Building a New Thursday Circle Carnap and Frank in Prague

In 1949, Philipp Frank claimed that he and Rudolf Carnap built up a new center for the scientific world conception in Prague between 1931 and 1935. The aim of this paper is to provide historical evidence and further materials to approach this claim of Frank. Definite answers, however, require more space and contextualization, so I will just sketch some partial but hopefully promising narratives and rudimentary answers. I claim that though Carnap and Frank indeed tried to build a new center, they were unsuccessful, and possibly there were many reasons for this. This is the general claim; regarding Carnap, I will also show his way to the German University of Prague and his philosophical, scholarly, and cultural life in Prague.

Reichenbach for one of the chairs; so Reichenbach indicated to Schlick that in such a case Carnap should get the Prague job (though he is still only the second on the job-list). 11 Two years later, in 1930, replying to Schlick, Reichenbach wrote that the Prague-case is still not decided: though he wants to go there, there are financial issues. 12 In October 1931, now six years after the beginnings and first letters, Schlick wrote that he hopes that Reichenbach is not sorrowful because of Prague and that Carnap will have a nice time there. 13 In response, Reichenbach claimed that he is actually quite sad about the Prague job, but he had to decline the offer! He had no choice, as he said, since he had to take care of the existence of his family and this was not made possible by the economic situation in Prague. 14 Though there are no details in the letter, we find some hints in Carnap's correspondence. But the point is made: Carnap was only second and thus he was able to go to Prague because Reichenbach declined their offer, he was not chosen as the first candidate! 15 Carnap got a letter from Prague on June 19, 1930: as his diary entry indicates from the next day, it was about some special terms (Bedingungen) that Neurath suggested to accept: Carnap would become a professor extraordinarius with the title of a professor ordinarius. The decision was made quite hard for him since on June 21, 1930 "Schlick telephoned: title of professor in the faculty has been accepted (39 against 5)." 16 So Carnap became a professor in Vienna! In August, he met Reichenbach and they talked about Prague. The latter said that Frank and Heinrich Freiherr Rausch von Traubenberg, professor of physics in Prague, were not inclined to create a professor ordinarius position, because they want a second position in mathematics. Reichenbach seemed to suggest Carnap to accept temporarily the non-ordinarius position with the condition that it will be later transformed into an ordinarius one. 17 On September 2, 1930, Carnap went to Prague and met in the Ministry Dr. František Havelka, and the "Prodekan" and plant physiologist Ernst Pringsheim to discuss the issues concerning the new job. Frank indicated that Traubenberg was impatient because the negotiations with Reichenbach were too long: they indicated that Carnap has to decide quickly. 18 It is not known from the documents when did Carnap accept the job-offer with their conditions, but he got to know in August 1931 that he was appointed already on June 30, though it did not become legally valid [rechtskräftig]; it still wasn't in late October, when he started to teach, or in December, when he wrote his first longer report about Prague. 19 He was just an assistant (Supplent), not a professor, even in the next semester, in March 1932: 20 that meant that his salary was quite reduced. The ministry told Carnap in 1932 that everything was in order and only translational things were to be done; he was skeptical though, and with good reasons! He noted in his diaries that when he came back to Prague from the 1935 Paris Congress, Dr. Havelka claimed, "the promotion to Ordinarius has a good chance, but the earliest date is January [1936]." 21 Since Carnap left Prague in December 1935, he never became actually a professor ordinarius there.
What conclusions and observations shall we draw from these data? (1) During the 1920s, Reichenbach was much more respected and wanted in philosophical circles than Carnap: until 1926, Reichenbach published two monographs (Relativitätstheorie und Erkenntnis apriori, 1920; Axiomatik der relativistischen Raum-Zeit-Lehre, 1924), his doctoral dissertation in Zeitschrift für Philosophie und philosophische Kritik (1915) and more than twenty articles, mainly in physical journals. On the other hand, Carnap published his doctoral dissertation and two articles in Kant-Studien, another paper in Annalen der Philosophie und philosophischen Kritik, and finally a short monograph about Physikalische Begriffsbildung (1926). Hence, even if Reichenbach's wider recognition is understandable, we have now also some more evidence about its effects as well.
(2) The considerations in this section about Carnap's struggle also suggest that he did not simply continue his philosophical career and projects in Prague after Vienna, but was quite lucky that he had lower requirements and existential needs than Reichenbach, and that the latter declined an offer he actually really wanted to take. It would be a quite interesting counterfactual history, especially for the history of philosophy of physics, namely, what would have happened if Reichenbach joins Frank in Prague already around 1928 when he was just about to publish his Philosophy der Raum-Zeit-Lehre.

WS
(1) Logik II. [5, then 2] (2) Kritische Geschichte der Philosophie der Neuzeit  What can be seen from this list? First of all, the depressingly low number of students is telling. Carnap marked with an exclamation mark the 44 participants of the Naturphilosophische Strömungen der Gegenwart lecture in the 1933 winter semester. Though he did not give a number in the diaries, he emphasized the fact of the numerous participants of the Logik I lecture in the 1932 winter semester. All the other lectures and seminars were rarely attended. The typical entries in the diaries about these lectures registered an average of 5 students, though usually, Ina was one of them.
