I believe there are no correct, unaddressed criticisms of Karl Popper’s epistemology (Critical Rationalism – CR). If I'm mistaken, I'd like to be told. If others are mistaken, I'd like them to find out and take an interest in CR.

I've found CR criticism falls into some broad categories, with some overlap:

1. The people who heard Popper is wrong secondhand but didn’t read much Popper and have no idea what CR is actually about. They often try to rely on secondary sources to tell them what CR says, but most secondary sources on CR are bad.

2. The pro-induction people who don’t engage with Popper’s ideas, just try to defend induction. They don’t understand Popper’s criticism of induction and focus on their own positive case for induction. They also commonly admit that some criticisms of induction are correct, but still won’t change their minds or start learning the solution to induction’s flaws (CR).

3. The falsificationism straw man, which misinterprets Popper as advocating a simplistic, false view. (There are some other standard myths too, e.g. that Popper was a positivist.)

4. Critics of The Logic of Scientific Discovery who ignore Popper’s later works and don’t engage with CR's best ideas.

5. Critics with points which Popper answered while he was still alive. Most criticisms of Popper are already answered in his books, and if not there then in this collection of Popper criticism and Popper’s replies. (I linked volume two which has Popper’s replies, you will want volume 1 also.)

If you believe Popper is wrong, then: Do you believe you personally understand CR? And have you looked at Popper’s books and replies to his critics to see if your point is already answered? If so, have you written down why Popper is mistaken? If not, do you believe someone else has done all this? (They understand CR, are familiar with Popper’s books including his replies to his critics, and wrote down why Popper is mistaken.)

Whether it’s by you or someone else, you can reply with a reference to where this is publicly written down in English. I will answer it (or refer you to an answer or get a colleague to answer). Here is what I expect in return: if your reference is mistaken, you will study CR. You were wrong about CR’s falsity, so it’s time to learn it. If you would be unwilling to learn CR even if you agree that your referenced criticism of CR is false, then you shouldn’t have an opinion on CR. If you still wouldn’t want to learn CR even if all your objections were wrong, then you either aren’t participating in the field (epistemology) or shouldn’t be. (I have nothing against lay people as long as they are interested in learning and thinking. I do have something against people, whether lay or philosophy professors, who state their opinion that Popper is wrong but would not be willing to learn about Popper even if they found out their negative beliefs about Popper are false.)

If you believe one of the many criticisms of Popper is correct, but you don’t know which one and don’t want to pick one, then you are not treating the matter rationally. It’s unacceptable if your plan is, on having one criticism answered, to simply pick another one, and repeat indefinitely. You’re welcome to have one good reference which makes multiple important points, but you don’t get to just keep referencing different critical authors repetitively (as each one fails, you pick another) while not reconsidering your own beliefs. You need to stick your own neck out – as I do. If I can’t answer a challenge to CR I will reconsider my views.

If you want to bring up a couple criticisms at the start, which are written in different places, but you won't add any more later, then that could be reasonable – but provide a brief explanation of why it's needed. In this case where you want to bring up multiple points by different authors, I'd expect you to be referencing specific sections or short works, not multiple whole books. E.g. you could reasonably say you have 3 criticisms of Popper, chapter 3 of book X, chapter 7 of book Y, and paper Z.

Alternatively, if Popper is mistaken but no one has actually written correct criticism (including you), then how do you know he's mistaken? Maybe he's not!

Note: I'm interested in criticisms like "Popper's idea X is false b/c Y.", not like "I wasn't convinced by Popper's writing on topic X." (The second one is compatible with Popper being correct, and is too vague to answer.)

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Broadly, the reason criticisms of CR fail is the critics do not understand CR. Having read a lot of Popper criticism, I can report this theme is nearly universal in my experience. (There is one problem with CR, which sometimes comes up, which I fixed.) CR is hard to understand because it disagrees with over 2000 years of epistemological tradition. And people in general massively underestimate the effort it takes to understand ideas well. (People seem to think they can read a philosophy book once and understand it, but that isn’t how it works – study and discussion are needed to clear up misunderstandings.) Pointing out misunderstandings of CR, with quotes, is one of the typical ways I answer CR criticisms.

