Ludwig Wittgenstein
Ludwig Wittgenstein; drawing by Siegfried Woldhek

The “Vienna Circle” was the self-chosen designation for a group of philosophers, scientists, and mathematicians, some three dozen in all, who came together in the mid-1920s with the ambition of purging philosophy of metaphysics and making it into the handmaiden of science. Every other Thursday evening, its members would convene in a dingy street-level lecture room at the University of Vienna to argue about how to do this. They took their inspiration from Albert Einstein, whose theory of relativity seemed to have transformed the conceptual basis of science, and from Bertrand Russell, from whom they absorbed the lesson that the essence of philosophy was logic. But the most potent influence on them was their relatively youthful contemporary Ludwig Wittgenstein, who—though he never deigned to join the circle or even attend one of its regular meetings—exerted a godlike and violently polarizing effect on its members.

The Vienna Circle organized itself with the fervor of a political movement, issuing manifestos, holding international congresses, and engaging in public outreach. Its members were united by their implacable hostility to traditional German idealism—including theology, which put them at odds with the clerical reactionary government that held power in Austria between the world wars. The circle’s scientifically rooted atheism and its rejection of religiously based ethics led to charges that it was corrupting the youth of Vienna. In 1936, its leader, Moritz Schlick, was shot to death by a deranged student on the steps of the University of Vienna’s main entrance. Two years later came the Anschluss. By that time most of its members had fled the city, the more prominent among them making their way to England and the United States.

This diaspora helped spread the philosophy of the Vienna Circle, which it called “logical positivism.” So did the publication in 1936 of Language, Truth and Logic, a lucid précis of the new philosophy by the then twenty-five-year-old A.J. Ayer, who had briefly attended meetings of the Vienna Circle during a honeymoon stay in the city. (It was Isaiah Berlin who prodded Ayer into writing the book, which proved to be enormously influential.) Over the next couple of decades, logical positivism became a main strand in the development of philosophy in the English-speaking world.

Today logical positivism has a whiff of the ridiculous about it. It conjures up a priggishly narrow-minded style of philosophy—scientistic, hair-splitting, at once arrogant and naive. Part of the problem is “positivism,” whose meaning has always been a bit elusive (rather like “hermeneutics”). The word was taken into English from the French positivisme, coined by Auguste Comte for his empiricist philosophy and his secular church of reason, l’église positiviste. In its primary sense, positivism connotes an emphasis on “positive” facts—i.e., observable ones—and their relations. But it has also been used, by George Eliot and other nineteenth-century writers, to mean “peremptoriness” or “certainty,” which are not attractive intellectual traits.

It was a pair of lesser members of the Vienna Circle who established the label in 1931 by publishing “Logical Positivism: A New Movement in European Philosophy” in the Journal of Philosophy. Before long it was being employed to refer not just to the ideas of the Vienna Circle, but more generally to the style of linguistic philosophy then being developed at Oxford and Cambridge—and often with pejorative intent. As Ayer observed in 1959, “This wider usage [of ‘logical positivism’] is especially favored by those who are hostile to the whole modern development of philosophy as an analytical rather than a speculative inquiry. They wish to tar all their adversaries with a single brush.”

One still occasionally hears “logical positivist” applied as a term of abuse to philosophers who show a retardataire adherence to strict empiricism. The intellectual project of the Vienna Circle—the drawing of a sharp distinction between meaningful discourse (mainly science) and “nonsense” (theology, metaphysics, ethics, poetry…)—has long been regarded as having expired from its internal contradictions. Even Ayer, its onetime evangelist, came to concede this, telling a BBC television interviewer in 1978 that the most important defect of logical positivism is that “nearly all of it was false.”

Did the influence of the Vienna Circle tend to impoverish philosophy, as some, like Thomas Nagel, have suggested? Or has logical positivism had an enduringly wholesome effect—mistaken perhaps in its specifics but, as Ayer continued to insist, “true in spirit”?