What is even more striking is the comparison of Prague to Vienna: in his circular letter (Rundbrief), Carnap noted that he has the same Einführung in die wissenschaftliche Philosophie course that he had already in Vienna for years. The only difference is that while 14 students attended it in Prague, he had 150 "registered participants" in Vienna. 24 But as he noted in his diaries, with time, that 14 became occasionally just 4. Since these numbers did not change in any positive manner during his five years stay in Prague, Carnap noted the inclination of the students to participate at his courses with sadness, bitterness and at times anger.
We would have a clearer picture if we were to know the exact number of students enrolled at the universities in Prague and Vienna. It is quite possible that the number of students at Carnap's courses in Prague in relation to the number of students at the University is not that depressing after all and we should put a different weight on the numbers above. Nonetheless, what matters now is Carnap's own perspective and he experienced the situation quite sadly: even if the ratio of his students to the students enrolled at the University was promising, working now with 5 students instead of talking to 150 might came as a loss of prestige in his perspective.
Some of Carnap's lecture notes are preserved in shorthand, transcript or typed forms. Instead of going through them individually, I just note that Carnap had such lectures that were connected somehow to his research, and did not start ahead anything entirely new. While this might not be surprising, it also points to the fact that we should look into Carnap's work outside the seminar rooms.

The Thursday Colloquium(s)
In 1999, Gereon Wolters wrote a quite pessimistic paper about logical empiricists' philosophy of biology: he claimed that logical empiricists did not have any proper, deep, or relevant philosophy of biology since wrong people asked the wrong questions in their wrong (highly ideological) frameworks.
In 2015, Wolters gave a talk, actually a refined and revised version of his 1999 paper. Though the general outlook of the new one is the same, Wolters noted the important efforts of (at least some) logical empiricists to deepen their knowledge in the philosophy of biology. By discussing the Prague "Vorkonferenz" with the Paris/Copenhagen Congresses, Wolters (2018) argues that "[…] from 'Prague', via 'Paris' to 'Copenhagen' we see a sort of positive gradient as to special problems in the philosophy of biology: It goes from zero in Prague via old questions in Paris to information about actual biological science, inviting philosophical analysis in Copenhagen." In order to facilitate his arguments and points, Wolters recalls some lectures of a Colloquium, organized by Frank and Carnap at Prague in 1935. Actually, this is the only reference to Carnap and Frank's Colloquium in the literature that I am aware of.
Before I discuss this Colloquium, I have to note that actually, the cooperation of Carnap and Frank dates back to as early as 1932. 25 In one of his first report-letters about Prague, Carnap wrote to Schlick on March 2, 1932, that he "started a Thursday-night-circle [Donnerstagabendzirkel] with Frank." We do not have much information about this group: Carnap wrote that there were especially many Russians and followers of the Brentano-school, who are capable of discussing problems rationally and deliberately. In the letter, we found that their issue was Carnap's (1932Carnap's ( /1959) "Metaphysics" paper, presumably the "Überwindung" one that was published already. 26 The "first session" of the Circle (called by Carnap in the diaries as "our Circle") was on January 14, 1932 at Frank's place, with the following participants: Ina Carnap, the Russian Georg Katkov and Walter Engel, both of whom belonged to the third-generation of the Brentano-school; Sergius Hessen, a Russian philosopher and educationalist, one of the founders and editors of the international journal Logos and a neo-Kantian dialectician by education. Another participant was presumably Felix Weltsch, a close friend of Franz Kafka, and a well-known organizer of Jewish life in Bohemia, having two doctorates, one in law and one in philosophy. Finally, there was Karl Reach, a student of Carnap who attended many of his lectures and is known for a paper on the name relations and logical antinomies published in The Journal of Symbolic Logic (1938). Carnap noted that while Katkov and Weltsch understood well his points, Hessen did not get much of it; unfortunately, the latter led the discussion, "debating violently." 27 According to the diaries, the Circle did not work out well since it had only three more sessions. On January 21, they had an "interesting" meeting: the mathematician, Karl Löwner, who became worldwide known later at Stanford as "Charles Loewner", was also there and made "clear remarks" but that is all that we know. One week later (January 28) Carnap noted a "Colloquium" with discussion about syntax without any further information about the details. Finally, again one week later, on February 4, Carnap became "impatient with Hessen", even though Frank tried to mediate between them: Carnap explained that he does not think anymore that it is possible for them to understand each other. 28 Since nothing is indicated in Carnap's diaries or letters about the Circle, a Colloquium, or about regular meetings and discussions, seemingly Hessen's temperament and incomprehension have brought the First Prague Circle to an end.
