In a recent short biography of Ernst Nagel, Yvonne Nagel mentioned the meeting of Nagel and Hosiasson in Warsaw during his stay there in the fall of 1934. She wrote:

Ernest also enjoyed meeting a younger couple—Janina Hosiasson and her fiancé the mathematician Adolf Lindenbaum. (A)

I have always placed the beginning of Janina and Adolf’s engagement much later than the fall of 1934, so this was news. When I asked Yvonne for the exact source of her assertion, she quoted a letter that Nagel wrote from Warsaw to his friend Sidney Hook, relating having met a certain Ms Hosiasson and her fiancé, who was a mathematician. No name of said fiancé was given. But in the context of what has been published about Hosiasson and Lindenbaum so far, it was a reasonable conclusion to draw: here we have some mathematician referred to as Janina’s fiancé, and she did end up marrying a mathematician by the end of the following year—so the man mentioned in the letter must be Lindenbaum.

But I could not shake the feeling that something in here was not hanging together with everything else I knew about Janina’s life.

As I mentioned, I was under the impression that the marriage with Lindenbaum came somewhat suddenly, and that the engagement itself was quite short. I do not currently have access to my whole library, so I cannot recover all my reasons here, but one of the things I remember that gave me that impression was the following quote from Otto Neurath, written when he had learned about the Lindenbaums’ death: “I remember how they met one another and gradually became accustomed to one another, e.g. in Paris.” (B) He meant here the Unity of Science congress in September 1935, which the (not yet) Lindenbaums attended together. The quote conjures an image of two people who are just getting used to being a couple, or maybe to being a couple out in the open. Which does not fit too well with the image of two people who had already been publicly together for at least a year.
But these are not hard facts, but impressions: both Neurath’s and mine. And I wanted to get as close to hard facts as I could.

First, I looked at all of the letters that Nagel sent to Hook from Warsaw (C), to see the full context of the quote above.

Nagel arrived in Warsaw on October 15, 1934. He immediately proceeded to make contact with the logicians. Two days later he wrote to Hook:

I have seen Łukasiewicz, Tarski and Lindemann for a brief space each, and to-morrow I have a date for a longer seminar with the former. (Nagel to Hook, 17.10.1934)

There was no logician Lindemann in Warsaw at the time (or, I suppose, ever?). The third man must be Lindenbaum. So, it seems that one of the first people Nagel met in Warsaw was Adolf Lindenbaum himself.

Warsaw did not agree with Nagel. He was feeling lonely and miserable, until, a week later, he made a new friend: Miss Hosiasson:

To-morrow I have a date with Frl. Dr. Hossiason [sic], wissenschaftlich of course, she is interested in probability and had an article in Mind a year or so ago. She was in England for eight months and knows a little English. (Nagel to Hook, 25.10.1934)

(Note the social signalling here—describing people and their potential worthwhile-ness in terms of their publications; we still do it, don’t we.)

One thing led to another—wissenschaftlich of course—and in the course of the following week Ernst finally had some nice people to spend time with in the cold bleak city (not my opinion, but his). On November 1 he wrote:

I think I wrote you I was to see Miss Hosiasson. I did, met her fiancé who is a mathematician, also a very good common friend who is a Dozent in physics. The latter two have a great admiration for Campbell and Bridgman, so I fell in with a sympathetic crowd. They also like music, and the physicist play [sic] the violin passably; he belongs to an amateur quartet, also plays duets with a lady at the piano, and I’ve heard them play. The physicist must be good, I can’t judge, but he had stuff in the Mathem. Annalen and rather first-class magazines. Jewish, of course, as is the whole group. With communist sympathies, but unable to stomach the dogmatism and bad manners of the Stalinists. (Nagel to Hook, 1.11.1934)

