Abstract
Carnap’s work was instrumental to the liberalization of empiricism in the 1930s that transformed the logical positivism of the Vienna Circle to what came to be known as logical empiricism. A central feature of this liberalization was the deployment of the Principle of Tolerance, originally introduced in logic, but now invoked in an epistemological context in “Testability and Meaning” (Carnap 1936a, 1937b). Immediately afterwards, starting with Foundations of Logic and Mathematics, Carnap (1939) embraced semantics and turned to interpretation to guide the choice of a theoretical language for science. The first thesis of this paper is that recourse to an intended interpretation led to a partial retrenchment of the conventionalism implied by the Principle of Tolerance. It required that the choice of a language be based on abstraction from a (typically empirical) context; this procedure later became a component of the process of explication that was distinctive to Carnap’s mature views. The (typically empirical) interpretive origin of formal systems also ensured their likely syntactic consistency, an issue on which Carnap was strongly criticized by figures such as Beth and Gödel. The second thesis of this paper is that this reliance on an intended interpretation enabled constructed formal systems to be relevant to the development of empirical science.
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Notes
For once-popular dismissive attitudes to logical empiricism, see, for example, the contributions in Suppe (1977b).
The locution “liberalization of empiricism” is due to Carnap (1963a, §9) and it referred to the developments initiated in “Testability and Meaning.” The sense in which TM went even beyond the Principle of Tolerance was in the suggestion that empiricism itself was to be taken as a proposal—see Section 4, below.
Whether logical empiricism should—or can—be usefully distinguished from logical positivism is itself a matter of controversy; if the two programs can be usefully distinguished, how this should be done is a matter of even further controversy. For instance, Creath (2011) and Uebel (2011) deny that there is any distinction of relevance. For Leitgeb (2011), the distinction is that which marked the Vienna Circle’s transition from empiricism to the philosophy of science—this is consistent with the central role for “Testability and Meaning” that is being urged in this paper. On Salmon’s (1999) construal, Reichenbach’s (1938) Experience and Prediction, which treated the same subjects as Carnap (1936a, 1937) though from Reichenbach’s very different probabilistic perspective, was the first major work of logical empiricism. While the origin of the term “logical empiricism” remains uncertain (see below), in the sense that is relevant to the discussions of this paper it goes back at least to Neurath (1931, 1935) who advocated physicalism over phenomenalism and the liberalized perspective towards empiricism. The First Congress for the Unity of Science in Paris, 1935 began with a session “Philosophie scientifique et empiricisme logique,” presumably because of Neurath’s role in its organization (Stadler 2001, p. 366). See, also, Kaila (1936) who was at times a peripheral member of the Vienna Circle. Meanwhile, Reichenbach (1936) introduced the awkward “logistic empiricism.” Uebel (2013) discusses earlier uses of “logical empiricism” in somewhat different, though not entirely unrelated, senses—for instance, by Kaila in 1926 and Dewey as early as 1907. In any case, the question whether logical empiricism should be distinguished from logical positivism is marginal to the issues that are central to this paper which are (i) the conventionalist implications of the Principle of Tolerance for empiricism, (ii) the partial retreat from a radical empiricism through the acceptance of formal semantics, and (iii) the role of interpretation in Carnap’s account of formal systems.
As noted earlier, at least some recent work does treat TM—see, e.g., Creath (1992), Psillos (1999), and Demopoulos (2007) but it deserves more attention than that. Interestingly, TM did receive attention in earlier work in philosophy of science, even those that reject rather than develop logical empiricism, e.g., Suppe (1977a). In contrast FLM appears to have been relatively ignored; Beth (1963), which will briefly be discussed in the text below (Section 6), is perhaps the most notable early exception. Koellner (2009) provides a brief but important treatment which will also be considered later in this paper.
The term “logical positivism” was apparently introduced by Blumberg and Feigl (1931).
Details throughout this section are from Sarkar (1992).
It was published in two parts in 1936 and 1937 (Carnap 1936a, 1937b). The date of composition is partly based on which works Carnap (1937b) identified as having been written after the composition of TM. These included Neurath (1935) and Ayer (1936). Some of the ideas, especially the critical move to reduction sentences, go back to one of Carnap’s contribution to the 1935 Paris First Congress for the Unity of Science (Carnap 1936b)—see, also, Uebel (2007). Thanks are due to Uebel for help with the relevant history.
See, for example, Wagner (2009).
This was a view often expressed by Burton Dreben (personal communication) who regarded Logical Syntax of Language as Carnap’s most important work. A very positive contemporary assessment is to be found in Quine’s 1934 lectures on the book which were eventually published by Creath (1990).
Note, though, that contemporary reviewers in the 1930s, particularly logicians and mathematicians, did not find the move particularly surprising or interesting—see the discussion of these reviews in Sarkar (1992): entrenchment of a single system (or even a small set of systems) as “logic,” as later happened in much of analytic philosophy, is notably absent.
