The best books on The Vienna Circle

Before we get to the books, let’s start with the obvious question: what was the Vienna Circle?

The Vienna Circle was a group of philosophers, all of whom had mathematical and scientific training, who began to meet in 1924; their discussion group continued for a dozen or so years. They were, effectively, disbanded when the fascists took over in Austria in 1934 – and then, in 1936, their urbane leader, Moritz Schlick, was murdered. They had a radical new approach to philosophy. They attacked metaphysics and many of the questions that have traditionally been discussed by philosophers. They claimed that many of these questions lack meaning.

And is it fair to say that they were on a drive to put philosophy on a scientific footing; that their approach was very much linked with mathematics and science? It’s not the literary end of philosophy that we’re talking about here.

They’re very much part of the scientific tradition of philosophy and, in a way, they saw philosophy as a branch of science. They wanted to make sense of the new science – the science of Einstein and Heisenberg, of relativity and uncertainty – they were interested in the question of what science should be doing, the language, claims and status of science. They thought that, for anything to be meaningful, it had to be either subject to some kind of verification test, or analytic, that is to say true or false by virtue of the meaning of the terms involved in the proposition. So, a claim like ‘water boils at a hundred degrees centigrade’ is a claim that they would allow as meaningful because it can be tested. A claim such as ‘all bachelors are unmarried’ is also acceptable to them because that is analytically true (i.e. true by definition).

What they rejected was a whole swathe of statements, to do with morality, with aesthetics, with theology, which fall into neither of those two categories. In other words, statements that were neither analytically true, nor verifiable—they can’t be tested.

So, that’s the philosophical content, but the social context is very interesting, as well. Your book, The Murder of Professor Schlick, is a combination of philosophy, biography and discussion of the historical milieu. Could you say something about Vienna in the 1930s and why it was such an important place intellectually?

The Circle begins in the 1920s. Moritz Schlick arrives in Vienna in 1922 and the Circle, the discussion group, begins to meet in 1924. There’d been a precursor to it 15 years or so earlier, with a few of the Circle’s members, who used to have discussions in coffee bars. Vienna at the turn of the 20th century was the most amazing place. Lots of people have written about it. It can be compared to Athens in 400 BC, or Florence during the Renaissance. For various reasons an extraordinary set of talented people emerged in lots of different disciplines. There were artists, brilliant writers and poets, journalists and musicians. Of course, too, it was the home of psychoanalysis, with Sigmund Freud; it was the home of Theodor Herzl and the birthplace of Zionism. There were important political thinkers, many of them Marxists. There were very important economists too. So an extraordinary range of talent. And the Vienna Circle was an important part of that.

“In a way, they saw philosophy as a branch of science”

My thesis is that it’s not a coincidence that there was darkness just around the corner. Of course, the fascists didn’t come to power until 1934, but they were already on the horizon in the 1920s. It was very difficult to be politically neutral in Vienna. There was a sense that they were on the edge of an abyss and this added to the cultural ferment and the sense of academic urgency.

Vienna was a cosmopolitan melting pot. The Austro-Hungarian Empire broke up in 1918, at the end of the First World War. But, in Vienna, you have Hungarians, Czechs, people from Galicia in the far east – you have people from all parts of the Austro-Hungarian Empire. I think that melting-pot aspect helped, too. It was politically very fraught, because there were Marxists and fascists and everybody in between.

A lot of the political discussions went on in coffee houses. Is that how the Vienna Circle operated? Or was it largely university-based?

They had an official meeting place which was university-based, but they would carry on their discussions in coffee houses. They had their favourite coffee houses. There was a tradition of der Stammtisch, the regulars’ table. Different members of the Circle had their favourite regulars’ table in different coffee houses, including the Josephinum and the Herrenhof.

So they had formal discussions and then informal discussions, and the advantage of the informal discussions was that you could then be joined, not just by the philosophers of science in the Circle, but others too. But when people talk about the Vienna Circle, they’re usually referring to the more formal meetings that would take place on a Thursday evening in the mathematics institute in Boltzmanngasse, part of the University of Vienna.

One more question before we get on to your choice of Five Books: what percentage of the Vienna Circle were Jewish?