A few years of silence were ahead of Carnap and Frank on this front. After Carnap's lectures in London, the appearance of Logische Syntax der Sprache and the famous preconference, Carnap noted in his diaries in November 1934 that Frank wants to talk about the logical problems of quantum mechanics with others: besides discussing special questions of matrix operations and various formulations of the theory, Frank meant that "this would be a good test for the fruitfulness of scientific logic [wissenschaftliche Logik]." 29 A few months later, on February 9, 1935, Carnap wrote that "Frank by us. Plans for a Colloquium." 30 And indeed that is what they did. A month later came the first session. The group was called "Colloquium for the Philosophical Foundations of Natural Sciences." As the theme of the 1935 summer semester, they choose the questions of "Physics and Biology." 25 There is no indication yet of Frank's having an own circle without Carnap, or before Carnap's arrival. Since most of Frank's paper from this period have been destroyed or lost, we have to rely on secondary materials, but none of them suggested so far that Frank would have organized anything; quite the contrary, as we will see. 26 Carnap to Schlick, March 2, 1932 (MSN). 27 Carnap's diary entry, January 14, 1932. On the Brentano-school see the essays in Kriegel 2017; on the life and works of Hessen see Hans 1950. 28 Carnap's diary entry, February. 4, 1932. 29 Carnap's diary entry, November 30, 1934. 30 Carnap's diary entry, February 9, 1935. Frank, as the first speaker, talked on March 18 about "what do the new theories of physics mean for boundary questions of physics and biology?" Among the discussants we find, for example, Joseph Gicklhorn who was, first of all, a biologist, with an interest in the human sciences and history; in February 1931, before Carnap went to Prague, Gicklhorn held a lecture in the Verein Ernst Mach about cell physics. 31 Another participant was Johannes Paul Fortner, a zoologist; Reinhold Fürth, who was an experimental physicist, studying with and working next to Frank for almost fifteen years; 32 Ludwig Berwald, professor of mathematics, working on geometry; and Karl Löwner.
According to Carnap's diaries, there were eight more meetings. One week later (March 25) Frank talked again, but this time Ernst Pringsheim was also there with Kostja Zetkin, a German physician, social economist, and lover of Rosa Luxemburg. Zetkin, after fleeing from Moscow, worked as a physician in Prague between 1935 and 1938.
At the next meeting (April 1), Gicklhorn presented a lecture: the new participants were Trude Schmidl-Waehner, an Austrian painter, and the Viennese biologist Felix Mainx, who wrote later about the Foundations of Biology for the International Encyclopedia of Unified Science. A certain Dr. Keller and Hans Zeisel were there as well: the latter was a sociologist and legal scholar from Vienna whose memoirs of Carnap were published posthumously (Zeisel 1993).
At another session (May 13) Pringsheim talked about whether "biology has its own laws"; as Carnap noted in the diaries, he criticized different things in the presentation with Frank and Fürth. The fifth occasion was Carnap's lecture (May 27): "The relation between biology and physics, from the viewpoint of the logic of science". As it was claimed in the diaries, Pringsheim and Adolf Pascher, director of the Institute of Botany, were sympathetic to the presentation, while "Gicklhorn thought, 'too much physics'".
The next two meetings (June 6 and 10) were just mentioned in the diaries, but nothing was said about them. The final two occasions, held in the next semester, were devoted to Mainx (who talked about genetics, November 11) and to Fürth ("Are the physical processes continuous or discontinuous?", December 2). The lecture was followed by a discussion about probability and wave function between Carnap, Frank, Fürth and presumably Paul Hertz, a German philosopher of science and physicist, who was emigrating from Nazism first to Switzerland, then to Prague. (Hertz was actually the co-editor of Helmholtz's (1921Helmholtz's ( /1977 epistemological papers with Schlick.) What follows from these considerations? (1) There were only a few scholars who attended the small number of meetings; these scholars were indeed working on biology and physics, so the group could fulfill its task of investigating the relations between physics and biology. This could also support Wolter's claim that this group was initiated to get a closer look at (the philosophy of) biology.  indeed gave a talk on the relation of physics to biology at the 1935 Paris Congress; one year later at the Second Congress in Copenhagen the topic was "The Problem of Causality -With Special Consideration of Physics and Biology." 33 (2) What is also salient is the wide range of intellectuals, attending the Circle: painter, physician, physicist, biologist, mathematician, sociologist, zoologist, and botanist. It would be again a piece of counterfactual history-writing to imagine what would have happened if Carnap and Frank have more time and energy. But before we would be too optimistic or sentimental, note that in 1935 Neurath asked Carnap in a letter whether something came out of the colloquium and anyone could deliver a talk at the forthcoming Paris congress. Carnap 31 Carnap's diary entry, February 18, 1931. 32 Fürth (1965 gives some impressions about his Prague time with Frank. 33 On the congress see Stadler 2001s and logical empiricists' philosophy of biology is taken up in Hofer 2002 and said in his reply that unfortunately only Frank and he would be able to do that; he also mentioned Gicklhorn but claimed that he could not emphasize well the theoretical questions of the logic of science. 34 Considering the fact that next year Carnap emigrated to the United States, and two years later Frank followed him, one might plausibly claim that the discussion group was not able to achieve anything similar to the Vienna Circle and Frank could not build a functioning school or center with Carnap in Prague. 35 Discussion groups and circles were quite regular, however, in Prague (similarly as they were in Vienna): both cities presented a certain "culture of circles". Prague had its own Philosophy Circle (Cercle philosophique de Prague), directed by such pupils of Edmund Husserl as Ludwig Landgrebe and Jan Patoćka. After Husserl became their honorary member in May 1935, he delivered a lecture in November about "The Crisis of European Sciences and Psychology". Carnap noted in his diaries that he did not attend Husserl's lecture, though it attracted Felix Kaufmann from Vienna. 36 Besides the Philosophy Circle, there was a linguistic circle (more on below), and the Brentano Association, hosting the Brentano Nachlass. These groups, associations and circles, having numerous members and sympathizers, were not entirely hostile to logical empiricism, though they expressed more criticism than support.