Secondarily, Popper criticism often fails because the critic is much less smart and knowledgeable than Popper (one of the world’s best ever thinkers). I think people can get smarter and more knowledgeable if they make the effort, but most people don’t make that effort in a serious, persistent way and put a ton of time into it. I will not use this as an argument against any particular criticism. It’s not an argument, but it is a part of the world’s intellectual/scholarship situation which I think matters, and it helps explain what’s going on. It’s hard to criticize your intellectual betters, but easy to misunderstand and consequently vilify them. More generally, people tend to be hostile to outliers and sympathize with more conventional and conformist stuff – even though most great new ideas, and great men, are outliers.

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See also: CR reading recommendations.

William W. Bartley on Popper:

Sir Karl Popper is not really a participant in the contemporary professional philosophical dialogue; quite the contrary, he has ruined that dialogue. If he is on the right track, then the majority of professional philosophers the world over have wasted or are wasting their intellectual careers. The gulf between Popper's way of doing philosophy and that of the bulk of contemporary professional philosophers is as great as that between astronomy and astrology. [emphasis added]

I agree with this comment. Note it doesn't apply to Ayn Rand, who is also an outcast from the majority of professional philosophers.

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The quote wording is not exact. I haven't checked the original document. Sources:

Bartley, W. W. (September–December 1976), "III: Biology - evolutionary epistemology", Philosophia, 6 (3–4): 463–494

Cite found here and here. Those links, and this website all give slightly different wordings for the quote.

Brian Gladish published The Society Most Conducive to Problem Solving: Karl Popper and Piecemeal Social Engineering in The Independent Review. I'm reposting my comments here.

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Thanks for sharing the article. I found your comments on Popper’s thinking much more accurate than most secondary sources.

In case you hadn’t seen it yet, I wanted to share Popper’s "The Power Of Television” (After the Open Society, ch. 48). In it, Popper advocates TV censorship, particularly regarding depicting violence. Excerpt:

What I propose is that such an organization be created by the state for all people who are involved in the production of television. Everybody who is connected with it must have a licence. This licence can be withdrawn from him for life, if he acts against certain principles. That is my way of introducing discipline into this subject. Everybody must be organized, and everybody must have a licence. Everybody who is doing something which he should not do by the rules of the organization can lose his licence – the licence can be withdrawn from him by a kind of court. So he is constantly under supervision, and he constantly has to fear that if he does something bad he may lose his licence. This constant supervision is something far more effective than is censorship.

Popper said this in 1992 and was particularly eager to have these ideas widely shared. It shows how limited his "lifetime drift toward classical liberalism” was.

Your article mentions Popper’s "complicated scheme of seminationalization”. I wanted to share with people what that means. The letter is available in After the Open Society, ch. 34. Quote:

The comparatively easy problem is the nationalization problem. I suggest, in brief, that the state should take a share of 51 per cent of the shares of all public companies (= with shares quoted on the Stock Exchange). However, (a) they should not be interfered with in general, only if the situation warrants it, and (b) only 40 per cent, or 41 per cent, of the income should go to the state to start with.

Although I admire and advocate Popper’s epistemology, this is awful.

I had a quick comment on this part of the paper:

But it is somewhat harsh to criticize Popper for this failure [to advocate anarcho-capitalism] because he had contemporaries who were better equipped to make this leap—Mises and Hayek, for example—but who did not.

Why bring up anarchism? That criticism would be harsh, but we can fairly criticize Popper’s rejection of minarchism, minimal and limited government, and classical liberalism.

Here’s the big picture as I see it. Popper gave us:

(1) Critical Rationalism & reason -> (2) linking arguments -> (3) freedom & non-violence -> (4) linking arguments -> (5) interventionist government

His 1-3 were correct and his 4-5 were incorrect. His 1 was especially original and valuable. We can form our own system using Popper’s 1-3 followed by Misean arguments linking freedom & non-violence to e.g. laissez faire capitalism and limited government. Or we could follow with anarchist arguments to replace 4-5. 1-3 function independently of what we think freedom & non-violence imply.