About half. And of the ones who weren’t, most people thought they were! So Moritz Schlick, the leader of the Vienna Circle, was not Jewish. He was a very successful chair of the Vienna Circle because he was a mild-mannered, modest man. He was not particularly charismatic, but he was diplomatic and was able to manage the big egos in the Circle, people like Otto Neurath who, to use a cliché, was a larger-than-life character. Rudolf Carnap, another crucial figure in the Vienna Circle, wasn’t Jewish. And Kurt Gödel, whom Bertrand Russell mistakenly described as Jewish, was not Jewish. But most of the rest of the members were half or fully Jewish. Most of them came from similar Jewish bourgeois families, second or third generation children of parents or grandparents who had come from the eastern parts of the Austro-Hungarian Empire, like Galicia or Moravia or Bohemia.

They all had university degrees, obviously, and PhDs. That wouldn’t necessarily have been true of their parents, and almost certainly not true of their grandparents. But they had now entered the middle classes. They were almost, without exception, secular – they’d abandoned any religious trappings. But, beyond that, some of them had officially shed their ethnic labels too and converted—in Karl Popper’s case it was his parents who converted to Protestantism. There were lots of reasons why they might do that, chief among them the rampant anti-Semitism in Vienna. What’s fascinating is that although they were assimilated and, in many cases, no longer even officially Jewish, they nonetheless mingled, almost exclusively, with other Jews of a similar background. They remained within a Jewish world, but a very different world from that of the religious Jews who lived in a different part of Vienna.

Obviously, none of that would have saved them from Hitler and the Nazis, because you only had to have one grandparent who was Jewish to count as Jewish?

Strictly speaking, you had to have at least three to be treated as fully Jewish. That’s relevant to Ludwig Wittgenstein’s family. He and his siblings successfully ‘redefined’ one of his grandparents. So, he ceased being three-quarters Jewish, which is what he was, and became one-quarter Jewish, as did his siblings. That is how his two sisters were able to survive the war while remaining in Vienna; their ‘Mischling’ (mixed race) status saved them. But, for the rest of them, you’re absolutely right. Someone like Popper didn’t regard himself as Jewish because his parents had converted, but that wasn’t going to save him. He was 100 per cent ethnically Jewish from Hitler’s point of view. The fact that his parents had become Lutheran was irrelevant to the Nazis. And, in fact, despite not being officially Jewish, Karl Popper was beset by anti-Semitism throughout the Austrian part of his life. That was the reason he planned to leave Vienna, well before the Nazis arrived following the Anschluss. He couldn’t make any career progress, in part because of the strict quotas on Jews getting on in the university. So, he was regarded as Jewish, even though he himself didn’t self-define as Jewish.

Let’s go to your first book choice, Language, Truth and Logic by A. J. Ayer—quite a bombshell of a book in English philosophical circles. Why did you choose this book?

Well for autobiographical reasons, really; without Ayer my book would not have been written. More than that, without Ayer, I may not have gone into philosophy in the first place. He captured me—or enticed me—into the world of philosophy, as he did many people. I read Language, Truth and Logic when I was 19. I was a militant atheist, as Ayer probably was. I thought that belief in God was not only stupid, but harmful as well. And Ayer provided me with the ammunition, as a teenager, to be entirely dismissive of religion and—I feel embarrassed about this now—entirely dismissive of religious believers too.

At the heart of this book is the Verification Principle, which you’ve described very succinctly already, this idea that, for anything to be meaningful it must be either verifiable or falsifiable empirically or else true by definition—as philosophers say, ‘analytic’. Interestingly, in relation to God, it’s not clear Ayer was an atheist in the conventional sense, because he thought the statement ‘God exists’ to be literally meaningless. It could be neither true nor false. Atheists typically believe that ‘God exists’ is meaningful, but false. Ayer thought it was just meaningless verbiage.

In a way, it’s going even further, it’s even more of a fundamental objection to religious belief. He’s saying that religious believers can’t even discuss the nature of religion in the way they purport to, because, although they are uttering words, those are just a series of sounds that don’t connect to reality in any way. It’s a very radical critique of aspects of religious belief.

Of course, there are cultural aspects of religious belief that are entirely okay to discuss. So, it’s perfectly okay to say that X per cent of people are Christian or Muslim and that these people believe in X, Y and Z and that they engage in the following rituals…. The sociology of religion and the history of religion are unthreatened by logical empiricism, but statements such as ‘God believes that we should all behave in this way or in that way’—those are the sorts of propositions that Language, Truth and Logic attacks.

