After the First World War, the members of the Vienna Circle tried to put European thought on a rigorously logical footing. Then the times caught up with them.

Vienna circle
Influenced by Wittgenstein, the Vienna Circle aimed to make language logical.Illustration by Yann Kebbi

Philosophy often flourishes in the aftermath of wars, especially lost wars. Socrates served in the losing Athenian army in the Peloponnesian War; Thomas Hobbes wrote “Leviathan” while in exile in Paris after the defeat of the royalists in the English Civil War. At moments of humiliation and confusion, when people need to rebuild their understanding of the world, they are willing to rethink assumptions that go unchallenged in normal times.

The defeat of the Central Powers in the First World War gave rise to one of these historic bursts of creative thinking. Ludwig Wittgenstein, perhaps the most influential philosopher of the twentieth century, served in the war as an artillery officer in the Austro-Hungarian Army. Captured just days before the Armistice, in November, 1918, he spent nine months as a prisoner of war in Italy before returning home to Vienna, an imperial capital suddenly stranded in a small, parochial new state.

It was while on leave in the summer of 1918 that Wittgenstein completed his “Tractatus Logico-Philosophicus,” which was published in 1921. Today, it is Wittgenstein’s later work that commands the most attention, but the “Tractatus”—a brief, dense book that, like Euclid’s treatise on geometry, takes the form of a series of numbered propositions—magnetized readers from the start with its radical ambition. It aimed to tear Western philosophy up by the roots, just as revolutionaries on the left and the right were doing to societies all across postwar Europe.

For Wittgenstein, the renovation of philosophy had to begin with language. Since the Greeks, Western thinkers had tried to understand the world using terms such as “being” and “becoming,” “substance” and “essence,” “real” and “ideal.” But these abstractions gave rise to complicated arguments that went around and around, never reaching any definite conclusion. Now, in the early twentieth century, relativity and quantum theory were redrawing the map of reality in ways that could be verified by experiment and given precise mathematical expression. In an age of triumphant physics, did philosophy still need to bother with metaphysics?

By declaring the answer to be no, Wittgenstein set modern thought on a new course. For the analytic philosophy he helped inspire, many of the discipline’s traditional problems are actually just misunderstandings, based on an erroneous use of language. What philosophers need isn’t profundity but clarity: as Wittgenstein says in the “Tractatus,” “Everything that can be thought at all can be thought clearly. Everything that can be said can be said clearly.”

This way of thinking about language—what it means, what it can grasp, and how it should be used—became the particular obsession of the Vienna Circle, a group of scientists, mathematicians, and philosophers who met regularly from the mid-nineteen-twenties to the mid-thirties, mainly at the Mathematics Institute of the University of Vienna. The best known of its dozen or so core members are the logician Rudolf Carnap, the sociologist Otto Neurath, the mathematician Kurt Gödel, and Moritz Schlick, who turned to philosophy after earning a doctorate in physics under Max Planck, the pioneer of quantum theory. These thinkers and their students helped set the agenda for postwar academic philosophy in Britain and America, where most of the Circle’s members ended up teaching after they fled the Continent in the thirties.

Taking its cue from the “Tractatus,” the Vienna Circle sought to make language as precise and rigorous as a mathematical proof. The English philosopher A. J. Ayer, who studied in Vienna and helped popularize the Circle’s ideas, summed up its definition of the purpose of philosophy: “to dispel those confusions which arise from our imperfect understanding of certain types of sentence in our language.” If this “linguistic turn,” as it came to be known, sounded uninspiring or even priggish, so much the better; philosophy had been led astray for too long by grand, seductive illusions.

David Edmonds’s new book, “The Murder of Professor Schlick” (Princeton), offers a lively and accessible introduction to this much written-about group. Rather than plumbing the depths of the Vienna Circle’s work, which is formidably technical, Edmonds mainly explores how its ideas reflected the group’s tumultuous time and place. His research has also uncovered important new biographical information, including about its lesser-known female members.

Wittgenstein never attended a meeting of the Vienna Circle, but he knew its key figures, and his ideas dominated its proceedings. In Edmonds’s book, too, Wittgenstein ends up stealing the focus, simply because he played the role of genius so perfectly—intense and charismatic, unworldly and unpredictable, shockingly arrogant yet capable of remarkable self-sacrifice. It didn’t hurt that he was also handsome and rich, having been born into one of Austria-Hungary’s leading industrial dynasties.