The answer is not to be found in Karl Sigmund’s oddly titled Exact Thinking in Demented Times, the first book-length portrait of the Vienna Circle to appear since the 1950s. Sigmund makes little effort to assess the legacy of logical positivism after the breakup of the circle. Nor does he furnish anything more than a superficial—and, in one respect, seriously inaccurate—survey of its philosophical antecedents. What he does supply is a brisk and engaging account of the volatile mix of characters that came together to form the Vienna Circle: their fierce intellectual battles over its main doctrines, their foibles and eccentricities, their “collective eroticism,” and their humiliations (mainly by Wittgenstein) and occasional mental breakdowns.


The book also gives a vivid picture of the “demented times” in which they attempted to carry out their “exact thinking,” chronicling how Vienna between the wars, diminished by the loss of its status as the capital of a multiethnic empire and riven by ideological tensions, descended from cultural vitality into Nazi barbarism. Sigmund, a professor of mathematics at the University of Vienna, has an intimate feel for his home city. And he has a sure command of science, as is apparent in his clear and charming explanations of the many technical ideas in which the Vienna Circle trafficked, from Einstein’s theory of relativity to Gödel’s incompleteness theorems.

All of this makes for a book that, if not philosophically sophisticated, is packed with information and, for the most part, a pleasure to read. But one thing detracts from its appeal: its pages are stuffed with hackneyed phrases. That may not be the author’s fault. The preface, by Douglas Hofstadter, tells the story of how the book, originally published in German as Sie nannten sich Der Wiener Kreis (They Called Themselves the Vienna Circle), came to be translated into English. Having read and enjoyed the book in German, Hofstadter emailed the author to say he would be honored to do the English translation. Sigmund wrote back to say that he had already translated it himself. Thereupon Hofstadter (who shares Sigmund’s American publisher) offered to put the “finishing touches” on the English-language version, and Sigmund accepted.

As those who have read Hofstadter’s best-selling book Gödel, Escher, Bach may recall, Hofstadter’s own prose can be strenuously playful, and he seems to have injected the same quality into the translation of Sigmund’s book. “As I carried out my editing task,” Hofstadter tells us in the preface,

I had the pleasure of inserting appropriate idiomatic phrases into the text here and there (such as “they weren’t a dime a dozen” and “he put physics on the back burner for a while”), and of throwing in quite a few other vivid turns of phrase.

The effect is to make the reader into an unwilling cliché-hunter. On a single page one comes across “smooth sailing,” “pleased as punch,” “highway robbery,” and “scarce as hens’ teeth.” Elsewhere horns are tooted, apples fall far from trees, a cold shoulder is received, wool is pulled over eyes, bloody murder is screamed, a pain occurs in a neck, and a tempest takes place in a teapot.

The founders of the Vienna Circle were not above resorting to hackneyed imagery themselves. In christening their group Der Wiener Kreis, they hoped to evoke images of Viennese waltzes and woods and, as one of them put it, “other things on the pleasant side of life.” But what was it that made Vienna the birthplace of logical positivism, the most radical revolt against the Hegelian-style metaphysics that had dominated European philosophy for a century? The University of Vienna was something of a philosophical backwater, having long been, as Sigmund puts it, “in the grip of the Jesuits.”

But the city also had a more recent tradition of scientifically based empiricism, one that was fortified in 1895 when a rich Viennese industrialist established a chair in the “History and Theory of Inductive Sciences” for Ernst Mach. A physicist by training (his name lives on in the expression “Mach one” for the speed of sound), Mach was a pioneering figure in the philosophy of science. His guiding conviction was that science was a logical structure erected on a foundation of experience. Anything not knowable through the senses, he held, was “metaphysical,” and hence unreal. Mach denied both the existence of atoms—which, since they could not be directly experienced, were mere theoretical fictions—and of the “I” or “ego,” which he dismissed as a bundle of sensations with no enduring unity.

Mach became a celebrated figure in the salons of fin-de-siècle Vienna, attracting the interest of Sigmund Freud, Arthur Schnitzler, and Hugo von Hofmannsthal. His doctrine that sense experiences, rather than material objects, were the proper stuff of science became so well known that Lenin wrote his Materialism and Empirio-Criticism to rebut it. Einstein credited Mach’s ideas with helping him see his way to relativity theory. The attitude of Mach’s admirers was summed up by the novelist Robert Musil, whose 1908 doctoral thesis, “Contribution to the Appreciation of the Teachings of Mach,” began, “The word of a scientist carries great weight…. The times are long gone when a picture of the world could emerge full-blown from a philosopher’s head.”