Popper’s 4-5 were unoriginal and added nothing significant to the debate. He basically followed Marx in thinking that true freedom requires the forcible prevention of economic exploitation, e.g. in OSE:

I believe that the injustice and inhumanity of the unrestrained 'capitalist system' described by Marx cannot be questioned

Note how blatantly he contradicts his own fallibilist epistemology which teaches us that all ideas can be questioned.

Anyway, Popper was right to link reason with non-violence (and right to link reason with evolution, to reject induction, etc.), and we can and should use that part of Popper’s thinking without using his Marxist followup.

What do you think?

PS: FYI, there’s a typo in the 12th endnote: “seemto” instead of “seem to”.

This is adapted from a Feb 2013 email. I explain why I don't think all justificationism is infallibilist. Although I'm discussing directly with Alan, this issue came up because I'm disagreeing with David Deutsch (DD). DD claims in The Beginning of Infinity that the problem with justificationism is infallibilism:

To this day, most courses in the philosophy of knowledge teach that knowledge is some form of justified, true belief, where ‘justified’ means designated as true (or at least ‘probable’) by reference to some authoritative source or touchstone of knowledge. Thus ‘how do we know . . . ?’ is transformed into ‘by what authority do we claim . . . ?’ The latter question is a chimera that may well have wasted more philosophers’ time and effort than any other idea. It converts the quest for truth into a quest for certainty (a feeling) or for endorsement (a social status). This misconception is called justificationism.

The opposing position – namely the recognition that there are no authoritative sources of knowledge, nor any reliable means of justifying ideas as being true or probable – is called fallibilism.

DD says fallibilism is the opposing position to justificationism and that justificationists are seeking a feeling of certainty. And when I criticized this, DD defended this view in discussion emails (rather than saying that's not what he meant or revising his view). DD thinks justificationism necessarily implies infallibilism. I disagree. I believe that some justificationism isn't infallibilist. (Note that DD has a very strong "all" type claim and I have a weak "not all" type claim. If only 99% of justificationism is infallibilist, then I'm right and DD is wrong. The debate isn't about what's common or typical.)

Alan Forrester wrote:

[Justification is] impossible. Knowledge can't be proven to be true since any argument that allegedly proves this has to start with premises and rules of inference that might be wrong. In addition, any alleged foundation for knowledge would be unexplained and arbitrary, so saying that an idea is a foundation is grossly irrational.

I replied:

But "justified" does not mean "proven true".

I agree that knowledge cannot be proven true, but how is that a complete argument that justification is impossible?

And Alan replied:

You're right, it's not a complete explanation.

Justified means shown to be true or probably true. I didn't cover the "probably true" part. The case in which something is claimed to be true is explicitly covered here. Showing that a statement X is probably true either means (1) showing that "statement X is probably true" is true, or it means that (2) X is conjectured to be probably true. (1) has exactly the same problem as the original theory.

In (2) X is admitted to be a conjecture and then the issue is that this conjecture is false, as argued by David in the chapter of BoI on choices. I don't label that as a justificationist position. It is mistaken but it is not exactly the same mistake as thinking that stuff can be proved true or probably true.

In parallel, Alan had also written:

If you kid yourself that your ideas can be guaranteed true or probably true, rather than admitting that any idea you hold could be wrong, then you are fooling yourself and will spend at least some of your time engaged in an empty ritual of "justification" rather than looking for better ideas.

I replied:

The basic theme here is a criticism of infallibilism. It criticizes guarantees and failure to admit one's ideas could be wrong.

I agree with this. But I do not agree that criticizing infallibilism is a good reply to someone advocating justificationism, not infallibilism. Because they are not the same thing. And he didn't say anything glaringly and specifically infallibilist (e.g. he never denied that any idea he has could turn out to be a mistake), but he did advocate justificationism, and the argument is about justification.

And Alan replied:

Justificationism is inherently infallibilist. If you can show that some idea is true or probably true, then when you do that you can't be mistaken about it being true or probably true, and so there's no point in looking for criticism of that idea.

My reply below responds to both of these issues.