In 1919, however, Wittgenstein gave up his share of the family fortune. He spent the next seven years teaching elementary school in remote Austrian villages, where he made himself loathed by regularly beating his pupils and pulling their hair. In 1926, after he returned to the capital, he made contact with the Vienna Circle, whose members had been studying the “Tractatus.” The wife of Schlick, the group’s leader, recalled that the first time her husband dined with Wittgenstein he returned “in an ecstatic state.” Another philosopher, Friedrich Waismann, “began, subconsciously, to imitate Wittgenstein’s speaking patterns.”

Edmonds’s subtitle, “The Rise and Fall of the Vienna Circle,” suggests a closer connection between the group’s work and the titular murder than the book actually establishes. Schlick’s death had nothing to do with his ideas; he was killed by a psychotic former student, Johann Nelböck, who had been stalking and threatening him for years and finally shot him, in June, 1936, on the steps of a university building. But what happened next, Edmonds shows, was indeed shaped by what the Vienna Circle had come to represent in the ideological frenzy of interwar Austria.

No sooner had news of the crime broken than the nationalist, anti-Semitic press began to extenuate and even to praise it as a blow against degenerate Jewish thought. Schlick was accused of damaging “the fine porcelain of the national character” and of embodying Jewish “logicality, mathematicality, [and] formalism,” qualities inimical to “a Christian German state.” One writer urged that the murder should “quicken efforts to find a truly satisfactory solution of the Jewish Question.” Nelböck, at his trial, played to this sentiment, claiming that he had killed Schlick for ideological reasons. That defense didn’t keep him out of jail, but after Nazi Germany annexed Austria, in 1938, Nelböck was released, on the ground that his crime had been inspired by “strong national motives and explicit anti-Semitism.”

In this deranged atmosphere, no one was deterred by the fact that Schlick was not Jewish but, rather, a German Protestant. Some of his defamers probably didn’t know this, but others simply didn’t care, since in their eyes Jewishness wasn’t defined only by religion or ethnicity. It was also a mind-set, characterized by the modernism and liberalism they saw as sources of spiritual corruption.

In this sense, Nazis and Austria’s Christian fascists were right to see the Vienna Circle as an enemy. In Edmonds’s words, the Circle was “contemptuous of superstitious thinking,” including myths about race and religion. The group included Christians and Jews, but its members’ real creed was what they called “the scientific conception of the world.”

That was the title of a 1929 manifesto in which the Circle announced its intellectual program. Written as a tribute to Schlick, who was returning to Vienna after a stint at Stanford University, the essay explained that the members of the Circle, though they didn’t agree on everything, were committed to two basic principles. First, “there is knowledge only from experience, which rests on what is immediately given. This sets the limits for the content of legitimate science.” Second, “the scientific world-conception is marked by application of a certain method, namely logical analysis.”

Together, these ideas gave the new school of thought its name, logical empiricism. For logical empiricists, philosophy doesn’t deal with ideas or things; it deals with statements, sentences, propositions. By putting together a series of true statements, it’s possible to create what Wittgenstein, in the “Tractatus,” called a “model of reality,” a representation of the world in language. The content of statements about the world is determined by experience, including the refined and controlled type of experience that comes from scientific experiment.

Philosophy’s role in the search for truth is to examine the form of our statements, to insure that they are syntactically and logically correct. To this end, the Vienna Circle drew on the symbolic logic developed by the English philosopher Bertrand Russell, which offered a way to reduce any sentence to a series of symbols and formulas. Many pages of Carnap’s 1934 book, “The Logical Syntax of Language,” look as if they could have come from a math textbook.

Symbolic logic is useful because statements can go wrong in ways that ordinary usage makes it hard to detect. In most cases, determining whether a statement is empirically true or false is fairly straightforward. If someone says that the moon is made of green cheese, there are various ways to check: you could look at the moon through a telescope, or examine a moon rock, or calculate how a moon-size ball of green cheese would behave in outer space. Even if false, “The moon is made of green cheese” is still a meaningful proposition, because it makes an assertion about the world that can be tested.

Some statements, however, can’t be proved true or false, because they are constructed in a way that violates the rules of language. Carnap labelled these “pseudo-statements”—“a sequence of words [that] looks like a statement at first glance,” but whose syntax or vocabulary renders it meaningless. He gave as an example “Caesar is and”: if someone said this to you, you wouldn’t say that she was right or wrong, just that she didn’t know English syntax.