Like most of the Vienna Circle, or maybe all of the Vienna Circle, Ayer used the term ‘metaphysics’ as an insult. Metaphysics used to be thought of as at the core of philosophy and probably, in some corners of the subject, still is. For the Vienna Circle, metaphysics was something to be shunned and ridiculed. It wasn’t just a question of ‘don’t talk about God’. It was that any untestable statement or proposition about reality is metaphysics and not worth our time.

Correct. That includes ethics, aesthetics and the parts of religion we’ve been talking about here. The first line of the book is: “The traditional disputes of philosophers are, for the most part, as unwarranted as they are unfruitful.” And then, on the first page, he goes on to attack “metaphysical utterances”.

The logical empiricists have various enemies. But, really, a principal enemy is Heidegger. They thought that, essentially, Heidegger thought and spoke meaningless gibberish; that he purported to be deep and profound, but that many of his famous statements about ‘nothingness’ and so on, didn’t connect to the world in any way. They were literally meaningless. They might have had some kind of emotional impact on us, but they had no cognitive meaning. They thought that if you wanted to say something of emotional depth, philosophy wasn’t the appropriate vehicle. If you wanted to have a deep impact on people about the beauty and awe-inspiring nature of the universe, you should really be writing poetry or novels, not philosophy. That was Ayer’s view and the view of the logical empiricists.

“When people talk about the Vienna Circle, they’re usually referring to the…meetings that would take place on a Thursday evening in the mathematics institute in Boltzmanngasse”

The appeal of Language, Truth and Logic is that it’s a very short book—it’s only about a hundred and fifty pages long—and he doesn’t brook any doubt. It’s a book packed full of certainty. It’s polemical and it was very important in the history of logical empiricism because it brought the ideas of the logical empiricists from Vienna into the Anglo-American world. Almost all the Vienna Circle ended up in the Anglo-American world and had an impact on its philosophy, but it was this book, in particular, that translated the ideas of the Vienna Circle to the Anglo-American world and made them popular. Bizarrely, the second edition, which came out just after World War II, became a bestseller.

It was first published in 1936, I think. Ayer was very young and it was based on his one visit to Vienna, where he took part in the discussions of the Vienna Circle. It wasn’t written at a distance.

Yes. He spent several months there after taking his undergraduate degree. His German was rudimentary, so he was relatively quiet during meetings; unusually quiet, because he was normally quite garrulous. He happened to be there at the same time as Willard van Orman Quine, who was another visitor, from the United States. Quine was a much better linguist: he participated more fully in Circle meetings. But the two of them got to know each other quite well in Vienna.

You wouldn’t necessarily pick this up from Ayer’s book, but within the Vienna Circle there was very strong disagreement. They disagreed about many aspects of the Verification Principle and how it could be applied in various domains. Ayer’s view is, in some sense, a simplistic version of the Circle’s position – and certainly not one that everybody in the Circle would have signed up to. But, if you read it when you’re nineteen, as I was, it’s very exciting. And historically it was important in its influence on British philosophy.

I’ve got one more question before we move on. It seems to me that it’s an iconoclastic book. Do you think that the Vienna Circle was iconoclastic? Was Ayer typical in that sense? You were saying that they were subtler in some of their discussions, but they do seem to want to smash stuff up.

Yes. They do vary in personality. There isn’t one homogeneous personality. I don’t think the leader of the Vienna Circle, Moritz Schlick, was a ‘smasher’. I don’t think he wanted to take a big mallet and hit other philosophers over the head with it. But there were certainly members of the Circle—and Otto Neurath is a classic example—who were mallet grabbers and smashers and who really did want to make a noise and cause damage. It’s true that their philosophy was very radical, but some of them wanted to whisper about it, and others wanted to shout about it. Schlick was a whisperer; Neurath was a shouter.

That’s really interesting because sometimes there’s a delight in iconoclasm itself. And sometimes it’s a question of just wanting to get something right, of wanting to be right about how things are and dismissing things that are obstacles to that.

Yes. Their philosophy was iconoclastic, but they didn’t all share a view about the tone in which their philosophy should be broadcast to the world. Their famous manifesto, which was written in 1929 to thank Moritz Schlick for staying in Vienna when he could have taken a job elsewhere, summarizes their vision and ideas, but was not written by Schlick. Schlick was slightly embarrassed about the tone of it; it was more strident than he was comfortable with. It was strident because one of the lead authors was Neurath, and, as I’ve said, that was his character. But, you’re right, the philosophy itself was iconoclastic.