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Justificationism is not necessarily infallibilist. Justification does not mean guaranteeing ideas are true or probably true. The meaning is closer to: supporting some ideas as better than others with positive arguments.

This thing -- increasing the status of ideas in a positive way -- is what Popper calls justificationism and criticizes in Realism and the Aim of Science.

I'll give a quote from my own email from Jan 2013, which begins with a Popper quote, and then I'll continue my explanation below:

Realism and the Aim of Science, by Karl Popper, page 19:

The central problem of the philosophy of knowledge, at least since the Reformation, has been this. How can we adjudicate or evaluate the far-reaching claims of competing theories and beliefs? I shall call this our first problem. This problem has led, historically, to a second problem: How can we justify our theories or beliefs? And this second problem is, in turn, bound up with a number of other questions: What does a justification consist of? and, more especially: Is it possible to justify our theories or beliefs rationally: that is to say, by giving reasons -- 'positive reasons' (as I shall call them), such as an appeal to observation; reasons, that is, for holding them to be true, or at least 'probable' (in the sense of the probability calculus)? Clearly there is an unstated, and apparently innocuous, assumption which sponsors the transition from the first to the second question: namely, that one adjudicates among competing claims by determining which of them can be justified by positive reasons, and which cannot.

Now Bartley suggests that my approach solves the first problem, yet in doing so changes its structure completely. For I reject the second problem as irrelevant, and the usual answers to it as incorrect. And I also reject as incorrect the assumption that leads from the first to the second problem. I assert (differing, Bartley contends, from all previous rationalists except perhaps those who were driven into scepticism) that we cannot give any positive justification or any positive reason for our theories and our beliefs. That is to say, we cannot give any positive reasons for holding our theories to be true. Moreover, I assert that the belief we can give such reasons, and should seek for them is itself neither a rational nor a true belief, but one that can be shown to be without merit.

(I was just about to write the word 'baseless' where I have written 'without merit'. This provides a good example of just how much our language is influenced by the unconscious assumptions that are attacked within my own approach. It is assumed, without criticism, that only a view that lacks merit must be baseless -- without basis, in the sense of being unfounded, or unjustified, or unsupported. Whereas, on my view, all views -- good and bad -- are in this important sense baseless, unfounded, unjustified, unsupported.)

In so far as my approach involves all this, my solution of the central problem of justification -- as it has always been understood -- is as unambiguously negative as that of any irrationalist or sceptic.

If you want to understand this well, I suggest reading the whole chapter in the book. Please don't think this quote tells all.

Some takeaways:

• Justificationism has to do with positive reasons.

• Positive reasons and justification are a mistake. Popper rejects them.

• The right approach to epistemology is negative, critical. With no compromises.

• Lots of language is justificationist. It's easy to make such mistakes. What's important is to look
  out for mistakes and try to correct them. ("Solid", as DD recently used, was a similar mistake.)

• Popper writes with too much fancy punctuation which makes it harder to read.

A key part of the issue is the problem situation:

How can we adjudicate or evaluate the far-reaching claims of competing theories and beliefs?

Justificationism is an answer to this problem. It answers: the theories and beliefs with more justification are better. Adjudicate in their favor.

This is not an inherently infallibilist answer. One could believe that his conception of which theories have how much justification is fallible, and still give this answer. One could believe that his adjudications are final, or one could believe that his adjudications could be overturned when new justifications are discovered. Infallibilism is not excluded nor required.

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Looking at the big picture, there is the critical approach to evaluating ideas and the justificationist or "positive" approach.

In the Popperian critical approach, we use criticism to reject ideas. Criticism is the method of sorting out good and bad ideas. (Note that because this is the only approach that actually works, everyone does it whenever they think successfully, whether they realize it or not. It isn't optional.) The ideas which survive criticism are the winners.

In the justificationist approach, rather than refuting ideas with negative criticism, we build them up with positive arguments. Ideas are supported with supporting evidence and arguments. The ones we're able to support the most are the winners. (Note: this doesn't work, no successful thinking works this way.)

These two rival approaches are very different and very important. It's important to differentiate between them and to have words for them. This is why Popper named the justificationist approach, which had gone without a name because everyone took it for granted and didn't realize it had any rival or alternative approaches.