For the Vienna Circle, the best hunting ground for pseudo-statements was metaphysics, the branch of philosophy that deals with fundamental concepts like being and essence, time and space. Since Aristotle, who called it “first philosophy,” metaphysics had been seen as the highest and most disinterested form of thought. For Immanuel Kant, it was “the queen of all the sciences.” But, for the members of the Vienna Circle, metaphysics was a queen like Marie Antoinette—imperious, out of touch, and ripe for the guillotine.

The problem with metaphysical statements is that they are generally unverifiable, which to the logical empiricists meant they are meaningless. In Carnap’s 1932 essay “The Elimination of Metaphysics Through Logical Analysis of Language,” he asks us to imagine a man who invents a new adjective, “teavy,” and who, when we ask him how to tell whether or not something is teavy, replies that “there are no empirical signs of teavyness.” In that case, Carnap says, “we would deny the legitimacy of using this word.”

The same principle, he argues, should apply to metaphysical terms, from Plato’s “Idea” to Kant’s “thing-in-itself.” Such impressive words may provoke “associated images and feelings,” Carnap writes, but they have no actual meaning, so any explanation that relies on them is saying nothing at all.

Metaphysics wasn’t just a ghost from the past to be exorcised; it was still on the march, with important consequences for both philosophy and politics. Carnap’s essay was written as an attack on Martin Heidegger, the other great German-language philosopher to emerge after the First World War. If Wittgenstein’s “Tractatus” is a fundamental work of analytic philosophy, Heidegger’s 1927 book, “Being and Time,” is equally important for “Continental” philosophy—a catchall term used by the Anglo-American analytic school to refer to all those benighted Europeans who still take metaphysics seriously.

Heidegger and Wittgenstein shared an ability to inspire awe and devotion, but in most respects the two were opposites. Wittgenstein was raised in privilege in Vienna; Heidegger grew up poor in Messkirch, a small town in rural Germany, where his father was the sexton of the Catholic church. Wittgenstein was a wanderer who moved back and forth between Austria and England, and between academia and other pursuits; Heidegger spent his entire career at the German university where he had been a student, and did his thinking in a remote cabin he built in the Black Forest. (That cabin, the most famous dwelling in twentieth-century philosophy, is the subject of its own book, “Heidegger’s Hut,” by Adam Sharr.)

Above all, the two men differed in their opinion of the value of metaphysics. In 1929, the year that the Vienna Circle published its manifesto, Heidegger delivered a lecture whose title, “What Is Metaphysics?,” was a red rag waved in the face of the logical empiricists. Indeed, he began by acknowledging that modern science has no use for metaphysics. According to the scientific conception of the world, only things we can experience directly are real; the domain of knowledge is “beings themselves—and nothing besides.”

The second part of that statement, he argues, far from being a throwaway phrase, reveals a fundamental truth: in addition to beings, there is the nothing. We come to understand the nothing not through reason but through the experience of anxiety; in moments of existential angst, “beings as a whole slip away, so that just the nothing crowds round.” It is only because we encounter the nothing in this primal way that we are able to understand logical concepts like negation and nonexistence. As Heidegger puts it, “das Nichts selbst nichtet”—a strange phrase that English translators have rendered as “the nothing itself nihilates,” or even “the nothing itself noths.”

For Heidegger’s many admirers, his dislocation of language gave metaphysical concepts back the power and strangeness they had lost over the millennia. The way he roots philosophy in mood, rather than in mere intellection, makes his work imaginatively engaging in ways that logical empiricism can’t achieve. One might say that Heidegger wanted to make philosophy more like poetry, whereas the Vienna Circle wanted it to be more like math. For Carnap, the poetic dimension of Heidegger’s thought was precisely the issue, since it depended on misusing language to create an illusion of profundity. The problem, he writes in “The Elimination of Metaphysics,” is grammatical: because German (like English) treats the word “nothing” as a noun, it can be used as the subject of a sentence. For instance, if someone asks, “What is outside?,” you might reply, “Nothing is outside,” just as you could say, “Rain is outside.” This creates the illusion that “nothing” is an entity like rain, whose properties and actions can be described. Syntactically, “The nothing reveals itself” seems to be the same kind of statement as “The rain falls down.”

This is exactly the kind of error we need logic to rescue us from. When we say “Nothing is outside,” Carnap argues, we’re using a kind of verbal shorthand; what we really mean is “There does not exist anything which is outside.” Phrasing it this way shows that the word “not” can properly be used only to negate a proposition. Using it as the subject of a proposition, as Heidegger does, is at best a sign of mental confusion, and at worst a deliberate attempt to mystify and mislead.

