Chapter 1.4: Karl Popper and the logic of falsification 

Thank you, Jesus.

These videos are one of the reasons that I love the internet. Free college lectures to continue my education.

Lots of comments on this video, including some critical ones. Can't respond to everyone individually -- and sometimes the criticism is a bit amorphous -- but let me give an overall response and provide a link to a more in-depth engagement with Popper at the end. Now, first of all, this is a short introductory lecture. I'm in complete agreement with anyone making the point that much more could be said about this issue; that we could delve into Popper's overall story about induction, his notion of corroboration, his ideas about observation, and so on. But -- and this is crucial from the perspective of education -- none of that would change the basic point made by the video. In philosophy of science, it is not at all controversial to state that Popper's attempt to do without induction is, in the end, a failure. It is a failure for multiple reasons, but in part because of the reliance on inductively established beliefs in the performance and interpretation of any experiment. So, yes, Popper would have a lot to say about my video. But, no, it would not substantially change the outcome. And this is not a private opinion of mine, but a widely held judgement among philosophers. Now some of the people who left comments on this video suggest that philosophers in general have misunderstood Popper. This is a myth, a myth that has been created and popularised by Popper himself. I'll just quote from his text Science: Conjectures and Refutations: "Criticism of my alleged views was widespread and highly successful. I have yet to meet a criticism of my views." Or again, from the first page of Objective Knowledge: "[...] those works which take notice of my ideas usually ascribe views to me which I never held, or criticize me on the basis of straightforward misunderstandings or misreadings, or with invalid arguments." However, Popper's views on induction have been criticised by some of the best philosophers of science of the 20th century, and if you read them side-by-side with Popper, it's clear that they have perfectly understood him. I especially recommend Wesley Salmon's "Rational Prediction" and Hilary Putnam's "The 'Corroboration' of Theories" if you want a taste of this literature. Unfortunately, Popper often writes in a way that hides the more problematic aspects of his views under ambiguities and ambivalences, while at the same time positing straw man positions as his enemy. If you want to learn more about Popper and see an in-depth analysis of one of his most famous and hugely problematic texts, I recommend that you check out the series I did on my own channel about Science: Conjectures and Refutations. ru-vid.com/group/PL8Nxd4OXpzqlbV-ZBu4VfKHRtThzEL7Pf

The speaker has misunderstood Popper. Popper was not speaking about practice, he was speaking about epistemology. He recognised that in many cases individuals in practice were not performing science as he described it, but that he was making clear how knowledge was being acquired. Freud for instance did not conduct science as Popper described it, but he also did not acquire much knowledge via his attempts to only affirm his theories that were highly variable. Popper also recognised that there were many underlying theories regarding measurement involved in every attempt to falsify. I suggest that those who want to understand Karl Popper not turn to this video (which is confused), but rather read Oxford Physicist David Deutsch, who has clearly expressed Popperian science in his book: The Beginning of Infinity.

The complications critique misses a more relaxed requirement that a hypothesis be at least falsifiable in theory to satisfy Popper. Obviously complications can confound a given instance of an observation. But these are two different thresholds. So Popper holds.

Respectfully, I believe that you have a mistaken conception of falsification. Induction is not inherently antithetical to falsification. The only requirement is that premises with an inductive structure are tested deductively. That test is the search for observational data that either establishes modus tolens or discovers a counter-example(s). Take for instance an inductive premise like [all swans are white.] It has an inductive structure because we are incapable of observing all swans, but in all of those cases we have observed swans - they have been white. This inductive conclusion could be starting place in the process of falsification. How do we proceed deductively? Look for cases in which we have a swan, but not white. We find a counter-example in Australia: black swan. Hence, the inductive conclusion has been proven false. However, let's say we take the inductive conclusion that all swans are either black or white. So then we decide to search the earth far and wide for five years looking for a counter-example, which could be a pink swan - for example. Alas, we turn up we nothing. What Popper says is that there is reason to believe, now, that the conclusion all swans are either black or white has truth value. Only premises/conclusions/theories which can be proven false, and have stood rigorous attempts at being proven false, are worthy of being considered as truthful. We have now not only all of the positive evidence that supports the conclusion that swans are either black or white, i.e. all the black and white swans we observed. But in addition to that, in the negative sense, we also have all the experiences in which swans that are neither black nor white were not found, which is also evidence. That's falsification. As for the semantics, honesty and precision is key. And honesty goes both ways, both in describing and not purposely misinterpreting the meaning of a theory.

It is amazing how many simply fail to comprehend simple point of Karl Popper. This presenter is no exception. Oh, well, at least he is trying and those more curious will read Popper in the original (multiple times).