Let’s move on to your second choice, The World of Yesterday by Stefan Zweig. I’m ashamed to say I haven’t read the book, though I own it.  

You really, really should read it, not because of the Vienna Circle, but just as a work of literature. It is a beautiful book. As a chess player, I first came across Zweig’s novella The Royal Game, which is a wonderful short story about chess.

I have read that one.

It’s a great book, but The World of Yesterday is regarded by many Zweigians as his masterpiece. It’s an autobiography, but it’s also a biography of Vienna, really. And it’s incredibly poignant, because the day after he dispatched the manuscript in 1942—by which time he had left Vienna for the UK and then gone to the States, before reaching his final destination in Brazil—he and his wife killed themselves.

So, this biography covers the period of the build-up and flourishing of the Vienna Circle quite precisely.

Yes, it does. Some of it predates the Vienna Circle. It’s about the world of Klimt and Schiele, for example, the world of Mahler and the playwright Arthur Schnitzler.

That’s the cultural background leading up to this.

It certainly is. Klimt and Schiele are a bit before the Circle. Schiele died incredibly young – he was only 28 – in 1918, so before the Circle got going. The book portrays Vienna in its golden era and the passing stars in it are people like Klimt and Schiele, Mahler, and of course Freud.

The book is also important for me in relation to the discussion we had earlier about the backgrounds of the Vienna Circle members. Zweig was from a similar background. He was middle-class and Jewish but wasn’t observant. In one sense, he was established and successful and he saw himself as part of German high culture. Beethoven was one of his gods, as he was for so many Viennese. Wittgenstein described Beethoven as his god.

“Vienna at the turn of the 20th century was the most amazing place…It can be compared to Athens in 400 BC, or Florence during the Renaissance”

Zweig was bourgeois, successful and established – and, yet, vulnerable. The book is suffused with a sense of foreboding about what’s around the corner. Of course, he was writing about his past from the vantage point of knowing what was to happen – not surprisingly, the book is nostalgic for the earlier, fin-de siècle Vienna, and the Vienna of the 1910s and 20s.

I should add that he doesn’t just paint a golden picture of Vienna. He describes Vienna during the Great Depression and how miserable it was for a very large chunk of the Viennese population. While explaining how bad things got after the hyperinflation of the 1920s, he notes that a shoelace came to cost as much as an entire luxury shop with a stock of 2,000 pairs of shoes. And repairing a broken window became more expensive than building the whole house had once been. It’s very vivid. It’s a wonderful depiction of just how crazy hyperinflation had become in the mid-1920s.

Do you think that, in order to understand the Vienna Circle’s philosophy, this cultural background is essential, or desirable, or just interesting?

I think it’s absolutely essential. And that’s what I didn’t understand before I began to write the book. I came to believe that the attack on metaphysics is not just philosophical, but political. I’ve always believed that Heidegger’s anti-Semitism, unlike Frege’s anti-Semitism, was deeply embedded in his philosophy, which makes him, in some ways, a much more reprehensible figure—and certainly a much more pernicious philosopher, in my view. And there’s definitely a connection between some of the pseudo-metaphysics and Romanticism of the far right and logical empiricism’s attack on metaphysics.

Why were they so anti metaphysics?

Well, obviously, they had their philosophical objections. But what was driving that emotionally was a fear of fascism. And for very good reasons. The far right had all these metaphysical propositions at the heart of its philosophy: the connection with the ‘Heimat’ – the homeland; the idea of a group, the Volk, that was somehow more than the sum of the individuals; the idea of a spirit, and a movement of history. All these notions and sentiments, which were part of that metaphysical tradition, were deeply threatening on a personal level to members of the Vienna Circle.

At the same time, I suspect many of them were Marxists. And Marx had behind him Hegel, who was a big metaphysician and, presumably, also a target of the Vienna Circle.

You’re right. Hegel was a target. It would be going too far to say they were Marxists, with one or two exceptions, including, again, Otto Neurath. He’d spent some of his career working on command economies. In World War I, he had spent time looking at how you could set up a command economy and why that might be more successful, he argued, than one based on free markets. That’s a proposition that we now regard as absurd, I think. Most of the rest of the Circle, with the notable exception of Schlick, were people of the left, rather than Marxists. You might call them socialists, but not Marxists.

So, they could be critical of the Hegelianism behind Marx, but commit to socialism—not National Socialism—but the socialist left?

Yes, with the exception of Neurath who, I think, might have signed up to the movement-of-history aspect of Marx…

…but as an empirical hypothesis, rather than some inevitable determinism?