Indeed, in “What Is Metaphysics?,” Heidegger explicitly says that he wants to get rid of logical thinking, so that “the very idea of ‘logic’ dissolves in the whirl of a more basic questioning.” This was the fundamental disagreement that separated Heidegger from the Vienna Circle: he believed that language could discover truths deeper than logic; the Circle believed that language without logic could yield only nonsense. As Wittgenstein warned in the last sentence of the “Tractatus,” “Whereof one cannot speak, thereof one must be silent.”

Whereof the Vienna Circle could speak, however, it had a lot to say. Its 1929 manifesto gave rise to a new journal, a series of conferences to bring together leaders in various scientific fields, and an International Encyclopedia of Unified Science, which aimed to summarize all of scientific knowledge in two hundred volumes. Still more broadly, the manifesto announced that logical empiricism entailed a particular approach to “questions of life”: “Endeavors toward a new organization of economic and social relations, toward the unification of mankind, toward a reform of school and education, all show an inner link with the scientific world-conception; it appears that these endeavors are welcomed and regarded with sympathy by the members of the Circle, some of whom indeed actively further them.”

That was certainly true of Otto Neurath, one of the main authors of the manifesto and the most vivid personality in the Circle. Neurath, a committed leftist who had participated in the failed revolution in Munich in 1919, was an adept publicist of ideas. He was the one who named the group, hoping, in the words of a fellow member, Philipp Frank, to evoke “other things on the pleasant side of life,” such as Viennese waltzes. When he wasn’t philosophizing, Neurath worked on public housing, adult-education programs, and a new method of representing data in easily comprehensible pictograms, known as Isotype, which resulted in the visual vocabulary now used in infographics throughout the world.

But not everyone in the Circle was happy to be dragged into political debates—including Schlick, whom the manifesto was intended to honor. Edmonds brings to life the volatile political and cultural scene in nineteen-twenties Austria, a small country created after the First World War out of the German-speaking lands of the former Habsburg Empire. Vienna, a city of two million people, had been the right size for the capital of a far-flung multinational state, but now it found itself in a country of just 6.5 million people.

“Red Vienna,” as it was nicknamed, had a socialist government, a cosmopolitan culture, and a large Jewish population. All three aspects made it thoroughly hated by the rest of the country, which was rural, conservative, and Catholic. Austria came to the brink of civil war in the twenties, and in 1933 it became a fascist dictatorship under the rule of the Fatherland Front. In these circumstances, the Vienna Circle had much to lose from becoming publicly identified with the left.

In 1934, the group came under scrutiny from the police, prompting Schlick to write letters to state agencies insisting that it was “absolutely unpolitical.” The letters didn’t help; the Circle’s official sponsoring organization was dissolved, and some members were forced out of their jobs or arrested. Though the annexation of Austria by Nazi Germany was still four years away, the members of the Circle began to look for opportunities to emigrate.

Many ended up in America, where they helped shape the next generation of academic philosophers. Herbert Feigl went to the University of Iowa in 1931; Carnap was hired by the University of Chicago in 1936. Kurt Gödel, famous for his “incompleteness theorem” and his complete unworldliness, didn’t wake up to the danger until the Second World War began. After receiving a job offer from the Institute for Advanced Study, in Princeton, in January, 1940, he had to go the long way around, crossing the entire Soviet Union, the Pacific Ocean, and the United States to get to New Jersey.

For the lesser-known members of the group, things were tougher. Edmonds documents the struggles of Rose Rand, a Jewish woman who earned her doctorate from the University of Vienna in 1938 but couldn’t find a secure academic job in England, forcing her to rely on the grudging charity of émigré organizations. Wittgenstein intervened on her behalf, but even he found her demanding and difficult to deal with. Still, she survived, living and teaching until 1980. Remarkably, no one from the Circle was killed by the Nazis.

Meanwhile, as the logical empiricists fled for their lives, Heidegger was on the rise. After Hitler’s takeover in Germany, in 1933, the philosopher was appointed rector of the University of Freiburg and given the responsibility of bringing it into alignment with Nazism. An enthusiastic Nazi, Heidegger saw his task in metaphysical terms, declaring in his inaugural address that the essence of science is “the questioning standing of one’s ground in the midst of the constantly self-concealing totality of what is.” Carnap would have scoffed at this language; but as the Vienna Circle knew, and Germany and the world were about to find out, pseudo-statements can have very real consequences. ♦

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