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https://en.wikipedia.org/wiki/Otto_Neurath
https://plato.stanford.edu/entries/neurath/index.html
"Neurath was a social scientist and activist, scientific philosopher and maverick leader of the Vienna Circle who championed the so-called scientific attitude and the Unity of Science movement. He denied any value to philosophy over and above the pursuit of work on science, within science and for science and society. And scientific results, he argued, are not logically fixed, securely founded on experience or can be ordered in a System of knowledge. Uncertainty, decision and cooperation are intrinsic to scientific practice. From this naturalistic, holistic and pragmatist viewpoint, philosophy investigates the conditions of the possibility of science as apparent in science itself, namely, in terms of physical, biological, sociological, historical, psychological, linguistic, logical or mathematical conditions. His views on the language, method and unity of science were led throughout by his interest in the social life of individuals and their well-being. To theorize about society is inseparable from theorizing for and within society. Science is in every sense a social and historical enterprise and helps society understand the past, explore possibilities and engineer the future. It is as much about social objectives as it is about physical objects, and about social realizations as much as about empirical reality. Objectivity and rationality, epistemic values to constrain scientific thought, were radically social. His contributions to visual education –based on pictorial languages–, museology, urban planning, and political economy –especially on collective welfare, ecological economics and the unavoidability of multi-criterial evaluation– constitute concrete legacies that have regained relevance, interest and urgency.
Otto Neurath was born on 10 December 1882 in Vienna. He was the son of Gertrud Kaempffert and Wilhelm Neurath, a Hungarian Jewish political economist and social reformer. While benefitting from his father’s vast polymathic library, in Vienna he studied literature, mathematics, physics, history, philosophy and economics (although he formally enrolled at the University of Vienna only for two semesters in 1902–3). Next he followed the social scientist Ferdinand Tönnies’s advice to move to Berlin, where he received a doctoral degree in history of economics in 1906. He studied under leaders of the so-called Young German Historical School Eduard Meyer and Gustav Schmoller and he was awarded the degree for two studies of economic history of antiquity, one on Cicero’s De Officiis and the other with an emphasis on the non-monetary economy of Egypt.
On his return to Vienna, he joined other economists such as Joseph Schumpeter and Ludwig von Mises at postdoctoral seminars led by theoriests of Carl Menger’s so-called Austrian School Eugen von Böhm-Bawerk and Friedrich von Wieser. At the time Neurath engaged ongoing debates over the unity of the sciences –especially the distinction between Naturwissenschaften and Geisteswisshenschaften–, the role of values in science and goals and methods of economics (Uebel 2004). The debates would prompt early views on the practice of science and inform his subsequent positions within scientific philosophy and logical empiricism.
His first publications were in the history of political economy and logic, a subject he had formally learned at the University of Vienna. In the history of political economy, topics included the history of money and economic organizations in antiquity, and his publications included textbooks and readers either co-authored or co-edited with his first wife Anna Schapire-Neurath, expert in literature and social issues. The papers on logic focused on issues in algebraic logic and included one paper, of 1909, co-authored with his friend and second wife, Olga Hahn, a sister of the mathematician Hans Hahn (she shortly after received a doctorate for her logic work). Neurath’s subsequent theorizing on the social sciences and his contributions to debates on logical empiricism integrated both disciplines. With the mathematician Hans Hahn and the physicist Philip Frank, around 1910 Neurath formed in Vienna a philosophical discussion group focused on foundational crises in physics and mathematics and the philosophical ideas about science of Vienna’s positivist Ernst Mach and the French conventionalists Pierre Duhem, Abel Rey and Henri Poincaré. A great deal of philosophical and scientific concerns and insight were already in place in Neurath’s thinking and projects. With a grant from the Carnegie Endowment for International Peace, a subsequent study of the Balkan Wars and then World War I led him to develop a theory of war economy as a natural (non-monetary) economy, or economy in kind, and to propose models for its peacetime implementation as a solution to endemic socio-economic problems of capitalism.
In 1919 the short-lived Bavarian socialist government (November 1918-April 1919) appointed him head of the Central Planning Office. The fall of the subsequent Bavarian Soviet Republic in May 1919 got him expelled from his junior post teaching economic theory under Max Weber at Heidelberg University, where he had received his Habilitation in 1917. His program for full socialization of the economy was inspired by his studies of war economics and based on his theory of natural economy and a holistic requirement to bring different institutions and kinds of knowledge together in order to understand, predict and control the complex phenomena of the social world (see the supplementary material on Political Economy). His driving social concern was collective welfare or happiness, which he came to consider not a form of utiltarianisn but of Epicurean socialism.
From 1921 until 1934 Neurath participated actively in the development of socialist politics, especially in housing and adult education, in so-called Red Vienna (on his political life, see Sandner 2014). He established the Social and Economic Museum of Vienna, where he developed and applied the ‘Vienna method’ of picture statistics and the ISOTYPE language (International System of Typographic Picture Education) (see the supplementary document on Visual Education). Like the thought of other Viennese philosophers such as Ludwig Wittgenstein and Karl Popper, Neurath’s philosophy was inextricably linked to pedagogy, logic, critique of language and, in Popper’s case, political thought. In 1928, with members of the Austrian Freethinkers Association and the Vienna City Council and the scientifically-trained members of the informal circle around the current holder of Mach’s University Chair, the philosopher Moritz Schlick (1924–29), Neurath helped found the Verein Ernst Mach, the Ernst Mach Association for the Promotion of Science Education. The publication in 1929 of an intellectual manifesto gave way to the formation of the Vienna Circle, whose narrower goal was the articulation and promotion of a scientific world-conception and logical empiricism (on the Viennese intellectual landscape, see Stadler 2001).
When in 1934 the Austrian government allied itself with the German Nazi government, Neurath fled to the Netherlands. As a result, his local, Viennese, socialist Enlightenment project turned into an internationalist, intellectual and social-political project. He created the International Foundation for Visual Education in The Hague, with his assistants from Vienna, and spearheaded the International Unity of Science movement. The latter, inspired by a tradition culminating in the Enlightenment’s French Encyclopedists, launched the project of an Encyclopedia of Unified Science. Together with the pictorial languages, the scientific encyclopedia would promote scientific and social cooperation and progress at an international level. After Austria became part of the German Reich in 1938, even though living in the Netherlands, Neurath was considered a German citizen and a ‘half-Jew’ and he was not allowed to marry his ‘Aryan’ assistant Marie Reidemeister—after his second wife, Olga, had died in 1937. During this period, he travelled abroad, including the United States, where logical empiricism had become entangled with the Cold War political and intellectual debates and witch hunts (on the Cold War phase, see Reich 2005). Carnap and Charles Morris at the University of Chicago acted as his co-editors of the International Encyclopedia of Unified Science. New York leftist intellectuals hosted him as an intellectual and political ally. And his maternal first cousin Waldemar Kaempffert, influential editor for The New York Times and Popular Science, introduced him as an international reformer and visionary, praising his science-oriented intellectual, social and educational ideas, especially his contribution to unity of science and visual language (see Reisch 2019). After the Nazi invasion of the Netherlands in 1940, Otto Neurath and Marie Reidemeister fled to England, on the small Seaman’s Hope. After nine months in an internment camp they resumed activities related to the Isotype language, public education and the unity of science. He died in Oxford on 22 December 1945 (on activities in the camp see Henning 2019; on activities after see Körber 2019 and Tuboly 2019).
by 1910 Neurath had already been involved in debates on the issues of scientific unity and methodology. They were prompted by his research in economics as well as foundational issues in mathematics and physics and reading in positivism and conventionalism. His early metascientific, or philosophical, views developed along with his economic thinking and evolving historical context. In projects of socialized, planned economic reform and in his broader notion of economics, they featured interrelated concepts and concerns: unity, rationality, precision, possibility, planning, decision, control, construction –or engineering–, communication, coordination, history and their social dimensions and applications. The same issues –alongside illustrating references to boats and Robinson Crusoe– would later play a defining role in his epistemological and methodological contributions to logical empiricism (Nemeth 1991, Cat et al. 1991 and 1996 and Cat 2024).
For instance: (1) a notion of theorizing in natural and social sciences, including history, based on the historical exploration of combinatorial possibilities and models, past and future; (2) the application in the social sciences of empirical goals and methods of the natural sciences; (3) a unifying public (objective and testable) language for scientific data and hypotheses, with a private-language argument anticipating Wittgenstein’s own and also illustrated by the case of Robinson Crusoe; (4) the evaluation and choice of data and hypotheses characterized by a logical under-determination of hypotheses by data and the conventional and pragmatic aspect of rational decision-making and control (with a role for so-called auxiliary motives); (5) the historical, social, cooperative, planned and constructive (engineering) dimensions of scientific research (a ‘republic of scientists’); (6), connectedly, a holistic approach to scientific knowledge and its application in the form of encyclopedic unification without hierarchical systems as a tool for successful prediction and engineering of events in a complex world –an ‘encyclopedia model’, by establishing cross-connections among disciplines, as in a Crusonian archipelago: a ‘great, rather badly coordinated mass of statements’ in which at best ‘systems develop like little islands, which we must try to enlarge’ (Neurath 1936/1983, 153)–; and (7) the social relevance of scientific philosophy, especially the unification and demarcation of science against metaphysics.
Regarding unification, Neurath endorsed a broader notion of economics based on symbolic (or logical) rather than merely quantitative precision and a historical perspective that included the use of empirical methods and theoretical distinctions common in the natural sciences; the combination served the purpose of comparing and classifying past cases and future possibilities (Neurath 1910). In addition, Neurath’s proposal of a moneyless war economy sought to maximize human happiness rather than private profit, and was based on a set of incommensurable indicators rather than the uniform monetary measurement unit. An economic plan for a socialized economy required the consideration of the different indicators that in turn required a holistic organization of information and individuals to coordinate decisions and action (rather than a market). Prediction and action required different forms of unity.
This engineering value of unity applied equally to political governance and scientific action, since both are collective and pragmatic endeavors. According to Neurath, ‘scientific theories are sociological events’ (Neurath 1932a/1983, 88), and, since ‘our thinking is a tool’, in this case the ‘modern scientific world-conception’ aims to ‘create a unified science that can successfully serve all transforming activity’ (Neurath 1930/1983, 42). In both cases, Neurath noted, ‘common planned action is possible only if the participants make common predictions’ and group predictions yield more reliable results; therefore, he concluded, ‘common action presses us toward unified science’ (Neurath 1931/1973, 407). Indeed, all along, for Neurath scientific attitude and solidarity (and socialism) go together (Neurath 1928/1973, 252).
Economic planning was a matter of consideration of possibilities and making rational decisions. But for Neurath, practical and theoretical rationality was not a matter of mechanical, objective calculation or reasoning alone –especially in the absence of full insight and a uniform quantitative monetary unit. In a study of psychology of decisions he dismissed such a standard of rationality as “pseudo-rationalism” (Neurath 1913). Planning was a pragmatic (social) engineering problem, namely, a matter of construction and control, and decisions among alternative possibilities that required judgement, external goals or just a coin flip –auxiliary motives (Neurath 1913). Both rationality and the irreducibly social perspective were matters of debate among economists, including Karl Marx, and illustrated, also by Neurath, with references to the fictional figure of Robinson Crusoe stranded on an island.
