Finding Karl Popper on Facebook


Nobody would have ever heard of me if it weren’t for the Karl Popper Facebook page. It’s undoubtedly the most popular thing on the internet about Karl Popper at this moment. Since it wasn’t started by me, I will also write something about the founder, Jaakko J. Wallenius from Finland, and how I became the (co-)admin.

Several things caused me to become a reader. The most important one is the fact that I was often ill as a child (I couldn’t really do much else but read while ill). I also have never had the idea as a child or even as an adult of having the same kind of physical energy as most other people have. As the great football-player Johan Cruyff used to say: every disadvantage has an advantage. The advantage being that I have lived in the world of ideas from a very young age. I read lots of comic books as a kid. And later lots of novels. I also became interested in all kinds of subjects. 

My parents went bankrupt before I was twenty, so I didn’t really have enough money to buy books myself until I was about 25, when money became somewhat less of a problem. I went to the library before that (I still do). I live in Oudenaarde, which is quite close to the city of Ghent, where they have a university. They used to have a great bookshop there, with books about all kinds of subjects in many languages. So when I was about 25, I went there and bought books regularly. 

I first bought Magee’s booklet1. Since that looked interesting, I started reading The Open Society and Its Enemies. At the time I was following evening-classes in order to become a tax consultant. So I didn’t really have a lot of time. I read The Open Society during my noon-break. That wasn’t ideal; it took me a long time, but it did make an impression on me. It has been my favorite book ever since. 

What was so special for me about The Open Society? First of all, I was impressed with the quality of the prose. In some places, it’s like poetry. And it’s full of arguments. The book is not about one thing. It’s about many things. My favorite parts are chapter 10, 24 and the addenda. Anybody who thinks The Open Society is not worth the time it takes to read it, should have a quick look at these parts. The same is valid for the first chapters of Conjectures & Refutations. Tanny Clapsaddle blogged about his experience reading Conjectures & Refutations for the first time2. I surely cannot do it any better.

It was the first time that I had the idea that I was reading a book that was written by a genius. No other book ever had more influence on me. What is an open society? Well, if you want to know, read the book! If I have to give a short version, I would say that it is a society with open borders for criticism3 (we can all be wrong, so we should listen to each other), where all power is limited (including the power of the majority), and where the weak are protected (including those who are weak because they belong to a minority). It’s a society that allows us to learn from our mistakes. In Popper’s words, it is a society in which “we can say that, in our search for truth, we have replaced scientific certainty by scientific progress”4. It’s about the emancipation of the individual. It’s about freedom and responsibility for the individual human being. Insofar as Popper wants to protect the weak, his views have something in common with Amartya Sen’s Development as Freedom

Open Society is also against some things. Tribalism and racism. Nationalism. A single ideology proposed by the State. That you need to meet specific criteria and behave in a certain way in order to belong to the Volksgemeinschaft. Open Society is against the idea of a Volksgemeinschaft. Against the idea that some people have more rights than others. It is also about the burden of freedom. Against the idea of Utopian change and that everything will be ideal in a prespecified future perfect society.

Open Society is not perfect, but is open to change, and thus to change for the better. But everything we have achieved can be lost. The future is our responsibility.

The optimism of Karl Popper is not a blind faith in progress. It is an ethical decision, our duty to do whatever we can to make the world a better place. We need to be optimistic in order to do this. But we should never have the blind faith that our knowledge will be able to solve this or that problem. 

Something important is that the kind of individualism that Popper promoted is not egoism. As he explained, an individual can be altruistic, and tribal selfishness is quite common5

Popper is famous for some of his paradoxes: the paradox of freedom, the paradox of tolerance and.. the idea that disagreement causes the growth of knowledge. Whenever I give that last quote, people tend to comment with ‘I disagree!’. 

Yes, Popper was all in favor of diversity.

I kept on reading books by Popper and lots of other books too. By reading more of Popper, I also became interested in epistemology and the philosophy of science. As Peter Medawar wrote, Popper’s views on politics and on science have something in common: “What they have in common is the element that pervades the whole of Popper’s philosophy: the recognition that human designs and human schemes of thought are very often (perhaps more often than not) mistaken, and that the safest way to proceed is to identify and learn from our mistakes and learn always to do better next time. By this means, Popper believes, as I also believe, the world can be made a better place to live in.”6  

As Mariano Artigas showed convincingly in one of my favorite books7, Popper’s views on politics are not derived from his views on science. It’s actually the other way around8. The whole philosophy of Karl Popper is based on an ethical decision: “Fallibilism appeared, above all, as an ethical duty.”9

 I kept on revisiting Popper’s ideas and reading his work. At some point, I gave a speech about Popper in the town hall of Oudenaarde10 (looking back on this, I don’t think my speech was any good). But then, about fifteen years later, something fortunate happened. I was out of a job, and had some spare time to check out what that Facebook thing was all about. I discovered that there was a Facebook page about Karl Popper, started by Jaakko Wallenius from Finland. Jaakko had cancer, so he had the time to do this. He also started several other pages. The most successful is the Russell-page. It is still very popular today. At the time, I sent Jaakko some tips and quotes to use on the Karl Popper Facebook page. And after a few months he asked me to become co-admin. 