It was Mach, as Sigmund rightly stresses, who was in large part responsible for the emergence of logical positivism in Vienna. But he gives a misleading account of Mach’s intellectual lineage, and therefore of the lineage of the Vienna Circle. Both, he suggests, took their philosophical opponent to be Immanuel Kant. In the Critique of Pure Reason (1781), Kant had drawn a distinction between the phenomenal world—the world as we experience it—and the noumenal world of “things-in-themselves” that supposedly lies beyond all sensory experience. In Sigmund’s telling, it is this distinction that Mach was reacting against, since talk of a thing-in-itself seemed to lend an opening to the kind of metaphysics he despised. “Later on,” Sigmund writes, “a spirited opposition to Immanuel Kant would unite all the thinkers of the Vienna Circle.”

This is to misread their motivation. In fact, the logical positivists acknowledged that Kant, by arguing against the possibility of supersensible knowledge of the world, had made philosophy more scientific. Mach saluted Kant for having “banished into the realm of shadows the sham ideas of the old metaphysics.” And the Vienna Circle began as an avowedly neo-Kantian movement. It was from Kant that its members took the idea that knowledge has two distinct elements: a form and a content. The content comes from the world; the form is contributed by our minds.

Where the positivists came to differ from Kant was on the status of the formal elements of knowledge. For Kant, these elements were fixed and unrevisable, and this fixity was a source of a priori truths, like the truths of Euclidean geometry. But developments in mathematics and physics since Kant—non-Euclidean geometry in the nineteenth century, relativity in the early twentieth—seemed to have undermined the stability of the formal elements of knowledge. So the early positivists set about redrawing Kant’s form/content distinction.

It was Einstein who provided the greatest impetus to this shift. In framing relativity theory, he had employed a mathematical device, called the tensor calculus, that seemed to tease out the formal elements of our descriptions of nature and reveal their essential arbitrariness. And his most energetic interpreter—a man who became known as Einstein’s Hausphilosoph, or “pet philosopher”—was Moritz Schlick. Born in 1882 to a Berlin family in the minor aristocracy, Schlick earned a Ph.D. in physics under Max Planck (the originator of the quantum idea), then went on to publish a treatise on happiness titled Lebensweisheit (Wisdom of Life), stylistically modeled on Nietzsche. But it was his subsequent work on the philosophical implications of relativity theory that secured his renown. In 1922 Schlick accepted the offer of Mach’s old chair at the University of Vienna. His arrival in the city led to the beginning of the Vienna Circle—or the Schlick Circle, as it was initially called.

Besides Schlick, the most important founding member of the circle was Otto Neurath. A native of Vienna who had studied sociology and economics at the University of Berlin, Neurath contrasted sharply with Schlick. Whereas Schlick was elegant, decorous, and retiring, Neurath was a jocular, rumbustious fellow with a flowing mane of red hair, so tall and stout that he signed his letters by doodling the outline of an elephant. He was also—unlike Schlick and the rest of the Vienna Circle—a militantly political Marxist. After serving in the Austrian army in World War I, Neurath contrived to be put in charge of economic planning in Bavaria, remaining in the post even after the social democratic government in Munich was overthrown by a Spartacist coalition of communists and anarchists. When the Spartacists fell in a putsch by right-wing forces, Neurath was imprisoned, but the Austrian government intervened to have him released.

Neurath’s militancy extended into philosophy. He vociferously proclaimed the “unity of science”—by which he seemed to mean that the natural and social sciences should employ the same methods—and he detected signs of metaphysical backsliding even in fellow circle members like Schlick. Today Neurath is mainly remembered (when he is remembered at all) for his “ship metaphor,” meant to illustrate the provisional, antifoundationalist view of knowledge that he championed: “We are like sailors who have to rebuild their ship on the open sea, without ever being able to dismantle it in dry-dock and reconstruct it from the best components.”