Along similar lines, we can place Neurath’s contributions to the Vienna Circle’s project of a scientific world-conception and logical empiricism in context of his evolving political epistemology. Considerations of knowledge at the theoretical or practical service of politics played a central role in his work on economic planning. He envisioned the role of rationality and the coordination of information and political goals mentioned above also in relation to socialist democratic model of participation of citizen workers. Deliberation and decision making required communication, also of social and economic information. For such education purpose, at the service of participation, Neurath designed a pictorial language (Sandner 2014, Groß 2019 and Nemeth 2019; see also supplementary material on visual education). This discursive approach to communication of knowledge and decision making was also part of his objection and alternative to models such as Hayek’s based on the role of markets and prices (Hayek 1935, Neurath 1942). Neurath’s economic planning was neither technocratic nor dictatorial (Chaloupek 2008). But it relied on expert proposals.
In exile in the 1940s the socialist internationalism of his social models turned more liberal, combining international planning for freedom and liberal democracy. Neurath addressed the role of experts and the distinction between esoteric and exoteric, or lay, knowledge and promoted the democratization of knowledge: ‘what we call democracy implies a rejection of experts in making decision[s]’ (Neurath 1996, 251). But how much democratization required or could achieve in such checks on expert power has been debated (Wussow 2021).
Neurath formulated his empiricist epistemology through the 1930s in similar terms of checks and controls. Data statements he called control statements; and the dynamics of knowledge formation and revision was a matter of formal and empirical controls. Relative to the resulting unity in a theory or body of knowledge, metaphysical statements could be identified and rejected as uncontrolled and isolated
3.1 Language
Neurath’s later views on the language and method of science expressed his simultaneous response to earlier problems in the social sciences and to philosophical issues addressed by the Vienna Circle between 1928 and 1934. A primary aim of the Vienna Circle was to account for the objectivity and intelligibility of scientific method and concepts and to demarcate scientific from metaphysical statements. Their philosophical approach was to adopt what the Circle member Gustav Bergmann called the linguistic turn, namely, to investigate the formal or structural, logical and linguistic framework of scientific knowledge. Within this framework members of the Circle pursued the aims of intelligibility and demarcation by means of two connected conditions of meaning and meaningfulness. The former –stronger– often was formulated mainly by Moritz Schlick (after Wittgenstein) as a condition of empirical verification. The latter –weaker– was a related semantic condition of empirical verifiability, formulated mainly by Rudolf Carnap in different ways over time, and was supplemented by a syntactic condition of formal or grammatical correctness (Uebel 2007). The formal approach encompassed logicism and logical analysis as views about the formation, interpretation, justification and acceptance especially of theoretical statements. The problem of empiricism became then the problem of coordination between the formal theoretical structures and the records of observations in such a way that it also offered an explication of how scientific knowledge can and should be formally constructed (especially in logic and mathematics), empirically grounded (except logic and mathematics), and thereby understood, evaluated and accepted.
Sources of Neurath’s attention to language are multiple. Besides Neurath’s own early interest in logic and classical and ancient languages, the value of attention to language was familiar to Neurath from the Austrian fin-de-siècle culture of critique of language (Janik and Toulmin 1973), his interest (and his first wife’s) in literature, especially in Goethe (Zemplen 2006), Marx and Engels’ attention to the radically social dimension of language (and its relation to money), the internationalist and utopianists efforts at introducing new universal languages such as Volapük and Esperanto, the emphasis on signs and universal languages – to be known as pasigraphy – in the scholastic and rationalist philosophical traditions, in the traditions of empirical taxonomies and in the interest in universal language as instrument of knowledge and social order in the Enlightenment, a semiotic tradition in scientific epistemology including Helmholtz, Mach, Duhem and Peirce (Cat 2019) and the sociologist Ferdinand Tönnies’s formal approach to sociology and social signs (Tönnies 1899–1900 and Cartwright et al. 1996). The significance of the internationalist and philosophical projects of so-called pasigraphy were acknowledged also by Carnap. More “scientific” sources were recent technical developments in logic, philosophy of science and the foundation of mathematics often claiming Leibniz as a precursor (Leibniz’s logic and project of a universal characteristic had become widely recognized by the late nineteenth century (Peckhaus 2012)). Leading figures in such developments were Frege, Hilbert, Whitehead, Russell and Wittgenstein.
Russell led the application of the new method of analytic philosophy that required solving or dissolving philosophical problems by analyzing their formulation in a more perspicuous technical, logical language. His student Wittgenstein, in turn, introduced a linguistic philosophy that limited the world to the scope of the application of an ideal symbolic languages, or calculus. As a result, the sole task of philosophy was, according to Wittgenstein, the critique of language in the form of an activity of clarification, without yielding a distinctive philosophical body of knowledge or set of propositions.
Looking to the rationalist traditions of Descartes and Leibniz, Jean van Heijenoort and Jaakko Hintikka have distinguished between two views of language that are relevant to the new linguistic turn (Mormann 1999): language as calculus (LC) and language as universal medium (LUM). The LC tradition, illustrated by Tarski’s views, aligned itself with the Cartesian ideal of a transparent language, with clear and distinctive meaning and explicit, mechanical combination and rule-following that extended to its use in reasoning. There are many possible constructed languages and each is an interpreted calculus with different possible semantics. The LUM tradition adopted the idea of a single actual or ideal language and one semantic or interpretation, to be elucidated, with no possibility of representing its relation to the world from outside. Views by Frege, who pointed to Leibniz on language and reasoning, and Wittgenstein illustrate this tradition, which in turn accommodates two versions, a Cartesian one (Frege and Russell) and a non-Cartesian one (Wittgenstein).
Members of the Vienna Circle pursued their shared philosophical goals through the discussion of language and its application in cognition. Their respective views on epistemic matters relied on different views on language and philosophy. Carnap and Neurath shared an epistemological naturalism –without a priori foundations– with a constructive metascientific standpoint; philosophy would require a scientific metatheory within the boundaries of unified science (Uebel 2007 and Bentley 2023). The difference rested in the goals and scientific disciplines they favored. Carnap looked to formal tools such as logic and syntax and sought rational reconstruction; Neurath looked to the empirical sciences, from psychology to history and sociology and sought pragmatic guidance to provide and improve scientists’ tools and decisions –and social applications.
Carnap’s conversion to semantics in the early 1930s took him to the LC Cartesian tradition seeking a universal language of rational reconstruction he had previously recognized in the language of physics. Neurath, by contrast, modeled his anti-metaphysical unification of the sciences in the LUM tradition, on a public –empirically testable and socially effective– universal mixed language he eventually called a ‘universal jargon’, with descriptions of spatio-temporal arrangements and connections he called physicalism, historically contingent use of vague and ordinary terms (see below). In this context Neurath adopted a militant syntacticism, avoiding semantic entities and properties such as truth-values, reference and correspondence. He unsurprisingly opposed and denounced Carnap’s defense of semantics and Schlick’s talk of reality as metaphysical (Anderson 2019) –engaging along the way in heated terminological disputes that ignored Carnap’s commitment to ontological neutrality (Carus 2019).
Again, the Circle’s projects shared the aforementioned focus on language and experience. The linguistic approach was adopted as a philosophical tool in order to explicate the rationality and the objectivity—that is, inter-subjectivity—and communicability of thought. Lacking the transcendental dimension of Kant’s metaphysical apparatus, attention to language extended to non-scientific cases such as ‘ordinary language philosophy’ in Oxford. In the context of logical empiricism, the formal dimension of knowledge was thought to be manifest particularly in the exactness of scientific statements.
For Schlick, knowledge proper, whether of experience or transcendent reality, was such only by virtue of form or structure—‘only structure is knowable’. For Carnap, in addition, the formal dimension possessed distinct methodological values: it served the purpose of logical analysis and rational reconstruction of knowledge and helped expose and circumvent ‘pseudo-philosophical’ problems around metaphysical questions about reality (his objections to Heidegger appealed to failures of proper logical formulation and not just empirical verification). In 1934 he proposed as the task of philosophy the metalinguistic analysis of logical and linguistic features of scientific method and knowledge (the ‘thesis of metalogic’). For Neurath, this approach helped purge philosophy of deleterious metaphysical nonsense and dogmatism, and acknowledged the radically social nature of language and science. His approach to demarcation through significance or meaningfulness was pragmatic and looser than that of fellow Circle members. His approach to verification, or empirical control, and formal control of knowledge claims was contextual, pragmatic and holistic. He defended a corresponding distinction between controlled, integrated statements (unification) and uncontrolled, isolated metaphysical ones –or of some other kind. But this required a uniform language for scientific collaboration that he thought contained unavoidable vague terms and required uniform notational standards, even in logic.
Neurath’s plan was for a unified science against metaphysics, and this involved a plan to police the proper unifying, metaphysics-free language. The negative track of the plan was effectively carried out by the development and adoption of a list of ‘dangerous terms,’ which he sometimes referred to, semi-jokingly, as an index verborum prohibitorum: a list of forbidden terms such as ‘I’, ‘ego’, ‘substance,’ etc. (Neurath 1933, Neurath 1940/1984, 217). The positive track was the adoption of the universal language of physicalism: ‘metaphysical terms divide—scientific terms unite’ (1935, 23, orig. ital.).
3.2 Language, logic and rationality
Logic has long received philosophical attention as a language regulated by strict rules of reasoning, thus setting standards of clarity, rigor and rationality. Leibniz had given modern philosophical currency to the pasigraphic notion of a universal characteristic or Alphabet of Thought that both expressed reality and operated as a logical calculus of reasoning. In the Cartesian spirit, language and reason were inseparable instruments of knowledge and mathematical, logical and philosophical methods were identical. In the late nineteenth century and the early twentieth, Leibniz’s project became a common reference in works in mathematical logic. Not only did Frege see his philosophy of language and mathematical logic within this tradition, as did Peano; Russell penned a landmark study and logicians such as Ernst Schröder and Louis Couturat associated it distinctively with the development of algebraic logic since Boole, especially with Schröder’s own (Peckhaus 2012).
Neurath enjoyed early attention and recognition for his logic work also reflected in early reminiscences of figures such as Popper and the mathematician Karl Menger. Perhaps surprisingly now, mentions of Neurath’s and Olga Hahn’s papers were included by the logicians C.I. Lewis, in 1918, and Alonzo Church, in 1936, in their canonical bibliographies on symbolic logic (Lewis 1918 and Church 1936). Neurath kept algebraic logic and its symbolic dimension as a recurrent standard and resource, first in his earlier work on the social sciences and pictorial language, and subsequently in related contributions to the discussions that informed logical empiricism.
Contrary to predominant accounts using attention to formal languages and logic to pit against each other wings and members of the logical empiricist movement, the symbolic logical standard may be considered a unifying framework for scientific philosophy that distinguished Neurath within it and not from it. It a unifying reference he willingly adopted when he coined the term ’logical empiricism.’ The differentiating role in Neurath’s positions can be identified in his shifting and progressively skeptical and critical attention to the standard and to his attention to algebraic logic rather than the newer logic familiar to Carnap from Frege’s and Russell’s works on logic and logicism.