Jaakko couldn’t be operated on, but they were able to fight the cancer with medicines. But then, a few months after he asked me to become co-admin, the drugs stopped working, and the treatment was stopped. He died soon after. Since then, the Karl Popper page has no admin.

Jaakko was addicted to reading. He taught himself to read by being very curious about what his elder brother was learning in school. I have never met anybody who had read more books than Jaakko.

The Karl Popper Facebook page is now the most successful thing about Karl Popper on the internet. That was only possible thanks to all the people who have helped me. There are so many that I can’t list them all, and I’m afraid that I would forget somebody11

Taking care of the page has been a lot more work than I ever expected. And it has also been much more pleasant than I ever expected 12 . I have ‘met’ a lot of people online that I now see as friends, though I have never met them personally. Thanks to Margaretha Hendrickx, who organized the 24-hour-zoom-meet-and-greet, I was also able to meet some of them on Zoom. I hope to meet you too next time!

[1] I love everything that I have ever read of Bryan Magee. Certainly don’t forget his three-volume biography that starts with Clouds of Glory, a Hoxton childhood. The title of the booklet I refer to is Popper. There is also a US-edition with a different title.
[3] I took that way of saying it from Herbert Keuth, who used it in a podcast.
[4] The Open Society and Its Enemies, Princeton University Press edition,1994, p. 229
[5] “Plato suggests, and all later collectivists followed him in this point, that if you cannot sacrifice your self-interest for the sake of the whole, then you are a selfish person, and morally depraved. But this is not so, as glance at our little table may show. Collectivism is not opposed to egoism, nor is it identical with altruism or unselfishness. A collectivist can be a group-egoist. He can selfishly defend the interest of his own group, in contradistinction to all other groups. Collective egoism or group egoism (e.g. national egoism or class egoism) is a very common thing. That such a thing exists shows clearly enough that collectivism as such is not opposed to selfishness. On the other hand, the individualist or anti-collectivist can at the same time be an altruist. He can be ready to make sacrifices in order to help other individuals. (….) To be an individualist means to see in every human individual an end in itself, and not merely a means to further other interests, for example, those of the state. It does not mean to take one’s own individuality particularly seriously, or to lay more stress (or even as much) on one’s own interests than on the interests of others.” Karl Popper, ‘After The Open Society’, Chapter 7.
[6] Peter Medawar, ‘The Philosophy of Karl Popper’ (can be found in “The Threat and the Glory”).
[7] Mariano Artigas, ‘The Ethical Nature of Karl Popper’s Theory of Knowledge’. Part of the book can be found online:
[8] Originally. I guess you could say that the influence went both ways after that.
[9] From the book of Mariano Artigas.
[10] I gave the speech in the Schepenzaal, the most beautiful room of the town hall of Oudenaarde. With paintings of Adriaen Brouwer on the wall! The portal you see here is from the inside of the room (it’s the entrance):
[11] I do have to thank Bruce Caithness for having taken a look at this text before it was published.
[12]  One of the things that I will never forget is when Phil Wood found a letter in his second-hand Schilpp-volumes:

luc castelein1 Luc Castelein

Oudenaarde, Belgium – Contributor

Luc is a retired accountant and Linux afficionado.   He discovered the philosophy of Karl Popper in the mid-1980s and is the current administrator of the Karl Popper Facebook page to which he contributes weekly. He was one of the co-hosts of the 24 hr. Transcontinental Popperian ZOOM Meet ‘n Greet of January 9-10, 2021.  He can be contacted at luc.castelein[at]telenet[dot]be.


  1. You do a wonderful job, Luc. Your posts are a constant reminder of the value of Popper’s work and a prompt to do the most important thing, which is to go back and re-read him.


  2. Thank you, Luc.. I learnt a lot from your posts.. That is for sure the good side behind using the social media!


  3. I read somewhere long ago that Karl Popper considered himself a formal agnostic. Is this true do you know Luc?

    I have some not all of Popper’s Books. The first I read was The Open Society two vols and the second Unended Quest. I have since read part of Objective Knowledge, The Poverty Of Historicism, part of Realism And The Aim Of Science, and dipped into others.

    Andrew Oliver


  4. He was an agnostic. I don’t know what you mean with ‘formal’. I think you should read Conjectures & Refutations.


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