“The belief that there is only one truth and that oneself is in possession of it seems to me the root of all the evil that is in the world” ― Max Born (1882-1970)

so clearly and simply presented, thanks! greetings from Poland ;) !

Your videos helped me prepare for my exam! Thanks

You are missing the entire idea of iterative scientific process. All those supposed hidden assumptions are in fact included in the theory or in the rest of Popper philosophy you failed to explain. If the language of the theory is too vague to falsify, then the theory is unfalsifiable and need to be replaced with more precise formulation and falsification is attempted again. This process never ends. What is falsifiable and what is not depends on current state of the theory. If you are an amateur who don't know how freezers work then this naive theory can be considered falsifiable and Popper's prescribed methodology will in fact lead you to discover that freezers need electricity and other valuable information. If you are a professional scientist then you are somewhere else and need to use more precise language to squeeze out something new, but in that case these supposed hidden assumptions you are taking about are included in this more precise theory. They are not coming from induction but from previous iterations of scientific process. Theory converges towards something, which approximates truth, but we can never say we know the truth.

This helped so so much. I have to write a philosophy essay on this topic and I just could not get a grasp on it. THANK YOU

could you please provide us with the references of the information mentioned in this video?

I'm no philosopher, so take what I say with a grain of salt, but it seems to me the speaker is incorrect in his idea that the frog theory makes assumptions. In the three examples he gave, each of them ended up changing the meaning of the words and over all language. First, to say "all frogs die after a week in the freezer" means that the total continuous time the frogs were in the freezer is one week. It does not at all mean that someone took them out during that one week and put them back before the week was over so that they are still there when you go to remove them at the end of the week and that you assume they had always been there for the whole week. It's not an assumption, its the basic meaning of the words. Secondly, the whole idea that "the freezer is working and it didn't die" is assuming is ridiculous. This is a hypothetical situation. Its not actually being tested in the real world. If it was you would make sure the freezer is working the entire time. If for any reason it breaks down, you would stop the experiment, fix or replace the freezer, then restart your experiment. Lastly, assuming the frog is a frog and not a toad is the same problem as in my first point. Its a case of changing the meaning of the word. A frog is not a toad. Granted, a lay person might misuse it to mean any four legged amphibian that similarly resembles a frog which might include toads, but regardless when someone says frog, most everyone who knows English thinks of the same creature. So I would say the speaker is just nitpicking to try and support his argument. I'm a nobody and have never even heard of this Popper guy until just now but even I'm pretty sure he knew what he was talking about and the speaker in this video does not.

On the pont that popper is wrong because there are scientists claiming to know stuff. My interpretation of Popper is that he was not interested in describing how the average or how the worst scientist does science. But rather how science works at its best and how we should do science.

Popper certainly did not claim that scientists only use deduction

A theory should predict the results of a reasonable experiment. ISSUE. Who defines REASONABLE?

I enjoyed this very much.

But isn't falsificationism still useful, given main variables known and estable? E.g. If all the frogs have the same -or, at least, main- characteristics, then the falsification may be correctly applied with an equal frog. And, therefore, inductionism and falsificationism would be mutually complementary (and Popper got wrong only for considering them mutually exclusionary).

The statement that all scientists use deduction is not deductive...

you described naive falsificationism which is not popper's theory

im loving this stuff, i thought he was going to do in the direction of saying if scientists are only interested in falsification then he would have to spend his entire life acquiring every frog in existence and putting them all in the freezer for a week until he either dies or there are no more living frogs on earth, but his way was much better

The point being made by the video, whether falsification is induction or deduction might be interesting to some but it's not what is important. Popper's method of honing theory through falsification and his idea that theories that can't be falsified aren't precise is also important. Philosophers sometimes miss the point.

Isn't this a rather inflexible version of falsification? I see what you're getting at, and it's important to be aware of inductive reasoning, but one must imagine that Popper is aware that at a certain level, you will rely on inductive reasoning. Otherwise you're just being unproductive and wasting time. I'm fairly new to this, but I find it difficult to believe that he meant his ideology to be used in such a broad and unspecific manner. As with most things, there's obviously a balance if you seek to do reliable science, and this video feels as if it's ignoring that.

Can we use logic to prove or challenge God existence?

Dank je wel!!!!! Geweldig.

With induction you don’t get absolute certainty; the quality of the idea or model or theory depends on the quality of the observations and analysis. which in many ways depends upon what the observer thinks is true. It can often be regressive. Models need adjustments or fine tuning.

Can someone just explain to me the disadvantage of karl popper's theory ??? My English isn't good enough..

Good work

I was in Leiden last summer. Beautiful city!