A somewhat younger member of the Vienna Circle—and the one who became its most influential standard-bearer—was Rudolf Carnap. Like Schlick, Carnap was deeply impressed by Einstein’s ideas, writing a doctoral thesis titled Der Raum (Space). He also had a keen interest in logic as a tool for clarifying the concepts of science. As a student, he had attended the lectures of the great logician Gottlob Frege, in which he learned of Bertrand Russell and Alfred North Whitehead’s Principia Mathematica. Unable to afford a copy of the three-volume opus, Carnap wrote to Russell, who sent the unknown young German a thirty-five-page handwritten letter summarizing all its most important definitions and proofs.

Upon joining the circle in 1926, Carnap set a lofty standard for technical virtuosity. His main work during his time with the group was Der Logische Aufbau der Welt, translated into English as The Logical Structure of the World. In it he sought to demonstrate how, using the logic of Frege, Russell, and Whitehead, all of the concepts of modern science could be built up, step by step, out of a single solipsistic observer’s subjective experiences. (He later acknowledged that this project was a failure.) Carnap achieved wider notoriety for mocking Martin Heidegger’s pronouncement Das Nichts selbst nichtet (“The nothing itself nothings”) as a prime specimen of metaphysical claptrap. When he chanced to run into Heidegger at Davos while recovering from a lung ailment, he wrote to Schlick that he had encountered “a huge metaphysical cloud” that held within it…nothing.

Ferdinand Schmutzer/Austrian National Library/Anzenberger/Redux

Albert Einstein, Vienna, 1921

Carnap’s rigorous system-building helped give coherence to the Vienna Circle. But the stronger force of Wittgenstein’s personality threatened to tear it asunder. He had come to the circle’s attention early on. His Tractatus Logico-Philosophicus—written while Wittgenstein, who had volunteered for the Austrian army in World War I, was a POW in an Italian camp near Monte Cassino—was published in German in 1921, the year before its appearance in English. In its terse, numbered propositions, alternating between the technical and the sybiline, Wittgenstein had purported to solve all the problems of philosophy.

Schlick was enthralled, as were the other members of the Vienna Circle (with the exception of Neurath, who smelled metaphysics in Wittgenstein’s more oracular propositions). Over several semesters Schlick led the group through the Tractatus line by line, not once but twice. He became obsessed with meeting its mysterious author. By that time, Wittgenstein, the scion of a highly cultivated and enormously wealthy Viennese family, had renounced both his fortune and (temporarily) philosophy, and had become a schoolteacher in an impoverished Alpine village. When Schlick set out (in vain) to find him there, his wife commented: “It was as if he were preparing to go on holy pilgrimage, while he explained to me, almost with awesome reverence, that W. was one of the greatest geniuses on earth.”

The desired audience was finally obtained when Wittgenstein returned to Vienna to help design an austerely modernist house for his sister. (The architect with whom Wittgenstein worked on the project, Paul Engelmann, had previously collaborated with the journalist Karl Kraus and the architect Adolf Loos; he later quipped that he had been fortunate to learn “from the three best teachers of my generation: Kraus taught me not to write; Wittgenstein, not to speak; and Loos, not to build.”) Wittgenstein refused Schlick’s invitation to attend the circle’s regular Thursday-night sessions, but eventually he consented to meet with a few select members. The result was not what they had expected. Wittgenstein would sometimes simply sit with his back to them and read aloud the mystical poems of Rabindranath Tagore. Yet Schlick continued to venerate Wittgenstein, as did Carnap—despite his shock at discovering that Wittgenstein’s views, as he later put it, “were much more similar to those of a creative artist than to those of a scientist; one might almost say, similar to those of a religious prophet or a seer.”

Wittgenstein did not warm to the circle’s adoration. He found Carnap shallow, accused him of aping his ideas, and wrathfully cut off all contact when he discovered that Carnap had an interest in Esperanto—which Wittgenstein despised because it was not an organic language—and worse, parapsychology. He tortured another would-be acolyte, Friedrich Waismann, by repeatedly stymying his efforts to produce an accessible account of the Tractatus. “It is hell to work with me,” Wittgenstein complacently declared. Although he tolerated Schlick, whose cultivation he admired, he regarded the Vienna Circle as a “clique of busybodies” whose proud rejection of metaphysics amounted to “self-satisfied posturing.”