By the late nineteenth century, in Austria as well as Germany, algebraic logic had found a central place in the raging controversies over the relationship between science and philosophy and, in particular, between mathematics, logic and psychology. Neurath and Olga Hahn became acquainted with algebraic logic at the University of Vienna sometime around 1902–3, but it wasn’t until 1909, after Olga had become blind and Neurath was back in Vienna providing assistance, that she started working on algebraic logic for her doctorate in philosophy and they began their collaboration and separate publications. Neurath published four papers, one with Hahn (Neurath 1909a, 1909b and 1910a, and Hahn and Neurath 1909). Hahn separately published two others, the second submitted as her doctoral thesis (Hahn 1909 and 1910).
Neurath’s logic writings focused on Schröder’s axiomatic systematization of algebraic logic, mainly in the monumental Vorlesungen über die Algebra der Logik (exakte Logik) (1890–95). There and in earlier writings, Schröder gave a fundamental role to the relation of subsumption and a law of duality. Subsumption was a part-whole relation defined over domains of objects. The law of duality established a systematic correspondence between theorems in terms of 1 and operation + and theorems in terms of 0 and operation x.
The papers were concerned with the equality relations and fundamental status of axioms of the system of algebraic logic, dominant in the second half of the nineteenth century and modeled, they objected, too closely after mathematical operations and equations. It was developed as a calculus of statements (propositional logic) and domains, more generally. Neurath distinguished between expression and denotation of signs to distinguish different uses and interpretations of equality signs and interpret symbolic identities as univocal relations and redundant expressions and rules of substitution in the logical manipulation of signs. In particular, he distinguished between definitional equality, symbolic equality and identity equality. Most of the papers focused on the case of the property of commutativity (‘ab=ba’) and Schröder’s proof. Neurath rejected the proof as based on unjustified mathematical notational assumptions. In particular, the symbolic equality between symbols for the same relation between the same objects renders one symbol meaningless, or redundant. The commutativity result is merely a symbolic equality, a notational stipulation.
In their joint paper, Hahn and Neurath also focused on the principle of duality as a basic symmetry principle for the generation of theorems for complementary domains and operations. They argued that duality is linked to the fundamental symmetric complementarity between positive and negative domains. It is a (meta)logical, not an empirical, inductive principle; so understood it could be applied more clearly and systematically. Neurath and Hahn’s attention to the relativity of fundamental logical axioms and symbolic notation paralleled similar conventionalist discussions in geometry, especially by Poincaré.
Rational decision-making became a central issue in Neurath’s economic thinking. All the more so when Neurath noted the limitations of the calculation of collective comparative pleasure and displeasure associated with different sets of goods (Neurath 1912). It is hardly surprising then that, even before engaging in debates over the rationality of socialist economic planning, Neurath continued examining reasoning and rationality –theoretical and practical– more generally. In Vienna, the intellectual and social project was connected to the spirit of the Enlightenment. In an essay of 1913, ‘The lost wanderers of Descartes and the auxiliary motive (on the psychology of decision)’ (Neurath 1913) he criticized Descartes’ theoretical rationalism and examined his psychology of action to explore decision-making under uncertainty. He introduced a general distinction, for theoretical and practical reasoning, between rationality and pseudo-rationalism. He dismissed as pseudorationalism the ideal of replacing instinct and authority with formal reasoning and calculation as the sole and sufficient method of decision-making based on conclusions without awareness of cognitive limitations or incomplete insight.
Instead, he argued, conclusions about courses of action, including the acceptance of hypotheses, are typically in need of supplementing with additional considerations he called auxiliary motives. The recourse is justified pragmatically. In general, what counts as an auxiliary motive might be external motives, values or conventions (goals or constraints as reasons) and pure decision procedures including the drawing of lots –since making any decision is more important than any decision made– (on the pure proceduralist interpretation see Bentley 2023). This volutntarism, decisionism and pragmatism became central to his contributions to the scientific epistemology of logical empiricism. He referred then also to unavoidable extra-logical factors (Neurath 1934).
3.3 Scientific and linguistic epistemology
Kant had delivered the latest grand attempt to address the relation between science and philosophy, by taking the former to provide objective empirical knowledge (exact, universal and necessary) and giving to the latter knowledge the task of laying out the a priori conditions of intelligibility and possibility of such knowledge as the sole, critical scope of metaphysics and legitimate exercise of reason. Kant’s standard of a priori, an expression of rationality, was challenged and relativized by Frege, Russell and Whitehead’s notions of mathematical numbers grounded in logic, by models of non-Euclidean geometry and their analysis by Poincaré and by the new notions of space and time in Einstein’s relativity theories. Neither mathematics was synthetic nor physics seemed a priori; as a result, in the new scientific landscape the metaphysical category of synthetic a priori was dismissed as empty of content.
With the scientific world-conception, logical empiricists followed in the footsteps and Helmholtz and Mach and considered a new post-Kantian problematic: investigating the possibility of objective empirical knowledge with a role for intellectual construction without universality or necessity, neither Kantian apriorism nor radical positivism. Logic, with scientific status linked to technical symbolism and the possibility of mathematics, was the sole last refuge for philosophy. The new problematic suggested a demarcation project with two inseparable tasks that were both descriptive and normative: a positive, unifying task to establish and promote the marks of scientific knowledge and the negative task to distinguish it from philosophy, especially the objects and concepts of metaphysics.
According to logical empiricists a priori knowledge claims expressed in exact theory were circumscribed to the analytic. Yet they were voided of universality and necessity (Kant’s marks of the a priori) and deflated by Schlick and Reichenbach to the character of definitions and conventions (following Poincaré). They were true or valid only relatively and by construction. Synthetic knowledge claims were exclusively a posteriori, their contents and validity grounded in experience.
The philosophical discussion that developed around the members of the Vienna Circle was associated with the formulation of logical empiricism and the rallying cry of ‘unity of science against metaphysics.’But it cannot be adequately understood without taking into account the diversity of evolving projects it accommodated. Carnap’s and Neurath’s respective metascientific stance has been mentioned above. Carnap was much borrowed from the neo-Kantian tradition, Einstein’s theories of relativity, Husserl’s phenomenology, Frege’s logic and, i.e., Hilbertian axiomatic approach to mathematics as well as Russell’s own logicism and his philosophical project of logical constructions. He was concerned with the conditions of the possibility of objective knowledge, which he considered especially manifest in the formal exactness of scientific claims (Carnap 1928). Schlick borrowed from turn-of-the-century French conventionalists such as Rey, Duhem and Poincaré, Wittgenstein’s philosophy of representation of facts, as well as Einstein’s relativity theories and Hilbert’s implicit definitions and axiomatic approach to mathematics. He was interested in the meaning of terms in which actual scientific knowledge of reality is expressed, as well as its foundation on true and certain beliefs about reality (Schlick 1918, 1934). Also Reichenbach had been influenced by and borrowed from Einstein, neo-Kantianism and Hilbert’s axiomatics. Neurath borrowed, among others, fromm Mach, varieties of French conventionalism, especially Duhem’s, and varieties of social thought including Marxism. He sought to explore the empirical and historical conditions of scientific practice in both the natural and social sciences (Neurath 1931/1973, 1932a/1983). Outside the Vienna Circle, Popper borrowed from Hume, Kant and Austrian child psychology. He was interested in addressing the logical and normative issues of justification and demarcation of objective and empirical scientific knowledge, without relying on descriptive discussions of the psychology of subjective experience and meaning (Popper 1935/1951).
The linguistic turn framed the examination of the controversial role of experience and the form of its expression and relation to hypotheses. In that respect an ensuing discussions of data or so-called protocol sentences concerned their linguistic characteristics and their epistemological status (Uebel 1992). It served the Circle’s purpose of ascertaining the source, evaluation and acceptance of human knowledge and rejecting metaphysics as nonsense—often dangerous nonsense (Carnap, Hahn and Neurath 1929/1973, and Stadler 2007).
Neurath’s departing position was a critique of Carnap. In his classic work Der Logische Aufbau der Welt (1928) (known as the Aufbau and translated as The Logical Structure of the World), Carnap investigated the logical ‘construction’ (Russell’s term) of objects/concepts of inter-subjective knowledge out of the simplest starting point or basic types. To reconstruct empirical knowledge, Carnap explored an empiricist, or phenomenological, model in terms of the immediate experiential basis was quickly understood by fellow members of the Vienna Circle as manifesting three philosophical positions that structured the debate: reductionism, atomism and foundationalism.
Reductionism took one set of terms to be fundamental or primitive; the rest would be logically connected to them.
Atomism, especially in Neurath’s reading, was manifest semantically and syntactically: semantically, in the analyzability of a term; syntactically or structurally, in the elementary structure of protocols in terms of a single experiential term—‘red circle here now.’ It appeared further in the possibility of an individual testing relation of a theoretical statement to one of more experiential statements.
Foundationalism, in the Cartesian tradition of a secure basis, took the beliefs in these terms held by the subject to be infallible, or not requiring verification, and the sole empirical source of epistemic warrant—or credibility—for all other beliefs. Descartes’s foundationalism is based on a priori knowledge; Carnap’s presentation of the empirical basis constitutes a more modest, naturalistic version (see also his 1932/1987).
Neurath first confronted Carnap on yet another alleged feature of his system, namely, subjectivism. On this issue dovetailed Carnaps’ Kantian problematic of explicating the objectivity of empirical knowledge and Neurath’s materialism and social –and socialist– perspective on economic, political and epistemic matters. Neurath rejected Carnap’s proposals on the grounds that if the language and the system of statements that constitute scientific knowledge are intersubjective, then phenomenalist talk of immediate subjective, private experiences should have no place. More generally, Neurath offered a private language argument, featuring Robinson Crusoe, to the effect that languages are necessarily intersubjective:
The universal jargon…is the same for the child and for the adult. It is the same for a Robinson Crusoe as for a human society. If Robinson wants to join what is in a protocol of yesterday with what is in his protocol today, that is, if he wants to make use of language at all, he must make use of the ‘intersubjective’ language. The Robinson of yesterday and the Robinson of today stand precisely in the same relation in which Robinson stands to Friday…In other words, every language as such is intersubjective. (Neurath 1932b/1983, 96)
To replace Carnap’s phenomenalist language Neurath introduced in 1931 the language of physicalism (Neurath 1931/1983 and 1932a/1983). Physicalism is, for Neurath, the view that the unity, intelligibility and objectivity of science rest on using statements in a language of public things, events and processes in space and time —including behavior and physiological events, hence not necessarily in the technical terms of physical theory. Carnap promptly adopted a more technical version of physicalism requiring translatability of protocols to the language of physics (Carnap 1932/1934). While inspired by anti-metaphysical materialism, for Neurath this was a methodological and linguistic rule, and not an ontological thesis. The syntacticism mentioned above concerns the emphasis on spatio-temporal order or patterns. Neurath’s view could claim that language was itself was a physical process and could express its own spatio-temporal structure. This was also in line with his typographic concerns in logic and visual communication.
