist view that science can be reduced to a formal, logical system or method. A scientific theory is an invention, an act of creation, based more upon a scientist's intuition than upon pre-existing empirical data. “The history of science is everywhere speculative,” Popper said. “It is a marvelous history. It makes you proud to be a human being.” Framing his face in his outstretched hands, Popper intoned, “I believe in the human mind.”

DR. CRAIG: He was emphasizing here the creativity of the individual scientist in coming up with his models of reality. He rejected the hypothetico-deductive model of scientific explanation that was dominant at the time.


For similar reasons, Popper opposed determinism, which he saw as antithetical to human creativity and freedom. “Determinism means that if you have sufficient knowledge of chemistry and physics, you can predict what Mozart will write tomorrow,” he said. “Now this is a ridiculous hypothesis.” Popper realized long before modern chaos theorists that not only quantum systems but even classical, Newtonian ones are unpredictable. Waving at the lawn outside the window he said, “There is chaos in every grass.”

What do you think about that?

DR. CRAIG: I think that appealing to our ignorance of the behavior quantum systems and chaotic systems is not sufficient for a rejection of determinism. All that shows is that we do not have sufficient knowledge to be able to predict the outcome of these systems. But the claim of determinism, as he says here, is that if you did have sufficient knowledge of chemistry and physics you could predict what Mozart would write. I agree with him in rejecting that. That kind of determinism, that denial of free will, is incorrect, but I wouldn't appeal to the kind of indeterminacy in quantum physics and chaos theory to ground that. Even a determinist like Lawrence Krauss, for example, in our dialogue in Australia, would say we might as well act as if we have free will because it's so complex that we can't predict what's going to happen in the future. Do you see the difference? He didn't believe in free will, he thinks everything is determined, but he recognizes that these systems are simply so complex that it's impossible to predict what's going to happen. But that doesn't secure freedom.

KEVIN HARRIS: Another noble lie that we have to believe?

DR. CRAIG: Yeah, act as though you were free even though you know that you are not. That’s his advice.

KEVIN HARRIS: I love this sentence here. In other words, there's an additional something that Mozart had that produced his work that physics, science, math, and all that cannot get to. Chemistry and physics and freedom of the will. You can't predict what Mozart would write by physics and math alone.

DR. CRAIG: Because there's genuine creativity and spontaneity.

KEVIN HARRIS: This is funny here. He says,

Popper was proud of his strained relationship with his fellow philosophers, including Wittgenstein, with whom he had a run-in in 1946. Popper was lecturing at Cambridge when Wittgenstein interrupted to proclaim the “nonexistence of philosophical problems.” Popper disagreed, saying there were many such problems, such as establishing a basis for moral rules. Wittgenstein, who was sitting beside a fireplace toying with a poker, thrust it at Popper, demanding, “Give me an example of a moral rule!” Popper replied, “Not to threaten visiting lecturers with pokers,” and Wittgenstein stormed out of the room. [For other accounts of this famous episode, see the book Wittgenstein’s Poker.]

Wittgenstein said, If I have exhausted the justifications I have reached bedrock and my spade is turned. In other words, you can't turn it again. You've hit the bedrock. Then I'm inclined to say this is simply what I do. I've heard many times of Wittgenstein's spade but never of his poker. That's what's funny about this book.

DR. CRAIG: That would be an expression of foundationalism – that you reached the foundations of knowledge below which you cannot dig.

KEVIN HARRIS: He gets into postmodernism next in this interview. He says,

Popper abhorred philosophers who argue that scientists adhere to theories for cultural and political rather than rational reasons. Such philosophers resent being viewed as inferior to genuine scientists and are trying to “change their status in the pecking order.” Popper was particularly contemptuous of postmodernists who argued that “knowledge” is just a weapon wielded by people struggling for power. “I don't read them,” Popper said, waving his hand as if at a bad odor. He added, “I once met Foucault.”

What's he talking about here?

DR. CRAIG: He's talking about the postmodernist claim that knowledge is simply a weapon utilized by those who want to gain political power and influence. There isn't really any objective truth to be arrived at. Knowledge is simply one way in which the powerful exploit the underclasses and maintain their control over them. And Popper rightly rejects this sort of postmodernist attitude.


Popper then proceeded to talk about it. “Scientists are not as self-critical as they should be,” he asserted. “There is a certain wish that you, people like you” – he jabbed a finger at me—“should bring them before the public.” He stared at me a moment, then reminded me that he had not sought this interview. “Far from it,” he said. Popper then plunged into a technical critique of the big bang theory. “It's always the same,” he summed up. “The difficulties are underrated. It is presented in a spirit as if this all has scientific certainty, but scientific certainty doesn't exist.”