Both approaches are compatible with both infallibilism and fallibilism. They are metaphorically orthogonal to the issue of fallibility. In other words, fallibilism and justificationism are separate issues.

Fallibilism is about whether or not our evaluations of ideas should be subjected to revision and re-checking, or whether anything can be established with finality so that we no longer have to consider arguments on the topic, whether they be critical or justifying arguments.

All four combinations are possible:

Infallible critical approach: you believe that once socialist criticisms convince you capitalism is false, no new arguments could ever overturn that.

Infallible justificationist approach: you believe that once socialist arguments establish the greatness of socialism, then no new arguments could ever overturn that.

Fallible critical approach: you believe that although you currently consider socialist criticisms of capitalism compelling, new arguments could change your mind.

Fallible justificationist approach: you believe that although you currently consider socialist justifying arguments compelling (at establishing the greatness and high status of the socialism, and therefore its superiority to less justified rivals), you are open to the possibility that there is a better system which could be argued for even more strongly and justified even more and better than socialism.

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BTW, there are some complicating factors.

Although there is an inherent asymmetry between positive and negative arguments (justifying and critical arguments), many arguments can be converted from one type to the other while retaining some of the knowledge.

For example, someone might argue that the single particle two slit experiment supports (justifies) the many-worlds interpretation of quantum physics. This can be converted into criticisms of rivals which are incompatible with the experiment. (You can convert the other way too, but the critical version is better.)

Another complicating factor is that justificationists typically do allow negative arguments. But they use them differently. They think negative arguments lower status. So you might have two strong positive arguments for an idea, but also one mild negative argument against it. This idea would then be evaluated as a little worse than a rival idea with two strong positive arguments but no negative arguments against it. But the idea with two strong positive arguments and one weak criticism would be evaluated above an idea with one weak positive argument and no criticism.

This is easier to express in numbers, but usually isn't. E.g. one argument might add 100 justification and another adds 50, and then a minor criticism subtracts 10 and a more serious criticism subtracts 50, for a final score of 90. Instead, people say things like "strong argument" and "weak argument" and it's ambiguous how many weak arguments add up to the same positive value as a strong argument.

In justification, arguments need strengths. Why? Because simply counting up how many arguments each idea has for it (and possibly subtracting the number of criticisms) is too open to abuse by using lots of unimportant arguments to get a high count. So arguments must be weighted by their importance.

If you try to avoid this entirely, then justificationism stops functioning as a solution to the problem of evaluating competing ideas. You would have many competing ideas, each with one or more argument on their side, and no way to adjudicate. To use justificationism, you have to have a way of deciding which ideas have more justificationism.

The critical approach, properly conceived, works differently than that. Arguments do not have strengths or weights, and nor do we count them up. How can that be? How can we adjudicate between competing ideas with out that? Because one criticism is decisive. What we seek are ideas we don't have any criticisms of. Those receive a good evaluation. Ideas we do have criticisms of receive a bad evaluation. (These evaluations are open to revision as we learn new things.) (Also there are only two possible evaluations in this system. The ideas we do have criticisms of, and the ideas we don't. If you don't do it that way, and you follow the logic of your approach consistently, you end up with all the problems of justificationism. Unless perhaps you have a new third approach.)

This wrote this on an Objectivist discussion forum in 2013.

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http://rebirthofreason.com/Forum/Dissent/0265.shtml

I wrote:

Observe what? There are always many many things you could observe. Real scientific observation is selective.

Perform which action? There are many many actions one could perform. Real scientific action is selective.

Which patterns? There's always many many patterns.

In each case, being selective requires complex (critical) thinking. Ideas come first. Induction is supposed to explain how thinking works, but actually presupposes it.

Merlin Jetton replied:

Okay. Give us your answer to these questions. Please give us simple methods that cover all possible cases. How do we delimit those infinitely many possible conjectures?

(Following Popper.) We don't run into all the same problems because we use different methods in the first place.

We don't start with observation, scientific experiment, or finding patterns. All of those come later, after you already have various ideas. Then you do them according to your ideas. This is not problematic in general. It is a problem when you say stuff is "step 1" that actually presupposes ideas, and then claim your set of steps is a solution in epistemology and is how we get ideas.