Anyone who listen to this, please know that this video misrepresents Popper. No one denies that experiments contribute to our knowledge of the world. It increases our confidence in assumptions that are needed in tests and in the tested laws themselves. This experimental process that leads to an increased confidence in laws is what Charles Sanders Peirce called induction. Popper did not deny the existence of this process, but he called it quasi-induction. He understood, as Peirce did, Hume's point that our confidence in our currently accepted laws cannot be explained by deductive logic and observations alone. Something else is needed. This is much related to the debate between the rationalists and empiricists in the 17e and 18e centuries. In this debate, "rationalism" does not mean the use of deductive logic alone. On the contrary, the sufficiency of deductive logic and observations is the claim of empiricism. Rationalists consider that knowledge beyond deductive logic that does not come from observations can nevertheless be valid and is needed to explain science. Hume tried to defend empiricism, but saw the serious problem of induction. With Kant, rationalism came to the rescue in the form of a priori knowledge. However, with the advent of General Relativity and Quantum Mechanics, it became clear that Kant has been misguided by his wrong belief in the certainty of Newton's theory of gravitation. People in the Vienna Circle tried to restore empiricism, but Hume's problem of induction was still there and there was also the Duhem thesis. It did not work. Popper's solution was to accept a form of rationalism. Kant's notion of a priori was fine for Popper, as long as it did not come with certainty. It had to be fallible. In fact, it could come in the form of biological expectations and predispositions. Because the conjectures can be wrong, confrontation with experiments is crucial in Popper's view. What's very wrong in the video is that Popper is depicted as someone who thought that empirical falsifications could be conclusive and sufficient, which is absurd. Popper was, of course, very much aware of the problematic. The rational side, for Popper, includes the use of deductive logic to propose new empirical tests from existing conjectures, but it also include the making of new conjectures inspired by the outcomes of these tests. Because of Hume's problem, the making of conjecture is not rigorous in a logical sense: it is fallible. Popper, of course, knew that. The empirical part is the execution of the empirical tests and their analysis. Because of the Duhem thesis, this part is also fallible. Again, of course, Popper knew that. This video is so wrong. It's a straw man argument.

Did the frog have a sweater on?

6:22 “All observations are theory-laden”, means you need a theory before any kind of observation is performed. And a single test of theory T is only relevant in the context of rival theory R predicting a different outcome, but to get to this crucial test, the new theory T must be a better explanation than its rival R, or else theory T is discarded. In other words, the new theory T must be able to explain the successes of its predecessor R and why, arguably, it is expected to fail in explaining the phenomena in question. Your frog example, although realist, seems to me lacking any explanatory power or for that matter, it also lacks a problem to be solved. I mean, if the problem is merely a nonsensical curiosity, than the example is unproductive for the purpose of thinking about epistemology. Popper’s broader conception of knowledge creation starts off in the light of a problem that seems interesting to solve. The next step is conjecturing a solution followed by its criticism. Popper is right, as a scientist I wouldn’t attempt publication of any scientific result before refuting every criticism I could think of. For the purpose of understanding Popper’s epistemology via thought experiments, remember that scientific theories are only approximated by propositions (such as “all frogs die…”), but they are precisely explanations. In your example, there is only prediction, and prediction without explanation is prophecy. I criticise Popper’s lack of explanation of how creativity works in formulating interesting problems and how it works in coming up with a conjecture. I guess that’s why he said “…there is no such thing as a scientific method.” And by the way, “induction is physically impossible” is a pre-socratic result, neither Hume’s or Popper’s. Newton and Darwin made a mistake when they wrote they used induction. They lived when the tradition of rational criticism was a novelty and they were afraid of being ridiculed if they just told the truth about guesswork. And rightly so, critics would surly have associated them to the tradition of authoritative knowledge they were rebelling against.

is he spewing freshmen's epistemology chapter on Popper (right after Vienna Circle Positivism, right before Kuhn) tier summary, or does he really believe the narrative being told: i.e. what popper held, the bias towards only looking at his 30s work vs. taking some of all his subsequent work on epistemology, mostly concerned with responding to criticism and clarifying misunderstandings of his propositions.