These personal frictions were symptomatic of something deeper. The Vienna Circle saw in Wittgenstein what it wanted to see, and this contributed to its undoing. Despite the circle’s early grounding in the ideas of Kant and Mach, Einstein and Russell, its leading tenets were arrived at by putting an empiricist spin on the Tractatus. For example, Wittgenstein had written that all propositions about the world could be analyzed into “elementary statements,” but he neglected to say just what form those elementary statements were supposed to take. The Vienna Circle, like good empiricists, took it for granted that elementary statements must be reports of observations—and proceeded to squabble inconclusively over whether they should be about private sensations (“red here now”) or publicly observable events (“a table was observed by Otto at 3:15 pm”).

The most distinctive doctrine of the Vienna Circle was the notorious “Verification Principle,” which equated the meaning of a sentence with its method of verification, and hence ostracized as meaningless all propositions that were not empirically testable—like “the real is rational,” or “beauty is significant form.” It too arose from a misconstrual of Wittgenstein, or so he was later to claim:

I used at one time to say that, in order to get clear how a certain sentence is used, it was a good idea to ask oneself the question: “How would one try to verify such an assertion?” But that’s just one way…of getting clear about the use of a word or sentence…. Some people have turned this suggestion about asking for the verification into a dogma—as if I’d been advancing a theory about meaning.

By the 1930s, in any case, Wittgenstein was moving away from the rigidly logical model of language set out in the Tractatus. Now installed as a professor at Cambridge, he began talking to his disciples of “language games” as a way of illustrating how linguistic meaning was rooted in rule-governed human practices in the stream of life. Meanwhile, the Vienna Circle was still engrossed in the futile task of finding a formulation of the Verification Principle that drew the boundary between sense and nonsense precisely where they thought it should be.

“Wittgenstein is a deity to them all,” Ayer wrote to Isaiah Berlin of the members of the Vienna Circle during his sojourn with them. But they failed to understand their deity, and then he left them behind. With the dissolution of the circle—already under way when Schlick was assassinated in 1936, and complete by the time the swastika was raised over Vienna two years later—the movement bifurcated. This was partly a matter of where its scattered adherents ended up. At Oxford—where Neurath and Waismann sought refuge, and where Ayer returned—and at Cambridge, logical positivism assimilated itself to the tradition of British empiricism, becoming a sort of language-parsing update of the philosophy of David Hume. In the United States, where several other members immigrated—notably Carnap, who moved first to the University of Chicago and then to UCLA, and Carl Hempel, who took a position at Princeton—its more technical side came to the fore. Work done in a positivist vein, especially bearing on the methodology of science, did much to shape the development of American philosophy in the postwar era.

By the late 1950s, however, the influence of logical positivism had begun to wane. A decade later the movement was dead, both in England and the United States. Its demise is sometimes traced to a single essay that appeared in 1951: the brief but astonishingly potent “Two Dogmas of Empiricism,” by the American philosopher Willard Van Orman Quine. The two dogmas in question—first, that a sharp distinction can be drawn between “analytic” statements that are true by definition and “synthetic” statements that depend on how the world is; second, that every meaningful statement corresponds to a set of experiences that would validate it—were both dear to logical positivists. Both were demolished by Quine’s arguments, or so it widely came to be believed.

After the death of Wittgenstein that same year, it was Quine who took his place as the living philosopher who, in the words of Ayer, “commanded the greatest influence among his colleagues, at least in the English-speaking world.” He pretty much held that place until his death in 2000. As it happens, Quine, back when he was a freshly minted Harvard Ph.D. in the 1930s, had done a stint as a visiting member of the Vienna Circle, then in its heyday. (Unlike Ayer, the other junior member from abroad, the linguistically gifted Quine was fluent in German.) Although he later attacked its principal tenets, he stayed true, for better or worse, to the circle’s core conviction: that philosophy must be continuous with science. Therein lies the ironic legacy of the Vienna Circle: that Quine, who did more than anyone to usher it off the stage, should himself come to be regarded as—to quote his Harvard colleague Hilary Putnam—“the greatest logical positivist.”