We have a different approach that is not like induction and avoids many of induction's problems. By using different methods some problems never come up. We never have the problem of figuring out what to observe before having ideas, for example, because we say ideas come first before observations.

How are ideas learned then? Not from observations. Ideas come first. That's not to say observations are excluded. Observations are very useful. But first you need some ideas. Then you can observe (selectively, according to your ideas about what is important, what is interesting, what is notable, what is relevant to problems of interest, what clashes with your expectations, etc, etc ... and if your way of observing doesn't work out you can improve it with criticism, you can change and adjust it) and use the observations to help with further ideas (in a critical role – they rule things out).

Now this is a hard issue and you haven't read the literature and don't be too ambitious about how much you expect to learn from a summary. But anyway, because it's hard I'm going to split it up. First we'll consider an adult who wants to learn something. Then we could talk about how a child gets started after. I'll save that for later if the adult explanation goes over OK. The child is the harder case. I think it's too much to do the child first, all at once.

So, one of Popper's insights is that starting places aren't so important. I'm guessing this sounds dumb to you, because you're a foundationalist and think you have to start with the right foundations/premises/basis and then build up from there, step by step, making sure not to introduce errors or contradictions as you go. And Popper criticized and rejected that approach and offered a significantly different approach.

So let me try to explain what Popper's approach is like. People make mistakes. People are fallible. Errors are common. People mess up all the time. This isn't skepticism. People also get things right, learn, acquire knowledge, make scientific progress, etc, etc... But it's important to understand how easy it is to make mistakes. Knowledge is possible but hard to come by. To get knowledge you have to put a ton of effort into dealing with the problem of mistakes. I think if you read this the right way, you could agree with it. Objectivism recognizes that lots of philosophies go wrong and using the right methods is important and makes a big difference and some stuff like that.

So, OK, error is common and a big part of epistemology and philosophy is how you deal with error. What are you going to do about it? One school of thought tries to avoid errors. You use the right methods and then you get the right answers. That sounds very plausible but I don't think it's the right approach. I'll try to talk about Popper's approach instead. Popper's approach is you do try to avoid errors but you're never going to avoid all of them in the first place. That's not the primary most important thing. Whatever you do, some errors are going to get through. What you really have to do is set up mechanisms to identify and correct errors.

Popper applied this approach widely. Take politics and political systems. One of Popper's big ideas about politics is that trying to elect the right ruler is the wrong thing to focus on. Electing the right guy is trying to avoid errors. Yes you should put some effort into that but you can't do it perfectly and it's not the most important issue. What is the most important issue? That errors can be identified and corrected. In politics that means if you elect the wrong guy you find out fast, and you can get rid of him fast and you can get rid of him without violence. Popper called the wrong approach the "Who should rule?" problem and said most political philosophy argues about who should rule, when it should be focussing a lot more on how to set up political systems capable of correcting mistakes about who gets to rule.

What about epistemology? "Which ideas should we start with?" is a bit like "Who should rule?" You're never going to get it perfect and it shouldn't be the primary focus of your attention. Instead you want to set things up so if you start with the wrong ideas you can find out about the mistake and fix it quickly, easily, cheaply.

error correction is (a lot) more important than starting in a good place. look at it another way. if you start in a bad place but keep making progress, after a while you'll get to a good place and keep going. but if you start in a good place but aren't correcting errors, there is no progress, things never get better, long term you're doomed. so error correction is the more crucial thing that you really need.

so how can adults be selective? how can they decide what scientific experiments to do or which actions and results to investigate? how can they decide what patterns to look for? answer: they already have ideas about that. they can use the ideas they already have. that's ok! they don't need me to tell them some perfect answer. i could give them some advice and there could be some value in it, but it doesn't matter so much. they should start with the ideas they already have, use those, and then if something goes wrong they can make adjustments to try to do something about it. (and they can also philosophically examine their ideas and try to criticize instead of waiting for something noticeable to go wrong.)