That physicalism was to avoid metaphysical connotations can be seen further in that its linguistic nature was also central to its applications. Neurath insisted that statements can be compared only with statements, certainly not with some “reality”, nor with “things,” (Neurath 1931/1983, 53). Knowledge was a social matter of empirical control.
Neurath responded with a new doctrine of protocol statements that considered their distinctive linguistic form, contents and methodological status (Neurath 1932b/1983). This doctrine was meant to explicate the idea of scientific evidence in the framework of empiricism, and it did so by specifying public conditions of evaluation and acceptance of a statement as empirical scientific evidence. In particular, Neurath intended the physicalist doctrine of protocol statements to circumvent the pitfalls of subjectivism, atomism, reductionism and foundationalism attributed to Carnap’s earlier discussion. It supported, instead, a holistic, anti-foundationalist, decisionistic, pragmatist, social view characterizing the scientific, empiricist attitude.
One informal but paradigmatic example of a protocol was:
Otto’s protocol at 3:17 o’clock: [Otto’s speech-thinking at 3:16 was: (at 3:15 o’clock there was a table in the room perceived by Otto)].
Neurath offered examples over time featuring different numbers of parts, between two and four (on the debate around this issue, see Uebel 2007). Far from Carnap’s atomic sort of protocol statements, Neurath’s model manifested a distinctive complexity of terms and structure. The protocol contains a factual physicalist core in terms about the table and its location. It also contains the experiential term that provides the linguistic recording of the empirical character of protocols, that is, their experiential origin. Neurath was mindful to caution here that perception terms only admitted physicalistic meaning in terms, for instance, of behavior or physiological mechanisms of perception. It also contains the declarative level, marked with ‘Otto says’, which distinguishes the protocol as a linguistic statement. Finally, the other distinctive elements were the name of the protocolist and the times and locations of the experience and the reports, which provided an intersubjective, physicalist, public alternative to Carnap’s first-person, subjective ‘I see a red circle here now’.
Unlike Carnap’s ideal of basic statement, whether protocol or physicalist, Neurath’s protocols were not ‘clean’, precise or pure in their terms. For Neurath physicalist language, and hence science in turn, is inseparable from ordinary language of any time and place. In particular, it is muddled with imprecise, unanalyzed, cluster-like terms (Ballungen) that appear especially in the protocols: the name of the protocolist, ‘seeing’, ‘microscope’, etc. They were often to be further analyzed into more precise terms or mathematical co-ordinations, but they often would not be eliminated. Even the empirical character of protocol statements could not be pure and primitive, as physicalism allowed the introduction of theoretical—non-perception—terms. Physicalism, and thus unified science, were based on a universal ‘jargon’.
Neurath’s protocols didn’t have the atomic structure and the atomic testing role of Carnap’s. Their methodological role reflected Duhem’s holism: hypotheses are not tested individually; only clusters of statements confront empirical data. But their methodological value in the testing of other statements didn’t make them unrevisable. This is Neurath’s anti-foundationalism: Insofar as they were genuinely scientific statements, consistency with the spirit that opposed science to dogmatic speculation and, no less importantly, opposed naturalistic attention to actual practice, required that protocols too be testable. Physicalism challenges the epistemic authority of first-person private experience and enables the democratic socialization of empirical claims in the networks of scientific statements and collaborations.
From this follows the so-called Neurath Principle: in the face of conflict between a protocol and theoretical statements, the cancellation of a protocol statement is a methodological possibility as well (Neurath 1932b/1983, Haller 1982). The role of indeterminacy in the protocol language points to a distinction between a special Neurath Principle and a general Neurath Principle (Cartwright et al. 1996, Cat 1995). In the former, and earlier, Neurath assumed a determinate logical relation of inconsistency. In the latter, subsequent version, the scope of relations between hypotheses and protocol statements extended to indeterminate relations such that the principle behind the epistemic status of protocol statements is simply grounded on the voluntaristic and conventionalist doctrine that ‘[a]ll content statements of science, and also their protocol statements that are used for verification, are selected on the basis of decisions and can be altered in principle’ (Neurath 1934/1983, 102).
The complex structure of the explicitly laid out protocol would provide an explication and synoptic visual tool for differentiating and integrating explicitly relevant testing conditions: the intersubjective conditions of evaluation and acceptance of the record and its core data, or record of core factual information to enter the relevant scientific field of empirical research. The different conditions could guide the control of relevant data by laying out the conditions of their origin, validity and fallibility (was Otto hallucinating? were all the parts of the experimental instrument working reliably? etc.).
Neurath’s dictum was meant to do justice to actual scientific practice and its normative standards with regards to the role of experimental data. It is up to the members of the scientific community to decide when a protocol can support or challenge a hypothesis, at last provisionally. Invalid protocols may change their status or be repurposed as data for historical or social studies of science (Uebel 2007 and Bentley 2023). What distinguishes the epistemic status of protocol sentences is not their foundational certainty (unlike for Schlick), but their stability as available and acceptable records over time and across projects and purposes. In this way they facilitate communication, cooperation and empirical inquiry.
The method of testing failed to meet a certain standard and expectation of rationality: It could not be carried out in a logically precise, determinate and conclusive manner. expecting calculability, determinism, omniscience and certainty (Neurath 1913/1983, Neurath 1934/1983 and Cat 1995). By virtue of perception terms, protocol sentences could in fact provide certain stability in the permanence of information necessary for the generation of new expressions. But methodologically they could only bolster or shake our confidence. To acknowledge these limitations is a mark of proper rationality—which he opposed to pseudorationality.
A loose coherentist view of warrant, acceptance and unification is the only logical criterion available: ‘a statement is called correct if it can be incorporated in this totality’ of ‘existing statements that have already been harmonized with each other’ (Neurath 1931/1984, 66). Reasons underdetermine our actions and thus pragmatic extra-logical factors are required to make decisions about what hypotheses to accept. Thinking requires provisional rules, or auxiliary motives, that fix a conclusion by decision (Neurath 1913/1983).
Scientific rationality is situated, contextually constrained by, practical rationality. The construction of knowledge is constrained by historically, socially, methodologically and theoretically accepted claims and standards –as well as other possible factors he called extra-logical. They bear limited stability, and cannot be rebuilt on pure, secure, infallible empirical foundations. This is the anti-Cartesian naturalism, non-foundationalism, fallibilism and holism of Neurath’s social model. This is also the basis for its corresponding decisonistic, conventionalist, constructivist normativity (Uebel 1996 and 2007 and Cartwright et al. 1996). Without the norms and conventions self-issued within a community, there is no possibility of rationality or objectivity of knowledge. Neurath captured the main features of his doctrine of scientific knowledge in the image of a boat:
There is no way to establish fully secured, neat protocol statements as starting points of the sciences. There is no tabula rasa. 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 its best components. Only metaphysics can disappear without a trace. Imprecise ‘verbal clusters’ [Ballungen] are somehow always part of the ship. If imprecision is diminished at one place, it may well re-appear at another place to a stronger degree. (Neurath 1932b/1983, 92)
Just like Neurath debated Carnap, he also entered an acrimonious debate with Popper and Schlick. By 1934, the year of the completion of his Logic of Scientific Discovery (Logik der Forschung), Popper had adopted an approach to scientific knowledge based on the logic of method, not on meaning, so that any talk of individual experience would have no linguistic expression(Popper 1935/1951). He was concerned with the post-Kantian problematic of the rational objective validity of scientific knowledge claims.
Instead of protocols, Popper proposed to speak about basic statements—a term more attuned to their logical and functional role. They are basic relative to a theory under test. Their empirical character would invisibly reside in the requirement that basic statements be singular existential ones describing material objects in space and time—much like Neurath’s physicalism—which would be observable, in a further unspecified logical not psychological sense. Their components would not themselves be purely empirical terms since many would be understood in terms of dispositional properties, which, in turn, involved reference to law-like generalizations. But their ‘basic’ role was methodological ‘with no direct function of demarcation from metaphysics in terms of meaning, sense or cognitive significance’ and only provisional. They would be brought to methodological use for the purpose of falsifying theories and hypotheses ‘individually and conclusively’ only once they were conventionally and communally accepted by decision in order to stop infinite regress and further theoretical research.
But such acceptance, much as in Neurath’s model, could be in principle revoked. It is a contingent fact that scientists will stop at easily testable statements simply because it will be easier to reach an agreement. It is important that basic statements satisfy explicit conditions of testability or else they could not be rightful part of science. Popper could offer no rational theory of their acceptance on pain of having to have recourse to theories of psychology of perception and thereby weakening his normative criterion of demarcation. In his view, his method, unlike Neurath’s, didn’t lead to either arbitrariness or dogmatism or the abandonment of empiricism. As he had argued against Spengler in 1921, historical contingency provides the rich constraints that establish communities and communication and the possibility of knowledge and, in this holistic form, preclude radical relativism in practice; in historically situated practice, inherited or constructed stable Archimedean points always come into place; there is no tabula rasa (Neurath 1921/1973). Neurath rejected Popper’s approach for its stealth empiricism and its pseudorationalism: its misplaced emphasis on and faith in the normative uniqueness, precision and conclusiveness of a logical method—at the expense of its own limitations and pragmatic character (Zolo 1989, Cat 1995, Hacohen 2000).
Finally, the most radical empiricist attitude toward protocol sentences within the Vienna Circle came from Schlick. Schlick endorsed, following Hilbert, a formal, structural notion of communicable, objective knowledge and meaning as well as a correspondence theory of truth. His realism opposed Neurath’s coherentism, and also the pragmatism and conventionalism of Carnap’s Principle of Tolerance in logical matters, as well as his Thesis of Metalogic. But like Carnap’s latter thesis and his syntactic approach of 1934, Schlick was concerned with both the Cartesian ideal of foundational certainty and Wittgenstein’s metalinguistic problem of how language represents the reality it is about; such relation could only be shown, not said. In 1934 Schlick proposed to treat the claims motivating protocol statements, left by Neurath with the status of little more than mere hypotheses, as key to the foundation of knowledge. They would be physicalistic statements that, albeit being fallible, could be subjectively linked to statements about immediate private experiences of reality such as ‘blue here now’ he called affirmations (Konstatierungen) (Schlick 1934).