What Carnap had in mind was the system of Principia Mathematica but that makes the second claim problematic. At the conference at which Carnap made that claim (in a symposium in which Heyting and von Neumann presented the intuitionist and formalist positions, respectively), Gödel announced his first incompleteness result as part of the ensuing discussion (Sarkar 1992). But even without that, the Axioms of Infinity and Reducibility (which were part of the system of the Principia) were problematic insofar as it was far from clear that they counted as legitimate logical axioms.
For the earlier use of this argument in 1931, see Dawson (1984). At that point, given the characterization of logicism (in the text above), this argument for logicism was only of subsidiary importance. With the Principle of Tolerance, it became central to any defense of logicism over formalism (Sarkar 1992).
Tarski (1935) is listed as one of the works that was published only after TM was composed which may explain why its methods were not deployed at this stage (compared to FLM).
However, Carnap does not use the term “logical empiricism,” preferring “scientific empiricism” instead (Carnap 1937b, p. 38).
Indeed, this is what Carnap (1963a, §9) primarily had in mind in referring to these developments as the liberalization of empiricism.
For a full discussion see Carnap (1936a), pp. 422–424.
Additionally, as part of the ongoing liberalization of empiricism, Carnap no longer prioritized the methodological solipsism of Logische Aufbau der Welt which had found much but not complete support within the Vienna Circle; this avoidance was motivated by the situation that “in spite of all explanations and warnings [methodological solipsism] . . . was often misunderstood” (Carnap 1936a, p. 424). The same point also pertains to the use of an autopsychological basis for the construction of the world in that work.
Demopoulos (2007) takes this aspect of the liberalization of empiricism to be central to TM and concludes that TM “is the clearest anticipation of the mature view [on rational reconstruction of theories that Carnap] developed in the 1950s and 1960s” (p. 249). In contrast, the present paper views TM as constituting the final stage of Carnap’s syntacticism and sees more continuity between it and previous works such as Logical Syntax of Language, than between it and works that accept semantics and emphasize interpretation, starting with FLM. Nevertheless, the point that explicit definitions may not be possible for all theoretical concepts in science is an important development in Carnap’s epistemological views during this period.
This is why Sarkar (1992) argued that Logical Syntax of Language should be judged on the basis of what it contributed to technical logic and the foundations of mathematics rather than it advocacy of particular philosophical positions.
There were many editions of FLM, identical in content, but with different pagination because the piece was both issued independently and as part of volumes of the different editions of the International Encyclopedia of Unified Science. Citations, therefore, include section numbers which were cumulative even though the work was divided into three chapters; page numbers are to the Carnap (1939) edition.
Carnap gave an example: “Suppose that we have found that the word ‘mond’ of B was used in 98 % of the cases for the moon and 2 % for a certain lantern. Now it is a matter of our decision whether we construct the rules in such a way that both the moon and the lantern are designata of ‘mond’ or only the moon. If we choose the first, the use of ‘mond’ in those 2 % of cases was right—with respect to our rules; if we choose the second, it was wrong” (FLM, § 4, p. 6).
Koellner (2009) emphasizes this role of choice. However, in contrast to the arguments being presented here, he ignores the issues of abstraction and interpretation which results thereby in his also ignoring the role of empirical science in Carnap’s project.
“Titisee” is supposed to be the name of a lake in a fictitious country; on certain holidays the lake happens to be called “rumber” (FLM, § 3, p. 5).
However, this is not a return to Carnap (1931) where he says: “Logicism proposed to construct the logical-mathematical system in such a way that . . . that the axioms are chosen with an interpretation of the primitive symbols in mind” which left virtually no discretion at all.
This is how Carnap (1963b, p. 902, italics as in the original) puts it: “To give an interpretation for a language (or for an axiom system) is to assign meanings to the signs and sentences, either formally by explicit semantical rules or informally by non-technical indications of any form. An interpretation should not be identified with a model, as is sometimes done. It is true that an interpretation can sometimes be given by the specification of a model. But there is no one-to-one correspondence between interpretations and models; two different (i.e., not logically equivalent) descriptions of the same model represent two different interpretations.”
For a different analysis of Carnap’s response, see Awodey and Carus (2007).
Note that explication is the abstraction1 to the semantic rules from the pragmatic context; it is not the abstraction2 of the syntactic rules from the semantic ones which is also part of the contextual procedure or language construction in FLM.
See § 6, “Formalization and Interpretation,” of Chapter 1 of Carnap (1950).
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For comments on an earlier draft and discussions, thanks are due to Veronika Hofer, Cory Juhl, Anya Plutynski, Michael Stöltzner and, especially, Thomas Uebel. This paper has also benefited from very useful criticism from two anonymous referees for this journal.
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Sarkar, S. Carnap and the compulsions of interpretation: Reining in the liberalization of empiricism. Euro Jnl Phil Sci 3, 353–372 (2013). https://doi.org/10.1007/s13194-013-0073-2
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DOI: https://doi.org/10.1007/s13194-013-0073-2