in one sense, we're both advocating the same thing. people can and do use the ideas they already have about how to be selective, what issues to focus on, which patterns are notable, and more. but we Popperians know that is what's going on, and know how to keep making progress from there even if people aren't great at it. inductivists on the other hand think they have this method from first principles that is how people think but actually it smuggles in all sorts of common sense and pre-existing ideas as unexamined, uncriticized premises. and that's a really bad idea. those premises being smuggled in are good enough to start with, but what you really need to do is examine and criticize them!

i have not addressed how children/infants get started. i also haven't explained how thinking works at a lower level. (being able to criticize and correct errors requires thinking. how is that done?). we can get to those next if what i'm saying so far goes over ok. also the very short answer for how thinking works is that evolution is the only known theory for how knowledge can be created from non-knowledge. human thinking, at a low level, uses an evolutionary process to create knowledge. (i mean thinking literally uses evolution, not metaphorically. and no i'm not saying you consciously do that).

I wrote this at an Objectivist forum in 2013.

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http://rebirthofreason.com/Forum/Dissent/0261.shtml

Popper is by no means perfect. The important thing is the best interpretations (that we can think of) of his best ideas. The comment below about "animals" is a good example. I do not agree with his attitude to animals in general, and I'm uncomfortable with this statement. However, everything he said about animals (not much) can be removed from his epistemology without damaging the important parts.

Popper made some bad statements about epistemology, and some worse ones about politics. I don't think this should get in the way of learning from him. That said, I agree with Popper's main points below.

1) Can you show if Popper ever fully realized that the falsification of a universal positive proposition is a necessary truth? In other words, if a black swan is found, then the proposition "All swans are white" is falsified, but more than that, it is absolutely falsified (which is a form of absolute knowledge/absolute certainty)? Even if you can't, please discuss.

No, Popper denied this. The claim that we have found a black swan is fallible, as is our understanding of its implications.

Fallibility is not a problem in general. We can act on, live with, and use fallible knowledge. However, it does start to contradict you a lot when you start saying things like "absolute certainty".

Rand isn't fully clear about this. Atlas Shrugged:

"Do not say that you're afraid to trust your mind because you know so little. Are you safer in surrendering to mystics and discarding the little that you know? Live and act within the limit of your knowledge and keep expanding it to the limit of your life. Redeem your mind from the hockshops of authority. Accept the fact that you are not omniscient, but playing a zombie will not give you omniscience—that your mind is fallible, but becoming mindless will not make you infallible—that an error made on your own is safer than ten truths accepted on faith, because the first leaves you the means to correct it, but the second destroys your capacity to distinguish truth from error. In place of your dream of an omniscient automaton, accept the fact that any knowledge man acquires is acquired by his own will and effort, and that that is his distinction in the universe, that is his nature, his morality, his glory.

"Discard that unlimited license to evil which consists of claiming that man is imperfect. By what standard do you damn him when you claim it? Accept the fact that in the realm of morality nothing less than perfection will do. But perfection is not to be gauged by mystic commandments to practice the impossible [...]

Here Rand accepts fallibility and only rejects misuses like claiming man is "imperfect" to license evil. Man's imperfection is not an excuse for any evil -- agreed.

Rand has just acknowledged that man and his ideas and achievements are fallible. But then she decides to demand moral "perfection". Which must mean some sort of contextual, achievable perfection -- not the sort of infallible, omniscient perfection Popper rejects and Rand acknowledges as impossible.

It's the same when Rand talks about "certainty" which is really "contextual certainty" which is open to criticism, arguments, improvement, changing our mind, etc... (Only in new contexts, but every time anyone thinks of anything, or any time passed, then the context has changed at least a little. So the new context requirement doesn't cause trouble.)

2) Can you offer something to redeem Popper of seemingly damning quotes such as:

In so far as a scientific statement speaks about reality, it must be falsifiable: and in so far as it is not falsifiable, it does not speak about reality.

... which preemptively denies the possibility of axiomatic concepts (i.e., the possibility of statements that speak about reality, but are not, themselves, falsifiable).

Any statement which speaks about reality is potentially falsifiable (open to the possibility of criticism using empirical evidence) because, if it speaks about reality, then it runs the risk of being contradicted by reality.