This is where we meet the fiancé. But this is also where my doubts begin. None of this goes too well with what we know about Lindenbaum. First, at this point Nagel had already met Lindenbaum, so being introduced like this for the second time makes little sense—would Ernst not write about the meeting in a different way if he had already had met the fiancé at the university? Second, Lindenbaum did not have much to do with physics. He took one physics lecture as a student: the one lecture that everyone took because the professor was entertaining. He did not publish anything on the subject. How likely is it that physics—and people’s favourite physicists—would be one of the main things talked about, or at least one of the things that made an impression on Nagel? Finally, the communism. Of all the left wing, socialist, or communist philosophers in the Warsaw group—Lindenbaum is the one known for being an actual supporter of Stalin (as opposed to his wife, who was very much not). So, another part of the description is shaky; although the last sentence in Nagel’s quote could refer not to “the whole group,” but only to the physicist, so there’s that.
I am very skeptical that the man described by Nagel is Adolf Lindenbaum. But who could it be then?

Could it be that the fiancé was Antoni Pański, Janina’s notorious previous partner and—they say—the love of her life?

Pro: Janina had been in a relationship with him since at least 1930. At the time she still lived with him on Koszykowa. He used to work for the statistics bureau of Warsaw, which—if you squint, and take into account that all this socialising with Nagel probably took place in boozy, smoky cafes—might make it plausible that Nagel would remember him as a mathematician.

Con: Yes, but we also know that the relationship ended somewhere in the mid-thirties. Maybe it was already dead by then. Yes, she lived on Koszykowa—in Antoni’s mother’s apartment, where Antoni also had lived—but actually, maybe he had moved out by then? I only have her address confirmed that year, not his. And finally: the jump from working for the statistics bureau to being introduced as a mathematician is not overwhelmingly convincing. Plus, it seems that 1934 was the year he was finally sacked from the statistics office job anyways.

Overall, not a great fit either.

How about trying to approach this from the other end: instead of going through the men I knew were in Janina’s life and matching them to the description by Ernst, why not look for someone matching the description first?

Enter Edward Poznański.

Born in 1901, Poznański studied intermittently at the University of Warsaw between 1920 and (at most?) 1929. His student records there do not contain any mention of degree examinations, giving an impression that he might have left without a Master’s or a PhD. (D) Over the years he took the usual mix of courses that comes to mind when we think of scholars of this group—a lot of logic with Leśniewski, set theory with Sierpiński, philosophy with Kotarbiński—but focused mostly on mathematics.
Mathematician: tick.

Poznański had a buddy, Aleksander Wundheiler. Poznański once described the two of them as one soul in two bodies (E). Together, they are now best known for their 1934 paper “The Concept of Truth in Physics” (F), published in the same volume as Hosiasson’s paper on the justification of induction. In the paper, they mention Bridgman and Campbell as the main source of influence and inspiration for their paper. If you want to know more, Artur Koterski and Thomas Uebel wrote a nice overview of what we know about Poznański and Wundheiler in terms of biographies—and gave some context to the 1934 paper (G).

Two good friends—one more of a mathematician, the other an assistant at a theoretical mechanics chair—who had just published a paper where they profess their admiration for Bridgman and Campbell: tick.

What about Poznański’s politics? I have nothing certain to report. The main non-philosophy thing I know about Poznański (for now) was his involvement with the Hebrew University in Jerusalem. While still in Poland, he was active in a society of Friends of the Hebrew University. A year or two before the war, Poznański left Poland for Palestine and worked as a librarian, philosopher, and the academic secretary of that university in the following decades. All of this is consistent with being left-leaning and anti-Stalinist, but does not prove it (we have a little bit of a Linda the bank teller situation here).

Additionally, there is the following bit of information about the whole group. During his 1930 stay in Warsaw, Carnap recorded the following in his diary of November 30:

(…) Nach 5h zu Tarski; seine Frau, Leśniewski, Łukasiewicz, Kotarbiński, Fräulein Sztejnbarg und Hosiasson, Lindenbaum. Mit Tarski und Hosiasson über die Ableitung der physikalischen Sätze aus den phänomenalen. Abends zu Fräulein Hosiasson mit Tarski, Sztejnbarg, 2 Physikern (Poznański und …). Diese beiden wollen die Physik auf der Koinzidenz aufbauen, sind sich aber über die Bedeutung eines Konstitutionssystems nicht ganz klar. (H)