Actually, neither Frank, nor Carnap could function as the "big locomotive" of the alleged "new center in Prague", thus they were not able to develop any unified or recognizable brand. If Carnap and Frank had any recognition in Prague, they had it through Vienna's Vienna Circle. 37 Carnap (1963a, 33) said in his famous intellectual autobiography that "[m]y life in Prague, without the [Vienna] Circle, was more solitary than it had been in Vienna. I used most of my time for concentrated work, especially on the book on logical syntax." According to the diaries, Carnap indeed spent most of his time and energy on the syntax manuscript. He worked, however, in relative isolation: he was invited to the Linguistic Circle of Prague by Roman Jakobson only in February 1935, and he delivered a talk about "Logische Syntax der Sprache" three months later, so only after the publication of the Syntax book. 38 There is no evidence of any earlier direct contacts between Carnap and the structural linguists of Prague, though their circle was very similar to the Vienna Circle: they even had their own journal and manifesto from 1929 to propagate their modernist worldview. 39 Carnap was more active, however, in the Mathematical Circle (Mathematisches Kränzchen), where he presented three lectures (one on Hilbert, another on Gödel, and one about general axiomatics) and attended many others. 40 34 Neurath to Carnap, May 11, 1935 (RC 029-09-55) and Carnap to Neurath, May 15, 1935 (RC 029-09-54). 35 While seemingly the discussion group on physics and biology did not have a major impact on Carnap as a philosopher of physics and biology, Uljana Feest and Thomas Mormann argue further in the present volume that Carnap was unsuccessful also as a philosopher of psychology. 36 Carnap's diary entry, November 15 and 16, 1935. 37 It should be mentioned, however, that many philosophers visited Prague during these years: W. V. O. Quine, Alfred Tarski, and Carl G. Hempel, just to name a few. Nonetheless, these scholars went there especially because of Carnap and not because of an internationally well-recognized school or center, as it often happened in the case of the Viennese Vienna Circle. 38 See Carnap's diary entries, February 11 and May 20, 1935. 39 On Prague's linguistic circle, see Broekman 1974. 40 See Carnap's diary entries, January 15, 22, February 5, November 25 1932 andJanuary 19, 1934. But Logische Syntax was not the only publication of Carnap during his Prague period, and so the question arises, what was Carnap working on, and whether we could detect any special influence on his thought that emerged particularly during the Prague-time? 41 Some of the most famous papers that appeared around 1931 and 1932 were written before Carnap moved to Prague. Among these, we find "Überwindung der Metaphysik", the "Die Physikalische Sprache als Universalsprache," and the "Psychologie in physikalischer Sprache". Though Carnap's response to Edgar Zilsel and Karl Duncker were written in Prague, it was composed in the first months (his "Protokollsätze" paper a bit later), so nothing particularly influential could be detected there.

Carnap's Philosophical Life
Besides some reviews, there is nothing from 1933. Among the publications from 1934, we find "On the Character of Philosophic Problems," which was written especially for "America" and is based on Carnap's Swedish andDanish lectures from 1932 and1933. 42 Obviously, there is the Syntax book, some minor writings on pragmatism, mathematics, but also his volume for Neurath's Einheitswissenschaft, the English translation of his "Physikalische Sprache" paper, and the lesser-known "Theoretische Fragen und praktische Entscheidungen." The latter ends with an interesting passage, claiming that metaphysics has no theoretical content, thus cannot be refuted in the strict sense, but can be studied […] through investigations of a sociologist and a psychologist; one can determine, for example, that it is here a matter of wish fulfillment and similar things, whose systematic advancement and diffusion in social struggle serves as a diversion and a smoke screen.