Affirmations carried certainty and elucidated what could be showed but not said, they provided the elusive confrontation or correspondence between theoretical propositions and facts of reality. In this sense they afforded, according to Schlick, the fixed starting points and foundation of all knowledge. But the foundation raised a psychological and semantic problem about the longer-term acceptance of a protocol. Affirmations, as acts of verification or giving meaning, lacked logical inferential force; in Schlick’s words, they ‘do not occur within science itself, and can neither be derived from scientific propositions, nor the latter from them’ (Schlick 1934, 95). Schlick’s empiricism regarding the role of protocol sentences suggests but does not support strong epistemological foundationalism. Schlick’s occasional references to a correspondence theory of truth were just as unacceptable and were felt to be even more of a philosophical betrayal within the framework of empiricism. Predictably, Neurath rejected Schlick’s doctrines as metaphysical, manifesting the pseudorationalist attitude (Neurath 1934/1983).
https://plato.stanford.edu/entries/neurath/index.html
"Neurath was a social scientist and activist, scientific philosopher and maverick leader of the Vienna Circle who championed the so-called scientific attitude and the Unity of Science movement. He denied any value to philosophy over and above the pursuit of work on science, within science and for science and society. And scientific results, he argued, are not logically fixed, securely founded on experience or can be ordered in a System of knowledge. Uncertainty, decision and cooperation are intrinsic to scientific practice. From this naturalistic, holistic and pragmatist viewpoint, philosophy investigates the conditions of the possibility of science as apparent in science itself, namely, in terms of physical, biological, sociological, historical, psychological, linguistic, logical or mathematical conditions. His views on the language, method and unity of science were led throughout by his interest in the social life of individuals and their well-being. To theorize about society is inseparable from theorizing for and within society. Science is in every sense a social and historical enterprise and helps society understand the past, explore possibilities and engineer the future. It is as much about social objectives as it is about physical objects, and about social realizations as much as about empirical reality. Objectivity and rationality, epistemic values to constrain scientific thought, were radically social. His contributions to visual education –based on pictorial languages–, museology, urban planning, and political economy –especially on collective welfare, ecological economics and the unavoidability of multi-criterial evaluation– constitute concrete legacies that have regained relevance, interest and urgency.
Otto Neurath was born on 10 December 1882 in Vienna. He was the son of Gertrud Kaempffert and Wilhelm Neurath, a Hungarian Jewish political economist and social reformer. While benefitting from his father’s vast polymathic library, in Vienna he studied literature, mathematics, physics, history, philosophy and economics (although he formally enrolled at the University of Vienna only for two semesters in 1902–3). Next he followed the social scientist Ferdinand Tönnies’s advice to move to Berlin, where he received a doctoral degree in history of economics in 1906. He studied under leaders of the so-called Young German Historical School Eduard Meyer and Gustav Schmoller and he was awarded the degree for two studies of economic history of antiquity, one on Cicero’s De Officiis and the other with an emphasis on the non-monetary economy of Egypt.
On his return to Vienna, he joined other economists such as Joseph Schumpeter and Ludwig von Mises at postdoctoral seminars led by theoriests of Carl Menger’s so-called Austrian School Eugen von Böhm-Bawerk and Friedrich von Wieser. At the time Neurath engaged ongoing debates over the unity of the sciences –especially the distinction between Naturwissenschaften and Geisteswisshenschaften–, the role of values in science and goals and methods of economics (Uebel 2004). The debates would prompt early views on the practice of science and inform his subsequent positions within scientific philosophy and logical empiricism.
His first publications were in the history of political economy and logic, a subject he had formally learned at the University of Vienna. In the history of political economy, topics included the history of money and economic organizations in antiquity, and his publications included textbooks and readers either co-authored or co-edited with his first wife Anna Schapire-Neurath, expert in literature and social issues. The papers on logic focused on issues in algebraic logic and included one paper, of 1909, co-authored with his friend and second wife, Olga Hahn, a sister of the mathematician Hans Hahn (she shortly after received a doctorate for her logic work). Neurath’s subsequent theorizing on the social sciences and his contributions to debates on logical empiricism integrated both disciplines. With the mathematician Hans Hahn and the physicist Philip Frank, around 1910 Neurath formed in Vienna a philosophical discussion group focused on foundational crises in physics and mathematics and the philosophical ideas about science of Vienna’s positivist Ernst Mach and the French conventionalists Pierre Duhem, Abel Rey and Henri Poincaré. A great deal of philosophical and scientific concerns and insight were already in place in Neurath’s thinking and projects. With a grant from the Carnegie Endowment for International Peace, a subsequent study of the Balkan Wars and then World War I led him to develop a theory of war economy as a natural (non-monetary) economy, or economy in kind, and to propose models for its peacetime implementation as a solution to endemic socio-economic problems of capitalism.
In 1919 the short-lived Bavarian socialist government (November 1918-April 1919) appointed him head of the Central Planning Office. The fall of the subsequent Bavarian Soviet Republic in May 1919 got him expelled from his junior post teaching economic theory under Max Weber at Heidelberg University, where he had received his Habilitation in 1917. His program for full socialization of the economy was inspired by his studies of war economics and based on his theory of natural economy and a holistic requirement to bring different institutions and kinds of knowledge together in order to understand, predict and control the complex phenomena of the social world (see the supplementary material on Political Economy). His driving social concern was collective welfare or happiness, which he came to consider not a form of utiltarianisn but of Epicurean socialism.
From 1921 until 1934 Neurath participated actively in the development of socialist politics, especially in housing and adult education, in so-called Red Vienna (on his political life, see Sandner 2014). He established the Social and Economic Museum of Vienna, where he developed and applied the ‘Vienna method’ of picture statistics and the ISOTYPE language (International System of Typographic Picture Education) (see the supplementary document on Visual Education). Like the thought of other Viennese philosophers such as Ludwig Wittgenstein and Karl Popper, Neurath’s philosophy was inextricably linked to pedagogy, logic, critique of language and, in Popper’s case, political thought. In 1928, with members of the Austrian Freethinkers Association and the Vienna City Council and the scientifically-trained members of the informal circle around the current holder of Mach’s University Chair, the philosopher Moritz Schlick (1924–29), Neurath helped found the Verein Ernst Mach, the Ernst Mach Association for the Promotion of Science Education. The publication in 1929 of an intellectual manifesto gave way to the formation of the Vienna Circle, whose narrower goal was the articulation and promotion of a scientific world-conception and logical empiricism (on the Viennese intellectual landscape, see Stadler 2001).
When in 1934 the Austrian government allied itself with the German Nazi government, Neurath fled to the Netherlands. As a result, his local, Viennese, socialist Enlightenment project turned into an internationalist, intellectual and social-political project. He created the International Foundation for Visual Education in The Hague, with his assistants from Vienna, and spearheaded the International Unity of Science movement. The latter, inspired by a tradition culminating in the Enlightenment’s French Encyclopedists, launched the project of an Encyclopedia of Unified Science. Together with the pictorial languages, the scientific encyclopedia would promote scientific and social cooperation and progress at an international level. After Austria became part of the German Reich in 1938, even though living in the Netherlands, Neurath was considered a German citizen and a ‘half-Jew’ and he was not allowed to marry his ‘Aryan’ assistant Marie Reidemeister—after his second wife, Olga, had died in 1937. During this period, he travelled abroad, including the United States, where logical empiricism had become entangled with the Cold War political and intellectual debates and witch hunts (on the Cold War phase, see Reich 2005). Carnap and Charles Morris at the University of Chicago acted as his co-editors of the International Encyclopedia of Unified Science. New York leftist intellectuals hosted him as an intellectual and political ally. And his maternal first cousin Waldemar Kaempffert, influential editor for The New York Times and Popular Science, introduced him as an international reformer and visionary, praising his science-oriented intellectual, social and educational ideas, especially his contribution to unity of science and visual language (see Reisch 2019). After the Nazi invasion of the Netherlands in 1940, Otto Neurath and Marie Reidemeister fled to England, on the small Seaman’s Hope. After nine months in an internment camp they resumed activities related to the Isotype language, public education and the unity of science. He died in Oxford on 22 December 1945 (on activities in the camp see Henning 2019; on activities after see Körber 2019 and Tuboly 2019).
by 1910 Neurath had already been involved in debates on the issues of scientific unity and methodology. They were prompted by his research in economics as well as foundational issues in mathematics and physics and reading in positivism and conventionalism. His early metascientific, or philosophical, views developed along with his economic thinking and evolving historical context. In projects of socialized, planned economic reform and in his broader notion of economics, they featured interrelated concepts and concerns: unity, rationality, precision, possibility, planning, decision, control, construction –or engineering–, communication, coordination, history and their social dimensions and applications. The same issues –alongside illustrating references to boats and Robinson Crusoe– would later play a defining role in his epistemological and methodological contributions to logical empiricism (Nemeth 1991, Cat et al. 1991 and 1996 and Cat 2024).
For instance: (1) a notion of theorizing in natural and social sciences, including history, based on the historical exploration of combinatorial possibilities and models, past and future; (2) the application in the social sciences of empirical goals and methods of the natural sciences; (3) a unifying public (objective and testable) language for scientific data and hypotheses, with a private-language argument anticipating Wittgenstein’s own and also illustrated by the case of Robinson Crusoe; (4) the evaluation and choice of data and hypotheses characterized by a logical under-determination of hypotheses by data and the conventional and pragmatic aspect of rational decision-making and control (with a role for so-called auxiliary motives); (5) the historical, social, cooperative, planned and constructive (engineering) dimensions of scientific research (a ‘republic of scientists’); (6), connectedly, a holistic approach to scientific knowledge and its application in the form of encyclopedic unification without hierarchical systems as a tool for successful prediction and engineering of events in a complex world –an ‘encyclopedia model’, by establishing cross-connections among disciplines, as in a Crusonian archipelago: a ‘great, rather badly coordinated mass of statements’ in which at best ‘systems develop like little islands, which we must try to enlarge’ (Neurath 1936/1983, 153)–; and (7) the social relevance of scientific philosophy, especially the unification and demarcation of science against metaphysics.
Regarding unification, Neurath endorsed a broader notion of economics based on symbolic (or logical) rather than merely quantitative precision and a historical perspective that included the use of empirical methods and theoretical distinctions common in the natural sciences; the combination served the purpose of comparing and classifying past cases and future possibilities (Neurath 1910). In addition, Neurath’s proposal of a moneyless war economy sought to maximize human happiness rather than private profit, and was based on a set of incommensurable indicators rather than the uniform monetary measurement unit. An economic plan for a socialized economy required the consideration of the different indicators that in turn required a holistic organization of information and individuals to coordinate decisions and action (rather than a market). Prediction and action required different forms of unity.
This engineering value of unity applied equally to political governance and scientific action, since both are collective and pragmatic endeavors. According to Neurath, ‘scientific theories are sociological events’ (Neurath 1932a/1983, 88), and, since ‘our thinking is a tool’, in this case the ‘modern scientific world-conception’ aims to ‘create a unified science that can successfully serve all transforming activity’ (Neurath 1930/1983, 42). In both cases, Neurath noted, ‘common planned action is possible only if the participants make common predictions’ and group predictions yield more reliable results; therefore, he concluded, ‘common action presses us toward unified science’ (Neurath 1931/1973, 407). Indeed, all along, for Neurath scientific attitude and solidarity (and socialism) go together (Neurath 1928/1973, 252).
Economic planning was a matter of consideration of possibilities and making rational decisions. But for Neurath, practical and theoretical rationality was not a matter of mechanical, objective calculation or reasoning alone –especially in the absence of full insight and a uniform quantitative monetary unit. In a study of psychology of decisions he dismissed such a standard of rationality as “pseudo-rationalism” (Neurath 1913). Planning was a pragmatic (social) engineering problem, namely, a matter of construction and control, and decisions among alternative possibilities that required judgement, external goals or just a coin flip –auxiliary motives (Neurath 1913). Both rationality and the irreducibly social perspective were matters of debate among economists, including Karl Marx, and illustrated, also by Neurath, with references to the fictional figure of Robinson Crusoe stranded on an island.