Thankyou Buddha

I have to say, as a student of philosophy it’s a bit strange for me to see the way scientists use formal logic. I don’t see why I couldn’t just observe the freezer for a week, and if everything is honest, then we see our result unfold without any bias. I can’t stay awake for more than 15 hours or so a day, but I can hire someone, who if is honest, can observe while I sleep. If he’s dishonest then nothing about the experiment matters. It’s wasted. What’s wrong with that? _____ I also want to point out that the premise of this argument itself contains an if then statement, which is fine, but if we’re going to be checking every detail then you’d also have to make sure the premise’s antecedent was true, and its conclusion true, before going on to check the rest of the argument. It seems as though this is the same as the ‘more complicated background theory.’ Though Zi can’t believe that’s what science calls a theory. To me that’s just checking your premises! But there’s a problem. On its own an argument of this form *begs the question* since it assumes its desired conclusion in its premise. If it weren’t for external evidence such reasoning would be doomed to failure prematurely. No philosopher would dare to construct such an argument, regardless of evidence or not, and perhaps this is touching on some of the problems with the reasoning in science to begin with. You can’t just make an argument of the form (P->A)->P and expect it to not be problematic.

Your syllogism is incorrect. It should be: if T is true, then we cannot observe O; we observe O, hence T is false.

There is actually a type of frog that can survive being frozen for a while as they need it to get through the winter where they live. They just thaw again when it's getting warmer and live on their happy frog life.

Yes the blueprint of global. Glad I found this

Wow, I noticed most people left the video at a certain point. Now I see why. Really went off the rails about 2/3rds of the way through.

Love his accent

Could you make a video on Paul Feyerabend, please?

6:18 But as you falsify the theory of Karl popper you proved that karl popper is right

what iss with this guy and freezing frogs in freezers?

Super! Dank u!

I don´t know whether this is the typical way the people outside science do science. Yes, there are many assumptions, but these assumptions are so self-evident that you don´t need to bother. For instance, the freezer must be working, none has taken out the frog and only put it back just prior your re-opening the freezer, etc.

You need to read Popper.

How would it feel to have him in the classroom

In this video of logic i saw no truth tables being used v no refutation trees to show your work? So if we assume your premises to be true and conclusion to be false will we find your argument valid?

You seem to be misrepresenting Poppers claims. If scientists were to NEVER claim that a theory is true we would never get anywhere! Surely this really means that they remain open to their conclusions being challenged by new data. That is something very different and a whole lot less dogmatic. I must add that I agree with the point of view that scientists do use inductive reasoning. You have to leap into the unknown to some degree, as long as you test your theory. And that is why we test our theories. Make a rational hypothesis, then test it!

Can't find 1:3 episode

Thanks a ton!

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Please don't kill frogs

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So inconsistency implies incompleteness.

Great presentation - well done! Every theory, every hypothesis, every thesis… is, by definition, propositional, and therefore, is concerned with truth… And I suspect that every scientist who posits a theory/hypothesis/thesis… does so because he believes and possibly, hopes that it turns out to be true - otherwise, why would he even bother with it in the first place! Deductive reasoning, I submit, is just not possible - since that requires that we are in possession of a standard of Truth that is absolute, immutable, incorrigible… In other words… beyond our grasp! But Truth also has to be knowable, and for that, Truth needs to disclose itself to us - it’s called REVELATION…

But why do you use such gory examples?

You should read popper again

9:41 "should" observe and "must" observe are two different conditions. => theory T is not proven to be false.

7:14 Put another way... *suppose* for instance, that you happened to include in your collection --- unbeknownst to you --- several frogs in that population that have evolved chemical antifreeze properties in their bodies to withstand the last couple decades' more extreme winters.... then your supposition that freezing environments are lethal to frogs may not hold! (How'd I do?)

"If theory is true, we should observe O" Naive falsification. Cf. Creationists who claim "since we observe no dogs evolving into cats, evolution is false"

They only use Deductivism and therefore they don't need any background theories? Give me a break. Why then does he posit that the severity of a test is measured relative to background theories? Furthermore, what are we deducing from? Nothing?

"What if aliens surreptitiously replaced all our brains with cranial matter that makes dead frogs look like living frogs? We can see that Popper's wrong again." Sigh. Philosophy (and Phil of science) just took another gut punch from another sophist.

I would argue that the frogs in the freezer is an abstract absolute and you can't introduce random events like 'the freezer may have turned off.'

OK, it's a clear presentation about Fasification & Science in general. But how to make a bridge between this and what are being doing nowadays with Unsupervised Learning? Is not UL a kind of inductive "knowledge"? And how about not testing 20 or 200 frogs, but all the frogs in the world? How to council this ideas with Big Data?

ご参考まで カール・ポパーのまとめ sententiarum2.blogspot.com/2021/12/Karl-Popper-1902-1994_01583578557.html?m=0

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sepnu pues

0:58

6:10 yes they do

8:00 all those "ifs" are addressed by the Systematic nature of Science, so that is more of a philosophical game than an actual problem in how we do science. Yes, we do rely on theories for every observation , but some philosophers make it sound like it is a bad "thing" or induction is not the best way to acquire knowledge ! Well induction is the best way to acquire knowledge since the method of deduction is nothing more than identifying tautologies. Theories are narratives based on more than one observation which inform our new observations. There is an epistemic connectedness throughout all the levels of our observations and that renders scientific conclusions far more vulnerable to our evaluations thus far more credible than any other non-deductive way.

the example is horri ble like honestly ...is this the best you could come up with ? i mean Jesus.