In order to avoid misunderstanding, it should here be remarked that we are not speaking here of a conscious goal but rather of the factual social function, which in the main does not come into the consciousness of the practitioners but is rather hidden by a justifying ideology. (Carnap 1934, 259-260.) This passage might sound as Carnap has learnt the lessons of Frank about the sociological determination of theories and metaphysical ideas. But "ideology" as some form of "false consciousness" is much closer to Neurath than to Frank: the latter's 1932 book on causation did not consider explicitly the question of ideologies and even later, Frank's concept was related rather to Karl Mannheim and Robert Merton than to Marx. Nevertheless, Carnap's diaries testify that he was aware of the Marxist notion of ideology through various lectures, reading groups, usually advocated by Neurath, and also spoke often with the Marxist Walter Hollitscher. 43 In 1935, Carnap published his London-lectures as "Philosophy and Logical Syntax," a paper on psychology and the philosophy of mind in French (presented at a Paris symposium on psychology and the natural sciences), another mathematical passage that was cut from Syntax, and his 1934 Prague Vorkonferenz paper, "Formalwissenschaft und Realwissenschaft".
Again, what do these publications show to us? Carnap was working indeed on his Syntax book, and many of his publications were related to that project. Though he noted later 41 It should be mentioned, though, that there is a file in the Carnap Archive at Los Angeles (UCLA 03 -CM10), entitled "Einführung in die wissenschaftliche Philosophie," on which Carnap worked for years (seemingly between 1929 and early 1931) before his Prague-time. Besides a few pages of something like an analytic table of contents for two volumes, the file consists mainly of 150 pages of shorthand notes. Some of which are dated as "November 1931," so presumably was using this material for teaching the "Einführung" course in Prague as well. The text is a sort of introduction into scientific philosophy, summarizing the main issue of the early 1930s: overcoming metaphysics, foundations of the special sciences (empirical and formal as well); the first volume was titled as "The Language of Science," while the second as "The Foundations of the Sciences." I am grateful to Christian Damböck for calling my attention to this file. 42 See Carnap's diary, November 14, 16, 18, 1932 andJune 24, 1933. 43 See for example the diary entries from May 12, 1930;April 18, 1931 andJanuary 2, 1934. Note that the first entry dates before his departure to Prague. that he has learnt a lot from Frank about the philosophy of physics, he did not present anything particularly relevant about that in his publicationsneither about the philosophy of biology. While Logical Syntax has a few passages about these questions, they are quite general and optimistic regarding the project of unified science. Nevertheless, though these discussions with Frank and in their circle(s) did not surface in his writings, Carnap might have been motivated in his unified science conception that emerged later with renewed force in the Encyclopedia.
With regard actual philosophical works, Carnap (1963a, 39) complained that while in Vienna he could talk at least with the members of the Circle, in Prague he "had even fewer opportunities for discussions with philosophers," since he belonged to the Faculty of the Natural Sciences and not to the Humanities. (As Frank (1949, 45) noted, it was through Tomáš G. Masarykan influential philosopher, sociologist and the first President of the new Czechoslovakia after World War Ithat the Faculty of Sciences created a professorship for natural philosophy. 44 ) But there are some indications that the Faculty of Natural Sciences had some previous relations to philosophy . Frank (1947, 77-78) noted in his Einstein biography, that the life goal of the famous physicists Anton Lampawho brought Einstein and Frank to Prague -was to "propagate Mach's views and to win adherents for them." Though Lampa left Prague for Vienna in 1918, his influence on the scientific community is unaccounted so far and, on the other hand, with Frank's appointment, disseminating the ideas of Mach was continued. Therefore, before World War I (and possibly even after it), Mach's philosophy was still prevailing among natural scientists -it wasn't necessary thus that Carnap could not talk about philosophy at his Faculty.
Nevertheless, as soon as his Vorlesungen and Seminare were over, Carnap got on the train and lectured around Europe, seeking out old and new connections. Going through Berlin (talking at Reichenbach's seminar and lecturing on the radio), he went to Copenhagen, Göteborg and Stockholm (1932), later to Bratislava and Brünn (1934). Next year he visited Münster to meet Heinrich Scholz and talk about the philosophy of mathematics. These various presentations picked up the questions of the nature of philosophy (which he called in Brünn as the "opium of the intelligentsia"), of soul and god (a related lecture was published recently by Thomas Mormann, see Carnap 1929Carnap /2004, and of the natural and human sciences. While he talked in Prague about "the way of scientific philosophy" in the Urania (Prague's German Society which aimed at communicating scientific results to a broader public), he also touched upon the "sociological function of metaphysics in the present" at the Society of Socialist Academics. There might be some connections to Frankgiven that this was one of the latter's most favored topics during his entire careerbut the talk is not preserved, unfortunately.