Wow! Here's a philosopher of science who is saying that.

DR. CRAIG: And that's quite right as I indicated earlier in our podcast. Science is not a field of inquiry at which you arrive at certainty because the results are always tentative.


I asked Popper if he felt biologists are also too committed to Darwin's theory of natural selection; in the past he had suggested that the theory is tautological and thus pseudo-scientific.

DR. CRAIG: Here Horgan is really pressing the envelope. He's going after the sacred cow of evolutionary biology and asking Popper, Is this also an area in which scientists are not sufficiently self-critical?

KEVIN HARRIS: I remember Philip Johnson writing that natural selection is a tautology.

DR. CRAIG: And that was the suggestion that Popper had said, too. When you say “the fittest survive” or “only the fittest survive” how do you define the fittest? It's those that survive. So it was circular. Now, here he walks that back a bit.


“That was perhaps going too far,” Popper said, waving his hand dismissively. “I'm not dogmatic about my own views.” Suddenly he pounded the table and exclaimed, “One ought to look for alternative theories!”

DR. CRAIG: Yes. What's interesting about this is that most of our listeners, and I'm sure most of the American public, would be unaware that the so-called modern neo-Darwinian synthesis has, in fact, collapsed among evolutionary biologists. It has traditionally been said that biological complexity is explicable in terms of the twin mechanisms of random mutation and natural selection. That view now is largely rejected among evolutionary biologists. They have discovered that those are not the only mechanisms that drive evolutionary change forward, and that other sorts of mechanisms need to be taken into account. So the kind of self-critical attitude that Popper expresses does need to be exercised even with regard to these sacred cows like neo-Darwinian evolutionary theory. There is no new consensus to replaced it. The field is currently in turmoil.

KEVIN HARRIS: “Popper scoffed at scientists’ hope that they can achieve a final theory of nature.” I wonder if this is the TOE – the theory of everything.

DR. CRAIG: Yes, this would be your sort of final theory of nature that would incorporate all of the four fundamental forces of nature. Yes.


“I must show you one passage that bears on this.” He shuffled off and returned with his book Conjectures and Refutations. Opening it, he read his own words with reverence: “In our infinite ignorance we are all equal.”

DR. CRAIG: This is an interesting point because some cosmologists like George Ellis have argued that in order to arrive at a theory that would enable us to unify gravitation with all of the other fundamental forces of nature we would have to have energy so high that it would require a nuclear reactor the size of the earth to achieve, and we'll never be able to do that. So Ellis thinks that we may well have reached the sort of limits of our knowledge with respect to a fundamental theory of nature because we simply can't get the energies that would be required to understand how these forces would be united together.

KEVIN HARRIS: That boggles my mind. The interviewer, John Horgan, says,

I decided to launch my big question: Is his falsification concept falsifiable? Popper glared at me. Then his expression softened, and he placed his hand on mine. “I don't want to hurt you,” he said gently, “but it is a silly question.” Peering searchingly into my eyes, he asked if one of his critics had persuaded me to pose the question. Yes, I lied. “Exactly,” he said, looking pleased.

“The first thing you do in a philosophy seminar when somebody proposes an idea is to say it doesn’t satisfy its own criteria. It is one of the most idiotic criticisms one can imagine!” His falsification concept, he said, is a criterion for distinguishing between empirical and non-empirical modes of knowledge.

DR. CRAIG: Let's stop right there. This is a critical sentence. One of the reasons that the verification principle succumbed to criticism was precisely this problem of self-defeat. It is self-referentially incoherent. If you say only claims that are empirically verifiable are meaningful, it is perfectly legitimate to say, “Is that claim empirically verifiable?” And the answer would be, no. There's no amount of empirical evidence that could verify it. Therefore, the verification principle is meaningless, and therefore self-defeating. And that is not a silly criticism. That is devastating to this claim. If the falsification principal were that sort of principal, if one is saying, a sentence in order to be meaningful must be falsifiable, it would be perfectly legitimate to say, is that claim falsifiable? And if it's not, then it's meaningless. But here Popper escapes self-defeat by reframing what falsification is. It's not a criterion of meaning for Popper. What he's saying is that any empirical mode of knowledge needs to be falsifiable. If a mode of knowledge is non-falsifiable then that's a non-empirical mode of knowing, and that's unproblematic. That's just saying there are different modes of knowing. Some are empirical, some are non-empirical, and the empirical ones are those that are falsifiable through scientific experiment. Unproblematic. It's ambivalent here. He does say that the first thing you do in the philosophy seminar is ask, Is this thing self-defeating? And he says that's an idiotic criticism. It's not idiotic with regard to certain sorts of claims where they would apply to themselves. But he does enunciate the concept of falsification in such a way that it's immune to that criticism. It isn't self-defeating. He goes on to say, in fact (look at the next sentence): falsification itself is “decidedly unempirical.” Falsification would be a non-empirical notion. “It belongs not to science but to philosophy, or ‘meta-science,’ and it does not even apply to all of science.” So he's simply distinguishing between empirical and non-empirical modes of knowing. And he says that falsification itself doesn't belong to the empirical way of knowing.