Yes. Marx has a sort of analytic approach to why society is bound to progress and eventually end up in the proletarian revolution. That is an empirical claim, as Popper famously pointed out. If Marxism is a science, which Marx himself claimed it to be, then, Popper said, it had to make these verifiable or, as he would put it, falsifiable claims. And, as Popper pointed out, Marx made many claims that turned out to be false.

So, it wasn’t meaningless, in other words.

It was science in Popperian terms. It was just bad science.

Is it bad science to make hypotheses which are refuted? I don’t think so. It could be good science. It’s just a bad hypothesis. It wasn’t bad science because it was setting yourself up to be refuted.

That’s right. Popper’s point was that Marx had come up with this hypothesis, this theory. It might be based on sound reasoning. Maybe you look at his premises and you think that they make sense. You can see how he reached his conclusions. But then you look at the predictions, and many of them turn out to be false.

So, in that sense, you’re right. It may have been a perfectly reasonable theory, which has nonetheless been falsified and so needs to be rejected. Or you can take the approach that Popper was even more critical of: namely, you reinterpret Marxism in a way that is never falsifiable.

Yes, so you can generate a whole series of these ad hoc clauses, which keep escaping the criticisms.

You explain every exception away, so that nothing is falsifiable. And if you do that, Popper says, you’re not engaging in a genuine scientific enterprise.

Let’s move on to your third choice, which is The Vienna Circle by Friedrich Stadler. What kind of a book is this one?

It’s a very odd book in many ways. It’s 983 pages long. It contains bits of documents, short biographies of all the members of the Vienna Circle, minutes of some of the meetings. For anybody interested in source material for the Vienna Circle, it’s absolutely indispensable. It was very important for me because it contains some of the documents linked to the murder of Moritz Schlick; he was killed by a deranged student. There are various court documents associated with that murder in the book. There are also some articles that appeared after Schlick’s shooting, in which one person in particular—basically a Nazi philosopher—came out in support of the murder, saying it was justified. This book is not bedside reading. But if you’re interested in the Vienna Circle, this is the book to go to for source material.

And has it got a narrative or is it just an anthology?

It doesn’t really have a narrative, no. It lurches from one part of the Circle to another. A whole section is just lists of biographies. It came out in 2001 and it’s the culminating work of the author, a lovely man called Friedrich Stadler. He founded and was the long-term director—I think he’s just now retired—of the Vienna Circle Institute, which is based in Vienna and is devoted to keeping the ideas of the Vienna Circle alive and to studying the history of the Vienna Circle.

I would say it’s a very generous book because it’s a book that passes on to the future historian or biographer a great wealth of material and puts it all in one place. So it’s not a book you would go to for narrative, but it’s a book you would go to for facts!

Brilliant. Let’s move on to number four, Frank Ramsey: A Sheer Excess of Powers by Cheryl Misak. This is the biography of Frank Ramsey, whom Hugh Mellor described as the greatest ever Cambridge philosopher, but who died tragically young.

He’d just turned 27. He was born in 1903.

He was quite clearly a genius in many respects, not just in philosophy, but specifically in mathematics. He was a mathematician by training but made significant contributions to philosophy and economics and game theory. His interest in some of these areas was almost a hobby, it seems. But his ideas were highly original.

Yes. The word ‘genius’ is bandied around, but with Ramsey, it is clearly totally appropriate.

He’s obviously much neglected in the wider world as a thinker, but he was a Cambridge-based philosopher. How does he connect with the Vienna Circle?

He was Cambridge-based. He did his undergraduate degree at Cambridge. And, already as an undergraduate, he was recognized as a great mind. He has several connections with the Vienna Circle. Most importantly, he went off to Austria when he was still an undergraduate to visit Wittgenstein, who at that stage had become a primary school teacher in small villages in southern Austria. He went to talk to him about his German manuscript, the Tractatus Logico-Philosophicus, which Ramsey then translated. So, he’s a very important figure in Wittgenstein scholarship. He was his first translator, which is remarkable, given how young he was at the time.  Wittgenstein himself, of course, was an important inspiration for the Vienna Circle.

We’re talking specifically here about the early Wittgenstein of the Tractatus—not just as a matter of dates, but because the Tractatus was thought of as a major work by the Vienna Circle because of what seemed to be its conclusions.