Regarding the line of personal influences, we must strictly distinguish the Carnap-Frank andFrank-Carnap routes. Frank's The Law of Causality andits Limits (1932/1998), published in 1932, contains general references to Carnap occasionally, mainly with regard to his investigations into the connection of metaphysics to realism. This is not at all surprising: Carnap's (1928Carnap's ( /2005  von Mises, Ernst Schrödinger), of biologists (Josef Gicklhorn and Fritz Knoll), 46 of sociologists (Neurath), but not to philosophers and not to Carnap. A few years later, however, Carnap became quite effective in moving Frank into new directions. After the appearance of the Syntax-book, Frank often referred explicitly to Carnap's book (1938Carnap's book ( /1949/1953 and to the logic of science (1934/1949, 124). This does not mean that Frank started to pursue logical and syntactical inquiries: but his remarks show the signs of Carnap's influence. Frank admitted the legitimacy of Carnap's approach: he even planned a lecture, about 'logical syntax and physics' for the 1938 Cambridge congress, but canceled it; 47 furthermore, he tried to integrate that type of investigation into a more general philosophy of science, what was called recently by Thomas Uebel (2012) as the "bipartite metatheory".
Regarding the Frank-Carnap line, note first that Frank was significantly honored among logical empiricists and other circles as well. (Though this may not be obvious in the Circle's published writings, the correspondences of the individual members testify this.) Many of Frank's papers were translated into French, as soon as they were published in German, just like his pamphlet -entitled "The Fall of Mechanistic Physics" )that was written for Neurath's Einheitswissenschaft. This booklet, though it is not mentioned in Frank's bibliography (in Frank 1932/1998, was translated into Czech after its publication (Frank 1937).
Therefore one might expect some direct and significant influences here. Even though Carnap and Frank met regularly when they were in town at the same time (actually this did not happen very often), Fürth (1965, xiv) claimed that " [Frank] preferred to work on his own and never had a 'research school.'" But this does not mean that Frank's work did not have any impact on Carnap's thoughts. Carnap (1963a, 32) claimed, for example, in his intellectual autobiography that "in a way similar to Neurath, [Frank] often brought the abstract discussion among the logicians back to the considerations of concrete situations.
[…] I received many fruitful ideas from my talks with him, especially on the foundation of physics." Frank indeed had some slight effect on Carnap: he noted in his An Introduction to the Philosophy of Science that according to Frank, "it is often instructive to read the prefaces of scientific textbooks" (1966/1995, 206). Though Carnap discussed an example of how the sentence "nature never violates the laws" documents extra-scientific tendencies, he did not provide details or context, only admitted the legitimacy of such inquiries.
But that book of Carnap, which is rarely discussed besides its considerations on scientific realism and instrumentalism, might contain some surprises. Carnap presents there his ideas on many important notions of philosophy of science, and devotes some space to quantum physics as well. Since he was a trained theoretical physician, he had a good position to write about such issues, but the truth is, he wrote to Wolfgang Yourgrau in 1958, that he is not that familiar with quantum mechanics since during his education he learnt about the theory of relativity, and later he turned towards mathematics and not followed the newest debates in and about physics. 48 Thus it would be important to contrast what Carnap says in this book about physics and what Frank wrote during the 1930s to see whether there is any line of influence there. Again, before we become too optimistic, note that Carnap claimed in his diaries, that just a few days before he left Prague, he was able to tell Frank, after waiting 46 Knoll was an Austrian botanist who became professor in Prague after 1922 andlater in Vienna (1933). He was also a member of the NSDAP and was known later for his national socialist views. According to the diaries, Carnap met Knoll once in Prague on December 12, 1926. 47 Frank to Neurath, June 1938. 48 Carnap to Wolfgang Yourgrau, October 3, 1958 (RC 027-42-03). Actually, Carnap mentioned this also in his intellectual autobiography (1963a, 14-15), where he claimed that Reichenbach used to help him in physical questions and in turn he helped Reichenbach in logical problems. for four years, an idea about the gravitational field. This does not sound like a well-balanced relation between them. 49 Carnap knew well Frank's major work: after the appearance of The Law of Causality, he (1933, 275) quickly reviewed it in Kant-Studien. His remarks are not very interesting in themselves: he does not criticize the book or picks up any particular point to develop further. He notices the conceptual crisis of physics and appreciates Frank for his exact and clear formulations, for his inclination to write for the laymen, and calls the book as the "best contemporary presentation of the causality-problem." He also emphasized that Frank does not admit any philosophy beyond the sciences as a separate higher discipline.
Though the review is quite regular, Carnap and Frank were obviously approaching philosophy, science, their nature and function from the same ground and they reached very similar conclusions. Nonetheless, the abovementioned "bipartite metatheory conception" was lurking around that time. Carnap wrote in Logische Syntax that theory of science "in addition to the logic of science, includes also the empirical investigations of scientific activity, such as historical, sociological, and, above all, psychological inquiries" (1934/1937, 279). Frank's book contained many interesting chapters on the historical and sociological conditions of scientific, especially physical and philosophical theories, a fact acknowledged and stressed in Carnap's review as well. 50 Nevertheless, Carnap was either a philosophically minded physicist and logician or a philosopher trained in the natural sciences, he certainly was not a sociologist of science. As he said (1963b, 868) later: "unfortunately a division of labor was necessary, and therefore I am compelled to leave the detailed work in this direction [the analysis of the social and cultural roots of philosophical movements] to philosophically interested sociologists and sociologically trained philosophers."