KEVIN HARRIS: Horgan says,

Popper seemed to be admitting that his critics were right: falsification is a mere guideline, a rule of thumb, sometimes helpful, sometimes not.

DR. CRAIG: Yes, and particularly here in the sentence “it does not even apply to all of science.” There are aspects of science that are also non-falsifiable. We've talked about this in other venues. Science is filled with claims that cannot be empirically falsified or verified. A great example would be in the special theory of relativity. The claim that the one-way speed of light is constant is unfalsifiable because we can only measure the round-trip velocity of light. You can send a light signal out and then have it bounce back from a mirror or something to the source and measure the round-trip velocity – how long did it take for the light signal to go out and come back? And that is constant. The light signal always travels at the same velocity in a round-trip. But we can't measure the one-way velocity of light. Theoretically, it's possible that light goes out at one velocity and then comes back at a different one, and we'd never be able to tell. And yet obviously this is part of a scientific theory that's part of the foundations of physics today. And there are many other principles of that sort. So Popper is quite right here in saying that falsification doesn't even apply to all of science.

KEVIN HARRIS: Where this hits home is that so many of us listening right now know about the principle of falsification because it's been used against us in debates and in times of discussing our faith saying there's no way you could falsify God.

DR. CRAIG: Exactly. Just earlier today, Kevin, you and I were reading a blog by a humanist in which he was indicting Christianity and the views I've defended because of their unfalsifiability. I think Popper’s interview here is so helpful in just exploding the misunderstandings that are underlying that sort of criticism.

KEVIN HARRIS: The interview continues. He says,

Since Popper seemed so agreeable, I mentioned that one of his former students had accused him of not tolerating criticism of his own ideas. Popper's eyes blazed. “It is completely untrue! I was happy when I got criticism! Of course, not when I would answer the criticism, like I have answered it when you gave it to me, and the person would still go on with it. That is the thing which I found uninteresting and would not tolerate.” In that case, Popper would throw the student out of his class.

DR. CRAIG: I could sympathize with him here. I've been in dialogues with people sometimes where they say, I just can't see how blah, blah, blah. And then you answer it and explain it to them, and then the way they respond is to say, Yeah, but I just can't see how blah, blah, blah. And you think, Didn't they listen to what I’ve just said? Many times people don't know how to advance the conversation. All they do is repeat the argument that they originally gave and don't understand that it's been answered. Now, I've never thrown a student out of class as Popper did! But I can understand his frustration when you try to answer a question and the questioner simply repeats what he'd already said.

KEVIN HARRIS: It's got to be the frustration of every professor and every teacher. He says,

I slipped in a final question: Why in his autobiography did Popper say that he is the happiest philosopher he knows? “Most philosophers are really deeply depressed,” he replied, “because they can’t produce anything worthwhile.” . . . “It would be better not to write that,” he said to me. “I have enough enemies, and I better not answer them in this way.” He stewed a moment and added, “But it is so.”

Philosophers being depressed, huh?

DR. CRAIG: Yes, isn't that an interesting observation? All I can say is that I am a very happy philosopher and well-adjusted!


When Popper died two years later [he died in the mid-1990s], the Economist hailed him as having been “the best-known and most widely read of living philosophers.” But the obituary noted that Popper’s treatment of induction, the basis of his falsification scheme, had been rejected by later philosophers. “According to his own theories, Popper should have welcomed this fact,” the Economist noted, “but he could not bring himself to do so. The irony is that, here, Popper could not admit he was wrong.”

But he did admit he was wrong. I mean, he didn't admit he was wrong; he clarified if he's talking about falsification.

DR. CRAIG: Well, the question there is – we haven't talked about it so much – of his view of induction. Remember he didn't think that scientific theories could be verified; they could only be falsified. I would say the vast majority of thinkers today would say of course a scientific theory can be verified by the evidence. I think that they would be right in saying that. That doesn't mean that it can be known to be true with certainty but then, as Popper himself realized, scientific certainty is impossible.[2]


[2]           Total Running Time: 30:06 (Copyright © 2018 William Lane Craig)