Yes. Now, Cheryl Misak makes two very important claims in connection with Ramsey and the Vienna Circle. She claims that it was Ramsey’s discussion with Moritz Schlick that brought the Tractatus to the attention of the Circle.

So, they didn’t know about Wittgenstein before that?

No. At least – according to Cheryl – they didn’t know about the Tractatus. She notes a reference to Schlick talking about the Tractatus, in which he mentions his discussions with Ramsey. It may be that that was the first time Schlick became aware of the Tractatus. And then he brought it to the attention of the Circle – and then they went through it literally line-by-line.

The second huge claim she makes about Ramsey and the Circle is that it was Ramsey who gave the Circle the idea that mathematics should be treated as consisting of analytic propositions. There had always been a puzzle about how to treat mathematics. Was it empirical? Was 2+2=4 out there in the world, to be observed, as some philosophers of mathematics have believed? That was John Stuart Mill’s approach to mathematics. According to Cheryl Misak, it was Ramsey who put into the minds of the Vienna Circle the idea that perhaps mathematical proofs should be treated like logical tautologies—propositions like ‘all bachelors are unmarried men’—that mathematical proofs are true by definition.

In some ways, it’s remarkable that no full biography had ever been written about Ramsey before Misak’s, given that he was so obviously a genius. I think the reason for that is that not many people have sufficient depth of knowledge across all the different areas of his expertise. You have to be a polymath. You have to be able to tackle his economics, his maths, his probability and his game theory, his decision theory and his philosophy. That’s a tough proposition. He also died young, which is a problem for biographers, obviously. There’s a limit to how much material you’ve got. And then, perhaps the biggest obstacle of all, was that he was relatively normal. He wasn’t a kind of crazy genius.

And yet Cheryl Misak’s written this beautiful book. It’s a huge book, 500 pages, and I don’t think anybody will ever attempt—this is my scientific, falsifiable prediction!—another biography of Ramsey again.

One of the ways she got around one of those difficulties was by getting experts to write summaries of some of the key papers that he wrote.

Yes, a clever technique. She did get experts to write these boxes, which are often very technical. She doesn’t exactly encourage the reader to bypass them, but she says it’s forgivable if they do!

As well as the connections we’ve been talking about between Ramsey and the Circle, she’s very interesting on Ramsey in Vienna. As I mentioned, Ramsey first went to Austria specifically to talk to Wittgenstein. But then he went back – this time to Vienna – to be psychoanalyzed. He’d had a disastrous love affair and going to Vienna was THE place, of course, to be psychoanalyzed. You didn’t go to your local psychoanalyst in London.

That’s the period before Vienna came to North London.

Yes, although Ramsey is one of the people who helped spread the word about psychoanalysis back in the UK and, specifically, in Cambridge. The elite Cambridge intellectual society, The Apostles, discussed the status and nature of psychoanalysis.

I agree that it’s a fascinating book and Ramsey is fascinating beyond his philosophy, too. He was an interesting character. As you say, he was quite grounded and a very generous man. An interesting, complex character. Very different in character from the intense and intolerant Wittgenstein. So, that’s a book you’d recommend for all kinds of reasons. In itself it’s a great biography, but it also gives insights into some aspects of the Vienna Circle, both its intellectual and cultural milieu.

Yes. For the purposes of this Five Books interview I wanted to choose one book that was specifically focused on a character who was either in the Circle or linked to the Circle. Ramsey was one of those characters. I could have chosen a whole array of very good books about some of the other characters in the Circle. Rebecca Goldstein has written a lovely biography of Gödel, for example. The other book that I was tempted to choose was Malachi Haim Hacohen’s incredible work of scholarship about the first half of Popper’s life, Karl Popper: The Formative Years 1902-1945, which goes from Popper’s birth in 1902 to the publication of The Open Society and its Enemies at the end of World War II. It’s the formative period in Popper’s life, before he became famous. It grounds Popper’s ideas in the milieu of Vienna and of the Circle. He’s very forgiving of Popper’s very difficult character—Popper was a notoriously difficult man. Because Hacohen regards him as a genius, he’s more tolerant of some of his character flaws than others have been. He goes too far, I think, in forgiving him for the way he treated other people.

Not unlike Ray Monk in his brilliant biography of Wittgenstein, who saw saintliness in what other people might just see as arrogance.