Carnap's Personal and Cultural Life
It is known from the original manuscript of his intellectual autobiography, that Carnap "missed painfully" that spirit and attitude in Vienna, which he encountered in the German Youth Movement. "Although [Carnap] was able to play a leading role in the philosophical work of the [Vienna Circle, he] was unable to fulfill the task of a missionary or a prophet." The United States is also mentioned: he faced similar troubles there, but nothing is said about Prague. 51 Presumably, this is not accidental. Carnap was leading no one there: as we saw, he did not have a secured circle or group of regular students and he was not a public intellectual or cultural organizer.
It is also possible that Prague offered more possibilities when Frank started to work there: for example, around 1911 and 1912, the house of Berta Fanta provided the place for the so-called Fanta-Kreis (it is also known as "Café Louvre" after its first residence). Fanta was a well-known Jewish intellectual figure in the life of Prague, who was much interested in German and Czech literature, science, and arts, organizing thus a forum for the cosmopolitan elite outside the academic curriculum. Prague's most prominent scientists and artists attended the meetings, which took place before World War I: Albert Einstein, Christian von Ehrenfels, Oskar Kraus, Franz Kafka, Max Brod, Rudolf Steiner, Hugo Bergmann, and Gerhard Kowalewski. They talked mainly about philosophy, religion, but there were also musical performances. According to many sources, Frank attended these meetings as well. 52 Nevertheless, Berta Fanta died after World War I, and her circle was not continued, though presumably, something like that would have kept Carnap busy as well. Though it 49 Carnap's diary entry, December 7, 1935. 50 On Frank's sociology of science, see Uebel 2000 andTuboly 2017. 51 Carnap, 1957, UCLA, Box 2, CM3, folder M-A5, pp. B35-B36. 52 See Wein 2016, 54;Smith 1981, 141. n.9.;Pawel 1984, 145. See also the autobiography of Gerhard Kowalewski (1950). should be mentioned that Carnap could have withdrawn from cultural life given the newly emerged unsupportive atmosphere of the 1930s. In the section on "Values and Practical Decisions" of his Library of Living Philosophers volume, Carnap (1963a, 82) described how Oskar Kraus, the famous Brentano-scholar of Prague, "seriously pondered the question whether it was not his duty to call on the state authorities to put [him] in jail. " Carnap claimed in the early 1930s that ethical, normative and other types of value statements do not have any theoretical or cognitive content, empirically and intersubjectively approachable by factual scientific investigations. They were meaningless given a very restrictive sense of "meaning" and Carnap always made this explicit. He (1963a, 81) also admitted that these sentences have "emotive or motivating [components and meaning], and their effect in education, admonition, political appeal, etc., is based on these components." Nevertheless Carnap was criticized by different persons, who "ascribed to the problem of the logical nature of value statements an exaggerated practical significance" (ibid.). They said that by not having theoretical, thus demonstrable content and validity, value statements lost their true interpretation and this conception leads to immorality and nihilism. As it turned out, Kraus had this problem with Carnap's conception at his seminar and after that he aimed at bringing this issue to higher authorities in 1935. 53 When Kraus and Carnap met personally, they were able to find a common ground: it turned out that Carnap was not a "wicked man" and he developed a "very high respect for [Kraus'] sincerity and absolute honesty in philosophical discussions, and his kindness and warmheartedness had a great personal appeal" (1963a, 82). 54 From Carnap's personal life one thing should be mentioned. Carnap and Ina's civil ceremony was on March 5, 1933 and the Frank's were their legal witnesses. I quote Isreal Scheffler who described Carnap's wedding and Frank's role in it as follows: [Frank served] as a witness at the wedding ceremony of Rudolf Carnap and his wife. The ceremony was conducted in Czech, which Carnap did not understand. Frank therefore acted as translator as well as legal witness. He had to convey the official's questions to Carnap in German, and then translate his answers into Czech for the official to meet the formal requirements of the rite. When the procedure began, Carnap, the meticulous logician and philosopher of language, asked Frank to clarify the meaning of the verbal formulas required. As the procedure continued, Carnap kept interjecting questions as to the logical status of the particular statements he was expected to supply at each juncture. Frank finally interrupted him, saying, in effect, "Do you want to get married or not? If so, just answer and don't ask questions!" (Scheffler 2004, 66.) Carnap wrote to Schlick that the ceremony was insignificant for them: 55 they were living together for many years, and the marriage played presumably more of a pragmatic role with regard to future traveling, for example. Nevertheless asking the Franks as their legal witnesses may point towards that Carnap's cultural and personal life in Prague was mainly concentrated around the Franks: Philipp Frank often translated Russian movies for the Carnaps in the cinema, and the Carnaps often visited the Franks, even when Philipp was out of town.