Here we have an image of a group of friends who like to hang out at each other’s places and talk philosophy. At the time, Tarski, Hosiasson, and Sztejnbarg all lived in the same building on Koszykowa Street (I), so hopping from an afternoon at Tarskis to an evening at Fräulein Hosiasson must have been seamless. (Edward Poznański did not live on Koszykowa. His Warsaw address was Tłomackie 7, which happens to also be the address of the Great Synagogue of Warsaw, as his father had been an important rabbi. Casual. ) The second physicist, whose name escaped Carnap, sounds like Wundheiler, doesn’t he. It’s clear that Fräulein Hosiasson and Messrs Poznański and Wundheiler were friends even long before Ernst Nagel came to visit. It also looks like Mr Lindenbaum was also not too far away, incidentally.

Hence, here we have a mathematician (hard fact) who is a good friend of Wundheiler (hard fact) and of Hosiasson (highly probable fact), a fan of Campbell and Bridgman (hard fact) and maybe even not a fan of Stalin (half-wishful thinking). All of this is a much better fit to Nagel’s description than the previous two candidates. By inference to the best explanation, then, I would conclude that the man described by Nagel was likely Poznański, and unlikely Lindenbaum or Pański.

However, I would refrain from drawing any strong conclusions about the relationship status of Hosiasson and Poznański until I find any more evidence for such a thing.

To begin with, I get the impression that the word “fiancé” would be used around that time to refer to any “man friend” of an unmarried woman, whatever the exact status and seriousness of the relationship. Janina had already at the time lived together with a man without marriage: she was definitely not big on convention and tradition. There are also, of course, some more exaggerated interpretations of the whole situation. After all, the 1920s were a great time for casual romance, partner swapping, keeping a husband in the country and a lover in the city, etc. (I will be writing more about all that one day, through the eyes of one of Janina’s schoolmates.) Who knows, maybe there were three fiancés. Or two. Or none. For now, I say we just don’t know.

With the detective work concluded—for the time being—there remains a question of what was it all for. I will come back to it in the next instalment.

Footnotes and references

(A) Nagel, Y. (2022). Ernest Nagel: A Biography. In: Neuber, M., Tuboly, A.T. (eds) Ernest Nagel: Philosophy of Science and the Fight for Clarity. Logic, Epistemology, and the Unity of Science, vol 53. Springer, Cham, 35.

(B) Otto Neurath to Rudolf Carnap, 24 Sept 1945, Box 102 Folder 55, Rudolf Carnap Papers, 1905-1970, ASP.1974.01, Archives of Scientific Philosophy, Archives & Special Collections, University of Pittsburgh Library System.

(C) They are all in Box 22, Folder 8 of the Sidney Hook Papers, Hoover Institution Library & Archives. All citations from there.

(D) Additionally, in the list of attendees of the Third Polish Philosophical Congress in 1936, Poznański is listed without any academic title.

(E) Edward Poznański to Otto Neurath, 4 April 1934, Folder 285, Otto Neurath Correspondence, Wiener Kreis Archiv, Noord-Hollands Archief.

(F) The English translation: Wundheiler, A., Poznański, E. (2017) The Concept of Truth in Physics. In: A. Brożek et al. (eds.), The Significance of the Lvov-Warsaw School in the European Culture, 309-346.

(G) Koterski, A., Uebel, T. (2017). Poznański and Wundheiler’s ‘The Concept of Truth in Physics’: The Lvov-Warsaw School Contribution to Encyclopedism. In: A. Brożek et al. (eds.), The Significance of the Lvov-Warsaw School in the European Culture, 291-307.

(H) Carnap, R., Tagebücher Band 2 | 1920–1935. Herausgegeben von Christian Damböckunter Mitarbeit von Brigitta Arden, Roman Jordan, Brigitte Parakenings und Lois M. Rendl. Felix Meiner Verlag GmbH, Hamburg 2022, 495.

(I) I am not 100% certain about Tarski anymore, there are some inconsistencies between some documents I have seen in the archives and the Feferman&Feferman biography. But that’s for another time. I’m also not in the business of dating Tarski’s addresses precisely, I leave that to his own biographers.