Popper does deny axiomatic concepts, meaning infallible statements. Statements that you couldn't even try to argue with, potentially criticize, question, or improve on. All ideas should be open to the possibility of critical questioning and progress.

There is a big difference between open to refutation and refuted. What's wrong with keeping things open to the potential that, if someone has a new idea, we could learn better in the future?

"If realism is true, if we are animals trying to adjust ourselves to our environment, then our knowledge can be only the trial-and-error affair which I have depicted. If realism is true, our belief in the reality of the world, and in physical laws, cannot be demonstrable, or shown to be certain or 'reasonable' by any valid reasoning. In other words, if realism is right, we cannot expect or hope to have more than conjectural knowledge."

... which preemptively denies the possibility of arriving at a necessary truth about the world.

Conjectural knowledge (or trial-and-error knowledge) is Popper's term for fallible knowledge. It's objective, effective, connected to reality, etc, but not infallible. We improve it by identifying and correcting errors, so our knowledge makes progress.

We cannot establish our ideas are infallibly correct, or even that they are good or reasonable. Such claims (that some idea is good) never have authority. Rather, we accept them as long as we don't find any errors with them.

I think this is different than Objectivism, but correct. Well, sort of different. The following passage in ITOE could be read as something kind of like a defense of this Popperian position (and I think that is the correct reading).

One of Rand's themes here, in my words, is that fallibility doesn't invalidate knowledge.

The extent of today’s confusion about the nature of man’s conceptual faculty, is eloquently demonstrated by the following : it is precisely the “open-end” character of concepts, the essence of their cognitive function, that modern philosophers cite in their attempts to demonstrate that concepts have no cognitive validity. “When can we claim that we know what a concept stands for?” they clamor—and offer, as an example of man’s predicament, the fact that one may believe all swans to be white, then discover the existence of a black swan and thus find one’s concept invalidated.

This view implies the unadmitted presupposition that concepts are not a cognitive device of man’s type of consciousness, but a repository of closed, out-of-context omniscience —and that concepts refer, not to the existents of the external world, but to the frozen, arrested state of knowledge inside any given consciousness at any given moment. On such a premise, every advance of knowledge is a setback, a demonstration of man’s ignorance. For example, the savages knew that man possesses a head, a torso, two legs and two arms; when the scientists of the Renaissance began to dissect corpses and discovered the nature of man’s internal organs, they invalidated the savages’ concept “man”; when modern scientists discovered that man possesses internal glands, they invalidated the Renaissance concept “man,” etc.

Like a spoiled, disillusioned child, who had expected predigested capsules of automatic knowledge, a logical positivist stamps his foot at reality and cries that context, integration, mental effort and first-hand inquiry are too much to expect of him, that he rejects so demanding a method of cognition, and that he will manufacture his own “constructs” from now on. (This amounts, in effect, to the declaration: “Since the intrinsic has failed us, the subjective is our only alternative.”) The joke is on his listeners: it is this exponent of a primordial mystic’s craving for an effortless, rigid, automatic omniscience that modern men take for an advocate of a free-flowing, dynamic, progressive science.

One of the things that stands out to me in discussions like this is that all today's Objectivists seem (to me) more at odds with Popper than Rand's own writing is.

I'll close with one more relevant ITOE quote:

Man is neither infallible nor omniscient; if he were, a discipline such as epistemology—the theory of knowledge—would not be necessary nor possible: his knowledge would be automatic, unquestionable and total. But such is not man’s nature. Man is a being of volitional consciousness: beyond the level of percepts—a level inadequate to the cognitive requirements of his survival—man has to acquire knowledge by his own effort, which he may exercise or not, and by a process of reason, which he may apply correctly or not. Nature gives him no automatic guarantee of his mental efficacy; he is capable of error, of evasion, of psychological distortion. He needs a method of cognition, which he himself has to discover: he must discover how to use his rational faculty, how to validate his conclusions, how to distinguish truth from falsehood, how to set the criteria of what he may accept as knowledge. Two questions are involved in his every conclusion, conviction, decision, choice or claim: What do I know?—and: How do I know it?