Along similar lines, we can place Neurath’s contributions to the Vienna Circle’s project of a scientific world-conception and logical empiricism in context of his evolving political epistemology. Considerations of knowledge at the theoretical or practical service of politics played a central role in his work on economic planning. He envisioned the role of rationality and the coordination of information and political goals mentioned above also in relation to socialist democratic model of participation of citizen workers. Deliberation and decision making required communication, also of social and economic information. For such education purpose, at the service of participation, Neurath designed a pictorial language (Sandner 2014, Groß 2019 and Nemeth 2019; see also supplementary material on visual education). This discursive approach to communication of knowledge and decision making was also part of his objection and alternative to models such as Hayek’s based on the role of markets and prices (Hayek 1935, Neurath 1942). Neurath’s economic planning was neither technocratic nor dictatorial (Chaloupek 2008). But it relied on expert proposals.
In exile in the 1940s the socialist internationalism of his social models turned more liberal, combining international planning for freedom and liberal democracy. Neurath addressed the role of experts and the distinction between esoteric and exoteric, or lay, knowledge and promoted the democratization of knowledge: ‘what we call democracy implies a rejection of experts in making decision[s]’ (Neurath 1996, 251). But how much democratization required or could achieve in such checks on expert power has been debated (Wussow 2021).
Neurath formulated his empiricist epistemology through the 1930s in similar terms of checks and controls. Data statements he called control statements; and the dynamics of knowledge formation and revision was a matter of formal and empirical controls. Relative to the resulting unity in a theory or body of knowledge, metaphysical statements could be identified and rejected as uncontrolled and isolated
3.1 Language
Neurath’s later views on the language and method of science expressed his simultaneous response to earlier problems in the social sciences and to philosophical issues addressed by the Vienna Circle between 1928 and 1934. A primary aim of the Vienna Circle was to account for the objectivity and intelligibility of scientific method and concepts and to demarcate scientific from metaphysical statements. Their philosophical approach was to adopt what the Circle member Gustav Bergmann called the linguistic turn, namely, to investigate the formal or structural, logical and linguistic framework of scientific knowledge. Within this framework members of the Circle pursued the aims of intelligibility and demarcation by means of two connected conditions of meaning and meaningfulness. The former –stronger– often was formulated mainly by Moritz Schlick (after Wittgenstein) as a condition of empirical verification. The latter –weaker– was a related semantic condition of empirical verifiability, formulated mainly by Rudolf Carnap in different ways over time, and was supplemented by a syntactic condition of formal or grammatical correctness (Uebel 2007). The formal approach encompassed logicism and logical analysis as views about the formation, interpretation, justification and acceptance especially of theoretical statements. The problem of empiricism became then the problem of coordination between the formal theoretical structures and the records of observations in such a way that it also offered an explication of how scientific knowledge can and should be formally constructed (especially in logic and mathematics), empirically grounded (except logic and mathematics), and thereby understood, evaluated and accepted.
Sources of Neurath’s attention to language are multiple. Besides Neurath’s own early interest in logic and classical and ancient languages, the value of attention to language was familiar to Neurath from the Austrian fin-de-siècle culture of critique of language (Janik and Toulmin 1973), his interest (and his first wife’s) in literature, especially in Goethe (Zemplen 2006), Marx and Engels’ attention to the radically social dimension of language (and its relation to money), the internationalist and utopianists efforts at introducing new universal languages such as Volapük and Esperanto, the emphasis on signs and universal languages – to be known as pasigraphy – in the scholastic and rationalist philosophical traditions, in the traditions of empirical taxonomies and in the interest in universal language as instrument of knowledge and social order in the Enlightenment, a semiotic tradition in scientific epistemology including Helmholtz, Mach, Duhem and Peirce (Cat 2019) and the sociologist Ferdinand Tönnies’s formal approach to sociology and social signs (Tönnies 1899–1900 and Cartwright et al. 1996). The significance of the internationalist and philosophical projects of so-called pasigraphy were acknowledged also by Carnap. More “scientific” sources were recent technical developments in logic, philosophy of science and the foundation of mathematics often claiming Leibniz as a precursor (Leibniz’s logic and project of a universal characteristic had become widely recognized by the late nineteenth century (Peckhaus 2012)). Leading figures in such developments were Frege, Hilbert, Whitehead, Russell and Wittgenstein.
Russell led the application of the new method of analytic philosophy that required solving or dissolving philosophical problems by analyzing their formulation in a more perspicuous technical, logical language. His student Wittgenstein, in turn, introduced a linguistic philosophy that limited the world to the scope of the application of an ideal symbolic languages, or calculus. As a result, the sole task of philosophy was, according to Wittgenstein, the critique of language in the form of an activity of clarification, without yielding a distinctive philosophical body of knowledge or set of propositions.
Looking to the rationalist traditions of Descartes and Leibniz, Jean van Heijenoort and Jaakko Hintikka have distinguished between two views of language that are relevant to the new linguistic turn (Mormann 1999): language as calculus (LC) and language as universal medium (LUM). The LC tradition, illustrated by Tarski’s views, aligned itself with the Cartesian ideal of a transparent language, with clear and distinctive meaning and explicit, mechanical combination and rule-following that extended to its use in reasoning. There are many possible constructed languages and each is an interpreted calculus with different possible semantics. The LUM tradition adopted the idea of a single actual or ideal language and one semantic or interpretation, to be elucidated, with no possibility of representing its relation to the world from outside. Views by Frege, who pointed to Leibniz on language and reasoning, and Wittgenstein illustrate this tradition, which in turn accommodates two versions, a Cartesian one (Frege and Russell) and a non-Cartesian one (Wittgenstein).
Members of the Vienna Circle pursued their shared philosophical goals through the discussion of language and its application in cognition. Their respective views on epistemic matters relied on different views on language and philosophy. Carnap and Neurath shared an epistemological naturalism –without a priori foundations– with a constructive metascientific standpoint; philosophy would require a scientific metatheory within the boundaries of unified science (Uebel 2007 and Bentley 2023). The difference rested in the goals and scientific disciplines they favored. Carnap looked to formal tools such as logic and syntax and sought rational reconstruction; Neurath looked to the empirical sciences, from psychology to history and sociology and sought pragmatic guidance to provide and improve scientists’ tools and decisions –and social applications.
Carnap’s conversion to semantics in the early 1930s took him to the LC Cartesian tradition seeking a universal language of rational reconstruction he had previously recognized in the language of physics. Neurath, by contrast, modeled his anti-metaphysical unification of the sciences in the LUM tradition, on a public –empirically testable and socially effective– universal mixed language he eventually called a ‘universal jargon’, with descriptions of spatio-temporal arrangements and connections he called physicalism, historically contingent use of vague and ordinary terms (see below). In this context Neurath adopted a militant syntacticism, avoiding semantic entities and properties such as truth-values, reference and correspondence. He unsurprisingly opposed and denounced Carnap’s defense of semantics and Schlick’s talk of reality as metaphysical (Anderson 2019) –engaging along the way in heated terminological disputes that ignored Carnap’s commitment to ontological neutrality (Carus 2019).
Again, the Circle’s projects shared the aforementioned focus on language and experience. The linguistic approach was adopted as a philosophical tool in order to explicate the rationality and the objectivity—that is, inter-subjectivity—and communicability of thought. Lacking the transcendental dimension of Kant’s metaphysical apparatus, attention to language extended to non-scientific cases such as ‘ordinary language philosophy’ in Oxford. In the context of logical empiricism, the formal dimension of knowledge was thought to be manifest particularly in the exactness of scientific statements.
For Schlick, knowledge proper, whether of experience or transcendent reality, was such only by virtue of form or structure—‘only structure is knowable’. For Carnap, in addition, the formal dimension possessed distinct methodological values: it served the purpose of logical analysis and rational reconstruction of knowledge and helped expose and circumvent ‘pseudo-philosophical’ problems around metaphysical questions about reality (his objections to Heidegger appealed to failures of proper logical formulation and not just empirical verification). In 1934 he proposed as the task of philosophy the metalinguistic analysis of logical and linguistic features of scientific method and knowledge (the ‘thesis of metalogic’). For Neurath, this approach helped purge philosophy of deleterious metaphysical nonsense and dogmatism, and acknowledged the radically social nature of language and science. His approach to demarcation through significance or meaningfulness was pragmatic and looser than that of fellow Circle members. His approach to verification, or empirical control, and formal control of knowledge claims was contextual, pragmatic and holistic. He defended a corresponding distinction between controlled, integrated statements (unification) and uncontrolled, isolated metaphysical ones –or of some other kind. But this required a uniform language for scientific collaboration that he thought contained unavoidable vague terms and required uniform notational standards, even in logic.
Neurath’s plan was for a unified science against metaphysics, and this involved a plan to police the proper unifying, metaphysics-free language. The negative track of the plan was effectively carried out by the development and adoption of a list of ‘dangerous terms,’ which he sometimes referred to, semi-jokingly, as an index verborum prohibitorum: a list of forbidden terms such as ‘I’, ‘ego’, ‘substance,’ etc. (Neurath 1933, Neurath 1940/1984, 217). The positive track was the adoption of the universal language of physicalism: ‘metaphysical terms divide—scientific terms unite’ (1935, 23, orig. ital.).
3.2 Language, logic and rationality
Logic has long received philosophical attention as a language regulated by strict rules of reasoning, thus setting standards of clarity, rigor and rationality. Leibniz had given modern philosophical currency to the pasigraphic notion of a universal characteristic or Alphabet of Thought that both expressed reality and operated as a logical calculus of reasoning. In the Cartesian spirit, language and reason were inseparable instruments of knowledge and mathematical, logical and philosophical methods were identical. In the late nineteenth century and the early twentieth, Leibniz’s project became a common reference in works in mathematical logic. Not only did Frege see his philosophy of language and mathematical logic within this tradition, as did Peano; Russell penned a landmark study and logicians such as Ernst Schröder and Louis Couturat associated it distinctively with the development of algebraic logic since Boole, especially with Schröder’s own (Peckhaus 2012).
Neurath enjoyed early attention and recognition for his logic work also reflected in early reminiscences of figures such as Popper and the mathematician Karl Menger. Perhaps surprisingly now, mentions of Neurath’s and Olga Hahn’s papers were included by the logicians C.I. Lewis, in 1918, and Alonzo Church, in 1936, in their canonical bibliographies on symbolic logic (Lewis 1918 and Church 1936). Neurath kept algebraic logic and its symbolic dimension as a recurrent standard and resource, first in his earlier work on the social sciences and pictorial language, and subsequently in related contributions to the discussions that informed logical empiricism.
Contrary to predominant accounts using attention to formal languages and logic to pit against each other wings and members of the logical empiricist movement, the symbolic logical standard may be considered a unifying framework for scientific philosophy that distinguished Neurath within it and not from it. It a unifying reference he willingly adopted when he coined the term ’logical empiricism.’ The differentiating role in Neurath’s positions can be identified in his shifting and progressively skeptical and critical attention to the standard and to his attention to algebraic logic rather than the newer logic familiar to Carnap from Frege’s and Russell’s works on logic and logicism.