8:45 - you assume the only way anything can be known (in this example the premises) by using induction and then, surprise surprise, you conclude induction is the way science produces theories. The whole point of Popper's philosophy is that induction is wrong, root and branch. That's not how people make theories. It was beautifully put by David Deutsch: "[people ask]: 'How and why can induction nevertheless somehow be done, yielding justified true beliefs after all, despite being impossible and invalid respectively?' ". As for the rest of the video, Popper explains solutions to all your objections in the rest of his philosophy.

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what are you talking about? you have not given me anything else. give me my precious 9.41.

I simply love this lecture... Thank you...

This guy has an extremely shallow understanding of Popper's theories.

Which means Sigmund is a pseudo scientist!.

Where do the premises for deduction come from? Deduction necessitates and presupposes induction.

So is this just a moral opposition to Popper? You’re not really addressing why his ideas don’t work. You’re just saying you don’t like it. Now here’s some unrelated stuff. I only got about 6 minutes in. Maybe you should front load with evidence not just calling him “problematic”.

Hypothesis, not theory, Science Jesus.

Whoa the Uni got this wrong. Massimo Pigliucci has better info on Popper, demarcation and Pseudo Science.

"Trust the Science."

Being has a tendency to 'return' to clusters ='the nature of solidarity' -a desire for empathy -(Wave)-(yin) and also, Being has a tendency to 'exist' as individuals ='the nature of self-expension' -a desire for breed-(Particle)-(Yang) Likewise, humans have two elements. We must realize that we all have both left and right elements -Solidarity and Self Reliance- No one has only one element. so 'Sum' derived from 'two poles' , (thesis, antithesis, synthesis) To develop intellect and ethics by harmonizing the two, It is good to realize it and balance it properly But A few people polarized the crowd(political partisanship) without balancing themselves. And They stole only the sum, only the synthesis from the triangle composition. Now We all have to get out of this deceptive situation. This is not the time for us to hate each other. We have to track down those who have been manipulating us.

Karl popper Science is the history of corrected mistakes.

I think you got it wrong somewhere else Mr.

This guy makes an inductive argument (appealing to the background theories needed by a premise) to "show" that Karl Popper's claims of deductive falsification are generally false 😂. And this after in a previous video hinting at deduction's agnosticism regarding the truth value of premise propositions! 🤦

I’m more confused than ever, having first watched this video and then read the commentary. Various arguments appear logical but it’s difficult to know what is truly valid for a non-philosopher. It’s like quicksand! Can anyone please point to at least one expert in scientific epistemology that has at least consensus agreement amongst most contemporary scientists, that I can use as a starting point. I had read and basically accepted Popper until I listened to this guy, but the seeds of doubt have been sown.

Not a single quote from Popper in this. Not one. I don't think it's accurate to say Popper says there is no induction in science. It's that falsifiability is a necessary requirement for science, not a sufficient condition proving science has occurred. So if something has no conceivable way of being falsified, it isn't science. The pushback against this seems to me to be based on straw-manning and motivated by people in quantum physics and social sciences whose work can't reach this standard.

Oh, dear. Perhaps it is time to pick another subject - it seems logical.

Experience tell us that 24 frogs on a freezer will die in one week, because that has happens repeatedly on all our previous experimentes, what if one day this does not happen for unknown reason, will we be willing to investigate the new phenomenon? Or will we cover the new discovery to keep the status quo, I find this rather dangerous to silence of any kind, political science, natural science, etc. Karl popper idea was to keep an open mind for new discoveries, new ideas. Looking for the truth is expecting the unexpected, Confirming our dogma involves twisting reality. Truth burns where dogma dies.

I am confused by this. He teaches at a university. I would assume he has been educated and knows how to not mangle an argument. Then he wheels out some idiot called Popper who believed in some very naive stuff. Where did this Popper come from? Can he please do another presentation with a less naive Popper? Students of Leiden, you have my profound sympathies.

why is no one telling that toads are kinds of frogs?

Isnt this a philosophical brain game?

“Suppose some animal lover took the from out of the freezer” So you would have to change the statement. Is this for real? Are you a flat earther??? Please tell me this is a bit.

Your lectures are absolutely excellent, thank you.

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2:30

Your shirt man....