Conclusion: On the Road Again
53 Kraus presumably had an even deeper problem with logical empiricists. Herbert Feigl (1969, 7) told the following story later: in 1920, when Einstein was again in Prague to hold a lecture, Kraus debated him "with great excitement," arguing for the synthetic a priori conception of absolute space, which was rejected by (most) logical empiricists. 54 In a letter to Neurath, however, Carnap described the resolution as he met Kraus accidentally at Frank's house and Kraus admitted that their debate had cultural risk and talked it over. Carnap to Neurath, April 11-12, 1935 (RC 029-09-61). 55 Carnap to Schlick, March 5, 1933 (RC 029-28-31).
After 1933, given its general liberal atmosphere and its German-speaking university, Prague became somewhat of a center for German emigrants, and for many others from the Balkan and from the Soviet Union. Nevertheless, this paradise of diverging opinions and people was questioned already in 1934 when Carnap noted in his diaries that he asked Frank whether they should make a demonstration with the Prague biologist and philosopher of science Emanuel Rádl (1873Rádl ( -1942 and other professors against nationalism. While Frank agreed in principle, he thought that only a few people would join them. 56 The issue behind the demonstration was presumably the question of where to place the insignia of the university. After the university was divided into a German and a Czech University in 1882, they shared certain institutes, libraries, and, among others, the old insignia of 1338 that was kept in the German University. While Czech politicians required the insignia to be kept at the Czech University, their protests became more violent in the 1930s. On November 21, 1934 students of the German University had to hand over the regalia to the Czech part of the University. A few days later both German and Czech students became involved in the debate, the latter, outnumbering the German students, tried to attack the German University, while the Germans resisted. Finally, the regalia were given to Czech University, but nationalistic voices were strengthening from days to days on both sides, harming the relations between the nations and the universities. It was, however, the final straw. Carnap wanted to leave Prague even earlier: he aimed to find a Rockefeller fellowship, but it turned out in February 1934, that they did not have any philosophy position, and Carnap's project was not exactly mathematical. 57 The same thing happened as with his doctoral dissertation: he worked in a grey zone. A few months later, in August, when Charles Morris arrived to Prague, Carnap explained to him why he does not have any more chance in Middle-Europe. Morris could not promise anything regarding Chicago (he emphasized the Catholic tendencies of the department and that the chair wants Nicolai Hartmann), but he promised to look after Carnap's case. 58 Even before Morris could deliver any news, and right after Carnap found out that a lecture tour couldn't be arranged for him in New York (though Ernest Nagel tried to help him), he was invited to Harvard's 300 th -anniversary conference to hold a lecture and to take his honorary doctoral degree! "A first step towards America," he commented in the diaries. 59 A few months later, it turned out that Morris succeeded: Carnap was invited to the University of Chicago for the period January-March 1936. 60 On December 12, 1935, Carnap went to Dresden, then to Bremen in order to sail to the United States. As his representative and successor, Carnap suggested at first Neurath (he thought, however, that Neurath would not be the best candidate for a position at the Natural Science Faculty), then Walter Dubislav, Edgar Zilsel, Carl Hempel, and the German philosopher Ernst von Aster, who emigrated next year to Turkey; against Reichenbach both Frank and him had "personal misgivings" and Popper was not sympathetic to Frank. 61 As it is known, none of these figures got the job.
After Carnap went to the States, the situation did not get any better; actually it became worse on both sides of the ocean. In June 1936, Carnap wrote to Neurath that according to 56 Carnap's diary entry, November 30, 1934. 57 Carnap to Schlick, February 28, 1934 (RC 029-28-24). 58 Carnap's diary entry, August 17, 1934. The Thomist philosophers' resistance to logical empiricists is documented in Reisch 2005 and2017. 59 Carnap's diary entry, February 28. 1935. 60 Carnap's diary entry, August 5, 1935. On Carnap's invitation to Harvard, and how he transformed his own philosophy at the Harvard conference approaching the American audience, see Damböck (forthcoming). 61 Carnap's diary entry, November 25, 1935. On the context and relevance of possible nominating Neurath for the Prague-position (especially with regard to the history and internationalization of logical empiricism), see Tuboly (manuscript).
Frank, "anti-Semitism in Prague is again flourishing". 62 Carnap thus tried to help Frank, to come to the United States, but this did not work out effectively in the mid-1930s. Frank had to wait two more years in Europe, and he was able to visit America only in late 1938 and never moved back to the old continent. More interestingly, however, Carnap commented that by saying: "The world is hoggishly arranged. Over here anti-Semitism is vast as well, especially at the Universities,so for example, I heard that non-Aryans not even had the slightest chance to get the job at Princeton that I rejected." 63 Presumably, Carnap referred here to Reichenbach, who complaint to Louis Rougier that though Carnap recommended him for a Princeton job he was not able to take it because of an anti-Semitic trend there. 64 It is quite well known how hard was it for emigrants in general to adapt to the new life-conditions, but it is less known, how it was for others, like Edgar Zilsel (who committed suicide), Felix Kaufmann, Alfred Tarski, Karl Menger, or Carl Hempel etc. It is a story to be written: presumably an unsuccessful story like the one of the Prague Thursday Circle.