By the late nineteenth century, in Austria as well as Germany, algebraic logic had found a central place in the raging controversies over the relationship between science and philosophy and, in particular, between mathematics, logic and psychology. Neurath and Olga Hahn became acquainted with algebraic logic at the University of Vienna sometime around 1902–3, but it wasn’t until 1909, after Olga had become blind and Neurath was back in Vienna providing assistance, that she started working on algebraic logic for her doctorate in philosophy and they began their collaboration and separate publications. Neurath published four papers, one with Hahn (Neurath 1909a, 1909b and 1910a, and Hahn and Neurath 1909). Hahn separately published two others, the second submitted as her doctoral thesis (Hahn 1909 and 1910).
Neurath’s logic writings focused on Schröder’s axiomatic systematization of algebraic logic, mainly in the monumental Vorlesungen über die Algebra der Logik (exakte Logik) (1890–95). There and in earlier writings, Schröder gave a fundamental role to the relation of subsumption and a law of duality. Subsumption was a part-whole relation defined over domains of objects. The law of duality established a systematic correspondence between theorems in terms of 1 and operation + and theorems in terms of 0 and operation x.
The papers were concerned with the equality relations and fundamental status of axioms of the system of algebraic logic, dominant in the second half of the nineteenth century and modeled, they objected, too closely after mathematical operations and equations. It was developed as a calculus of statements (propositional logic) and domains, more generally. Neurath distinguished between expression and denotation of signs to distinguish different uses and interpretations of equality signs and interpret symbolic identities as univocal relations and redundant expressions and rules of substitution in the logical manipulation of signs. In particular, he distinguished between definitional equality, symbolic equality and identity equality. Most of the papers focused on the case of the property of commutativity (‘ab=ba’) and Schröder’s proof. Neurath rejected the proof as based on unjustified mathematical notational assumptions. In particular, the symbolic equality between symbols for the same relation between the same objects renders one symbol meaningless, or redundant. The commutativity result is merely a symbolic equality, a notational stipulation.
In their joint paper, Hahn and Neurath also focused on the principle of duality as a basic symmetry principle for the generation of theorems for complementary domains and operations. They argued that duality is linked to the fundamental symmetric complementarity between positive and negative domains. It is a (meta)logical, not an empirical, inductive principle; so understood it could be applied more clearly and systematically. Neurath and Hahn’s attention to the relativity of fundamental logical axioms and symbolic notation paralleled similar conventionalist discussions in geometry, especially by Poincaré.
Rational decision-making became a central issue in Neurath’s economic thinking. All the more so when Neurath noted the limitations of the calculation of collective comparative pleasure and displeasure associated with different sets of goods (Neurath 1912). It is hardly surprising then that, even before engaging in debates over the rationality of socialist economic planning, Neurath continued examining reasoning and rationality –theoretical and practical– more generally. In Vienna, the intellectual and social project was connected to the spirit of the Enlightenment. In an essay of 1913, ‘The lost wanderers of Descartes and the auxiliary motive (on the psychology of decision)’ (Neurath 1913) he criticized Descartes’ theoretical rationalism and examined his psychology of action to explore decision-making under uncertainty. He introduced a general distinction, for theoretical and practical reasoning, between rationality and pseudo-rationalism. He dismissed as pseudorationalism the ideal of replacing instinct and authority with formal reasoning and calculation as the sole and sufficient method of decision-making based on conclusions without awareness of cognitive limitations or incomplete insight.
Instead, he argued, conclusions about courses of action, including the acceptance of hypotheses, are typically in need of supplementing with additional considerations he called auxiliary motives. The recourse is justified pragmatically. In general, what counts as an auxiliary motive might be external motives, values or conventions (goals or constraints as reasons) and pure decision procedures including the drawing of lots –since making any decision is more important than any decision made– (on the pure proceduralist interpretation see Bentley 2023). This volutntarism, decisionism and pragmatism became central to his contributions to the scientific epistemology of logical empiricism. He referred then also to unavoidable extra-logical factors (Neurath 1934).
3.3 Scientific and linguistic epistemology
Kant had delivered the latest grand attempt to address the relation between science and philosophy, by taking the former to provide objective empirical knowledge (exact, universal and necessary) and giving to the latter knowledge the task of laying out the a priori conditions of intelligibility and possibility of such knowledge as the sole, critical scope of metaphysics and legitimate exercise of reason. Kant’s standard of a priori, an expression of rationality, was challenged and relativized by Frege, Russell and Whitehead’s notions of mathematical numbers grounded in logic, by models of non-Euclidean geometry and their analysis by Poincaré and by the new notions of space and time in Einstein’s relativity theories. Neither mathematics was synthetic nor physics seemed a priori; as a result, in the new scientific landscape the metaphysical category of synthetic a priori was dismissed as empty of content.
With the scientific world-conception, logical empiricists followed in the footsteps and Helmholtz and Mach and considered a new post-Kantian problematic: investigating the possibility of objective empirical knowledge with a role for intellectual construction without universality or necessity, neither Kantian apriorism nor radical positivism. Logic, with scientific status linked to technical symbolism and the possibility of mathematics, was the sole last refuge for philosophy. The new problematic suggested a demarcation project with two inseparable tasks that were both descriptive and normative: a positive, unifying task to establish and promote the marks of scientific knowledge and the negative task to distinguish it from philosophy, especially the objects and concepts of metaphysics.
According to logical empiricists a priori knowledge claims expressed in exact theory were circumscribed to the analytic. Yet they were voided of universality and necessity (Kant’s marks of the a priori) and deflated by Schlick and Reichenbach to the character of definitions and conventions (following Poincaré). They were true or valid only relatively and by construction. Synthetic knowledge claims were exclusively a posteriori, their contents and validity grounded in experience.
The philosophical discussion that developed around the members of the Vienna Circle was associated with the formulation of logical empiricism and the rallying cry of ‘unity of science against metaphysics.’But it cannot be adequately understood without taking into account the diversity of evolving projects it accommodated. Carnap’s and Neurath’s respective metascientific stance has been mentioned above. Carnap was much borrowed from the neo-Kantian tradition, Einstein’s theories of relativity, Husserl’s phenomenology, Frege’s logic and, i.e., Hilbertian axiomatic approach to mathematics as well as Russell’s own logicism and his philosophical project of logical constructions. He was concerned with the conditions of the possibility of objective knowledge, which he considered especially manifest in the formal exactness of scientific claims (Carnap 1928). Schlick borrowed from turn-of-the-century French conventionalists such as Rey, Duhem and Poincaré, Wittgenstein’s philosophy of representation of facts, as well as Einstein’s relativity theories and Hilbert’s implicit definitions and axiomatic approach to mathematics. He was interested in the meaning of terms in which actual scientific knowledge of reality is expressed, as well as its foundation on true and certain beliefs about reality (Schlick 1918, 1934). Also Reichenbach had been influenced by and borrowed from Einstein, neo-Kantianism and Hilbert’s axiomatics. Neurath borrowed, among others, fromm Mach, varieties of French conventionalism, especially Duhem’s, and varieties of social thought including Marxism. He sought to explore the empirical and historical conditions of scientific practice in both the natural and social sciences (Neurath 1931/1973, 1932a/1983). Outside the Vienna Circle, Popper borrowed from Hume, Kant and Austrian child psychology. He was interested in addressing the logical and normative issues of justification and demarcation of objective and empirical scientific knowledge, without relying on descriptive discussions of the psychology of subjective experience and meaning (Popper 1935/1951).
The linguistic turn framed the examination of the controversial role of experience and the form of its expression and relation to hypotheses. In that respect an ensuing discussions of data or so-called protocol sentences concerned their linguistic characteristics and their epistemological status (Uebel 1992). It served the Circle’s purpose of ascertaining the source, evaluation and acceptance of human knowledge and rejecting metaphysics as nonsense—often dangerous nonsense (Carnap, Hahn and Neurath 1929/1973, and Stadler 2007).
Neurath’s departing position was a critique of Carnap. In his classic work Der Logische Aufbau der Welt (1928) (known as the Aufbau and translated as The Logical Structure of the World), Carnap investigated the logical ‘construction’ (Russell’s term) of objects/concepts of inter-subjective knowledge out of the simplest starting point or basic types. To reconstruct empirical knowledge, Carnap explored an empiricist, or phenomenological, model in terms of the immediate experiential basis was quickly understood by fellow members of the Vienna Circle as manifesting three philosophical positions that structured the debate: reductionism, atomism and foundationalism.
Reductionism took one set of terms to be fundamental or primitive; the rest would be logically connected to them.
Atomism, especially in Neurath’s reading, was manifest semantically and syntactically: semantically, in the analyzability of a term; syntactically or structurally, in the elementary structure of protocols in terms of a single experiential term—‘red circle here now.’ It appeared further in the possibility of an individual testing relation of a theoretical statement to one of more experiential statements.
Foundationalism, in the Cartesian tradition of a secure basis, took the beliefs in these terms held by the subject to be infallible, or not requiring verification, and the sole empirical source of epistemic warrant—or credibility—for all other beliefs. Descartes’s foundationalism is based on a priori knowledge; Carnap’s presentation of the empirical basis constitutes a more modest, naturalistic version (see also his 1932/1987).
Neurath first confronted Carnap on yet another alleged feature of his system, namely, subjectivism. On this issue dovetailed Carnaps’ Kantian problematic of explicating the objectivity of empirical knowledge and Neurath’s materialism and social –and socialist– perspective on economic, political and epistemic matters. Neurath rejected Carnap’s proposals on the grounds that if the language and the system of statements that constitute scientific knowledge are intersubjective, then phenomenalist talk of immediate subjective, private experiences should have no place. More generally, Neurath offered a private language argument, featuring Robinson Crusoe, to the effect that languages are necessarily intersubjective:
The universal jargon…is the same for the child and for the adult. It is the same for a Robinson Crusoe as for a human society. If Robinson wants to join what is in a protocol of yesterday with what is in his protocol today, that is, if he wants to make use of language at all, he must make use of the ‘intersubjective’ language. The Robinson of yesterday and the Robinson of today stand precisely in the same relation in which Robinson stands to Friday…In other words, every language as such is intersubjective. (Neurath 1932b/1983, 96)
To replace Carnap’s phenomenalist language Neurath introduced in 1931 the language of physicalism (Neurath 1931/1983 and 1932a/1983). Physicalism is, for Neurath, the view that the unity, intelligibility and objectivity of science rest on using statements in a language of public things, events and processes in space and time —including behavior and physiological events, hence not necessarily in the technical terms of physical theory. Carnap promptly adopted a more technical version of physicalism requiring translatability of protocols to the language of physics (Carnap 1932/1934). While inspired by anti-metaphysical materialism, for Neurath this was a methodological and linguistic rule, and not an ontological thesis. The syntacticism mentioned above concerns the emphasis on spatio-temporal order or patterns. Neurath’s view could claim that language was itself was a physical process and could express its own spatio-temporal structure. This was also in line with his typographic concerns in logic and visual communication.