Yes, but with this difference: Ray Monk interprets Wittgenstein’s personality ‘issues’ as saintliness, or maybe eccentricity, or, more fundamentally, that Wittgenstein acted out of a sense of obligation to fulfil his brilliance. In other words, he gives them a good motive. Hacohen doesn’t go that far. He doesn’t say that it’s perfectly alright that Popper was a bully. He says that Popper’s behaviour should be put in context, and my sense is that he thinks it’s kind of irrelevant, given the weight of his genius. The other thing I would say is that Wittgenstein has a much stronger claim to the label of ‘genius’ than Popper. So, if you’re going to use the Hacohen excuse for personality weaknesses, then it’s better used for Wittgenstein than for Popper.

Let’s look at your last choice, Exact Thinking in Demented Times by Karl Sigmund.

I was aghast when this book came out. I was already several years into research for my own book. There was no decent biography of the Vienna Circle, and I was hoping that mine would be the first. And then this came out. So, I was a little depressed.

I was relieved by a number of things. Firstly, Sigmund is much less interested in the philosophy than I am. It’s a biography of the Circle and it does a little of what my book does. It’s partly about Vienna and it places the Circle in a Viennese context. But Sigmund is a mathematician and so, more than my book, it is about some of the puzzles and mathematical conundrums that some Circle members were interested in—Gödel in particular. There’s a lot in his book about somebody I barely mention in mine, David Hilbert, a celebrated mathematician.

“Logical empiricists have various enemies. But, really, a principal enemy is Heidegger”

It goes a lot into Gödel and his incompleteness theorems, which I cover only a little, although these theorems are fundamentally important in the history of logic. So, for anybody who’s interested in the mathematics and the logic of the Vienna Circle, this is a very good accompanying text to mine. I would say he’s slightly less interested in the culture than I am. I was very interested in what motivated the Circle and where they’d come from and their backgrounds and why they came to hold the positions they did. And I was particularly interested in what it was about the Circle that made them such a threat to the fascists and the Nazis. The Sigmund book closes in the late 1930s, whereas I was also interested in what happened to the Circle members after the war begins and they disperse. I’ve got quite a big section on that. So it’s a different kind of book, but complementary.

To round this up, it might be nice just to say what did happen to the Vienna Circle? Did it just fizzle out when the Nazis marched in?

‘Fizzle’ is a good word. People forget about the history of Vienna. It wasn’t the Nazis but the Austrian fascists, the Fatherland Front, who took over in 1934. And the Austrian fascists and the Nazis were separate parties, indeed competing forces.

The Austrian fascists were Austrian nationalists. The Nazis, of course, have a ‘Greater Germany’ foundation to their fascism. For those on the far right, the Austrian nationalists were a nationalist alternative to Nazism. When the Nazis came in following the Anschluss in March 1938, they took over, not from a democratic form of government, but from the Austro-fascists. Nonetheless, the logical empiricists were a threat both to the Austrian fascists and to the Nazis. When the Austro-fascists came to power in 1934, they effectively shut the logical empiricists down.

The Circle stumbled on, in a kind of dispersed form, until 1936, but already individual members were desperately trying to leave. An early member, Herbert Feigl, got away as early as 1931. Another important member of the Circle, Karl Menger, went to live in the United States. Otto Neurath had to flee because he was both a Jew and a Communist, and so doubly doomed. He escaped to Holland, then the UK. Schlick’s murder in 1936, though, was really the death knell of the Circle. They dispersed in many different directions. Popper ended up in New Zealand. Most of the rest made it to the UK or the US. I think only two members of the Circle stayed in Vienna and survived the war, keeping their heads down.

But the refugees in the UK and US breathed new life into Anglo-American philosophy. Circle members were now widely scattered and could no longer gather together. There was no Internet or Zoom. Different centres of logical empiricism sprang up, but the heyday was over.

But, intellectually, the aftermath was that the waves rippled out and the effect of this largely involuntary emigration was a kind of rigour and no-holds-barred approach to philosophy that had massive effects across the English-speaking world. I think its effects are still fairly clear. It’s in the same movement as Bertrand Russell’s focus on logic as the core of philosophy. But part of the energy behind analytic philosophy came from the dispersal of these very brilliant thinkers.

Yes, the importance of logic, the analysis of language, the role of empiricism. It’s almost impossible to imagine current analytic philosophy without the part played by logical empiricists and the way they spread their influence around the English-speaking world.

And I would still defend the spirit of logical empiricism. I remain suspicious when I hear somebody making a claim that doesn’t seem to have any connection with what can be tested or falsified!