That physicalism was to avoid metaphysical connotations can be seen further in that its linguistic nature was also central to its applications. Neurath insisted that statements can be compared only with statements, certainly not with some “reality”, nor with “things,” (Neurath 1931/1983, 53). Knowledge was a social matter of empirical control.
Neurath responded with a new doctrine of protocol statements that considered their distinctive linguistic form, contents and methodological status (Neurath 1932b/1983). This doctrine was meant to explicate the idea of scientific evidence in the framework of empiricism, and it did so by specifying public conditions of evaluation and acceptance of a statement as empirical scientific evidence. In particular, Neurath intended the physicalist doctrine of protocol statements to circumvent the pitfalls of subjectivism, atomism, reductionism and foundationalism attributed to Carnap’s earlier discussion. It supported, instead, a holistic, anti-foundationalist, decisionistic, pragmatist, social view characterizing the scientific, empiricist attitude.
One informal but paradigmatic example of a protocol was:
Otto’s protocol at 3:17 o’clock: [Otto’s speech-thinking at 3:16 was: (at 3:15 o’clock there was a table in the room perceived by Otto)].
Neurath offered examples over time featuring different numbers of parts, between two and four (on the debate around this issue, see Uebel 2007). Far from Carnap’s atomic sort of protocol statements, Neurath’s model manifested a distinctive complexity of terms and structure. The protocol contains a factual physicalist core in terms about the table and its location. It also contains the experiential term that provides the linguistic recording of the empirical character of protocols, that is, their experiential origin. Neurath was mindful to caution here that perception terms only admitted physicalistic meaning in terms, for instance, of behavior or physiological mechanisms of perception. It also contains the declarative level, marked with ‘Otto says’, which distinguishes the protocol as a linguistic statement. Finally, the other distinctive elements were the name of the protocolist and the times and locations of the experience and the reports, which provided an intersubjective, physicalist, public alternative to Carnap’s first-person, subjective ‘I see a red circle here now’.
Unlike Carnap’s ideal of basic statement, whether protocol or physicalist, Neurath’s protocols were not ‘clean’, precise or pure in their terms. For Neurath physicalist language, and hence science in turn, is inseparable from ordinary language of any time and place. In particular, it is muddled with imprecise, unanalyzed, cluster-like terms (Ballungen) that appear especially in the protocols: the name of the protocolist, ‘seeing’, ‘microscope’, etc. They were often to be further analyzed into more precise terms or mathematical co-ordinations, but they often would not be eliminated. Even the empirical character of protocol statements could not be pure and primitive, as physicalism allowed the introduction of theoretical—non-perception—terms. Physicalism, and thus unified science, were based on a universal ‘jargon’.
Neurath’s protocols didn’t have the atomic structure and the atomic testing role of Carnap’s. Their methodological role reflected Duhem’s holism: hypotheses are not tested individually; only clusters of statements confront empirical data. But their methodological value in the testing of other statements didn’t make them unrevisable. This is Neurath’s anti-foundationalism: Insofar as they were genuinely scientific statements, consistency with the spirit that opposed science to dogmatic speculation and, no less importantly, opposed naturalistic attention to actual practice, required that protocols too be testable. Physicalism challenges the epistemic authority of first-person private experience and enables the democratic socialization of empirical claims in the networks of scientific statements and collaborations.
From this follows the so-called Neurath Principle: in the face of conflict between a protocol and theoretical statements, the cancellation of a protocol statement is a methodological possibility as well (Neurath 1932b/1983, Haller 1982). The role of indeterminacy in the protocol language points to a distinction between a special Neurath Principle and a general Neurath Principle (Cartwright et al. 1996, Cat 1995). In the former, and earlier, Neurath assumed a determinate logical relation of inconsistency. In the latter, subsequent version, the scope of relations between hypotheses and protocol statements extended to indeterminate relations such that the principle behind the epistemic status of protocol statements is simply grounded on the voluntaristic and conventionalist doctrine that ‘[a]ll content statements of science, and also their protocol statements that are used for verification, are selected on the basis of decisions and can be altered in principle’ (Neurath 1934/1983, 102).
The complex structure of the explicitly laid out protocol would provide an explication and synoptic visual tool for differentiating and integrating explicitly relevant testing conditions: the intersubjective conditions of evaluation and acceptance of the record and its core data, or record of core factual information to enter the relevant scientific field of empirical research. The different conditions could guide the control of relevant data by laying out the conditions of their origin, validity and fallibility (was Otto hallucinating? were all the parts of the experimental instrument working reliably? etc.).
Neurath’s dictum was meant to do justice to actual scientific practice and its normative standards with regards to the role of experimental data. It is up to the members of the scientific community to decide when a protocol can support or challenge a hypothesis, at last provisionally. Invalid protocols may change their status or be repurposed as data for historical or social studies of science (Uebel 2007 and Bentley 2023). What distinguishes the epistemic status of protocol sentences is not their foundational certainty (unlike for Schlick), but their stability as available and acceptable records over time and across projects and purposes. In this way they facilitate communication, cooperation and empirical inquiry.
The method of testing failed to meet a certain standard and expectation of rationality: It could not be carried out in a logically precise, determinate and conclusive manner. expecting calculability, determinism, omniscience and certainty (Neurath 1913/1983, Neurath 1934/1983 and Cat 1995). By virtue of perception terms, protocol sentences could in fact provide certain stability in the permanence of information necessary for the generation of new expressions. But methodologically they could only bolster or shake our confidence. To acknowledge these limitations is a mark of proper rationality—which he opposed to pseudorationality.
A loose coherentist view of warrant, acceptance and unification is the only logical criterion available: ‘a statement is called correct if it can be incorporated in this totality’ of ‘existing statements that have already been harmonized with each other’ (Neurath 1931/1984, 66). Reasons underdetermine our actions and thus pragmatic extra-logical factors are required to make decisions about what hypotheses to accept. Thinking requires provisional rules, or auxiliary motives, that fix a conclusion by decision (Neurath 1913/1983).
Scientific rationality is situated, contextually constrained by, practical rationality. The construction of knowledge is constrained by historically, socially, methodologically and theoretically accepted claims and standards –as well as other possible factors he called extra-logical. They bear limited stability, and cannot be rebuilt on pure, secure, infallible empirical foundations. This is the anti-Cartesian naturalism, non-foundationalism, fallibilism and holism of Neurath’s social model. This is also the basis for its corresponding decisonistic, conventionalist, constructivist normativity (Uebel 1996 and 2007 and Cartwright et al. 1996). Without the norms and conventions self-issued within a community, there is no possibility of rationality or objectivity of knowledge. Neurath captured the main features of his doctrine of scientific knowledge in the image of a boat:
There is no way to establish fully secured, neat protocol statements as starting points of the sciences. There is no tabula rasa. 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 its best components. Only metaphysics can disappear without a trace. Imprecise ‘verbal clusters’ [Ballungen] are somehow always part of the ship. If imprecision is diminished at one place, it may well re-appear at another place to a stronger degree. (Neurath 1932b/1983, 92)
Just like Neurath debated Carnap, he also entered an acrimonious debate with Popper and Schlick. By 1934, the year of the completion of his Logic of Scientific Discovery (Logik der Forschung), Popper had adopted an approach to scientific knowledge based on the logic of method, not on meaning, so that any talk of individual experience would have no linguistic expression(Popper 1935/1951). He was concerned with the post-Kantian problematic of the rational objective validity of scientific knowledge claims.
Instead of protocols, Popper proposed to speak about basic statements—a term more attuned to their logical and functional role. They are basic relative to a theory under test. Their empirical character would invisibly reside in the requirement that basic statements be singular existential ones describing material objects in space and time—much like Neurath’s physicalism—which would be observable, in a further unspecified logical not psychological sense. Their components would not themselves be purely empirical terms since many would be understood in terms of dispositional properties, which, in turn, involved reference to law-like generalizations. But their ‘basic’ role was methodological ‘with no direct function of demarcation from metaphysics in terms of meaning, sense or cognitive significance’ and only provisional. They would be brought to methodological use for the purpose of falsifying theories and hypotheses ‘individually and conclusively’ only once they were conventionally and communally accepted by decision in order to stop infinite regress and further theoretical research.
But such acceptance, much as in Neurath’s model, could be in principle revoked. It is a contingent fact that scientists will stop at easily testable statements simply because it will be easier to reach an agreement. It is important that basic statements satisfy explicit conditions of testability or else they could not be rightful part of science. Popper could offer no rational theory of their acceptance on pain of having to have recourse to theories of psychology of perception and thereby weakening his normative criterion of demarcation. In his view, his method, unlike Neurath’s, didn’t lead to either arbitrariness or dogmatism or the abandonment of empiricism. As he had argued against Spengler in 1921, historical contingency provides the rich constraints that establish communities and communication and the possibility of knowledge and, in this holistic form, preclude radical relativism in practice; in historically situated practice, inherited or constructed stable Archimedean points always come into place; there is no tabula rasa (Neurath 1921/1973). Neurath rejected Popper’s approach for its stealth empiricism and its pseudorationalism: its misplaced emphasis on and faith in the normative uniqueness, precision and conclusiveness of a logical method—at the expense of its own limitations and pragmatic character (Zolo 1989, Cat 1995, Hacohen 2000).
Finally, the most radical empiricist attitude toward protocol sentences within the Vienna Circle came from Schlick. Schlick endorsed, following Hilbert, a formal, structural notion of communicable, objective knowledge and meaning as well as a correspondence theory of truth. His realism opposed Neurath’s coherentism, and also the pragmatism and conventionalism of Carnap’s Principle of Tolerance in logical matters, as well as his Thesis of Metalogic. But like Carnap’s latter thesis and his syntactic approach of 1934, Schlick was concerned with both the Cartesian ideal of foundational certainty and Wittgenstein’s metalinguistic problem of how language represents the reality it is about; such relation could only be shown, not said. In 1934 Schlick proposed to treat the claims motivating protocol statements, left by Neurath with the status of little more than mere hypotheses, as key to the foundation of knowledge. They would be physicalistic statements that, albeit being fallible, could be subjectively linked to statements about immediate private experiences of reality such as ‘blue here now’ he called affirmations (Konstatierungen) (Schlick 1934).
Affirmations carried certainty and elucidated what could be showed but not said, they provided the elusive confrontation or correspondence between theoretical propositions and facts of reality. In this sense they afforded, according to Schlick, the fixed starting points and foundation of all knowledge. But the foundation raised a psychological and semantic problem about the longer-term acceptance of a protocol. Affirmations, as acts of verification or giving meaning, lacked logical inferential force; in Schlick’s words, they ‘do not occur within science itself, and can neither be derived from scientific propositions, nor the latter from them’ (Schlick 1934, 95). Schlick’s empiricism regarding the role of protocol sentences suggests but does not support strong epistemological foundationalism. Schlick’s occasional references to a correspondence theory of truth were just as unacceptable and were felt to be even more of a philosophical betrayal within the framework of empiricism. Predictably, Neurath rejected Schlick’s doctrines as metaphysical, manifesting the pseudorationalist attitude (Neurath 1934/1983).
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