Carnap’s conception of language was deeply influenced by Frege. In 1910 and 1913 he attended Frege’s courses on Conceptual notation (Begriffsschrift), and later studied Frege’s other works. Carnap followed Frege in wanting to devise a purified logical language to be used as a sharp analytical tool. But whereas Frege’s main concern was with the foundations of mathematics (although his reflections on language are by no means restricted to the language of mathematics), Carnap would soon understand the significance of such an instrument for the analysis of philosophical problems and work on the possibility of its application to the propositions of science in general. Before 1931, however, Carnap did not articulate any systematic theory of language. Language was to be used as a universal notation, but not regarded as an object of study in its own right. In The Logical Structure of the World (1928), for example, no systematic account of what a language is, or method of studying lan-guages, was provided. Indeed, Carnap and other members of the Vienna Circle were deeply influenced by Wittgenstein’s claim that the form of a proposition, as well as many other properties of language and linguistic expressions, cannot be meaningfully stated, although they can be shown (Wittgenstein, 1921/1922, §§4.121, 4.1212, 6.36), and for some time they were not even sure that it was possible to talk about language – to describe its syntax, for example – in a meaningful way.
Things changed radically in the early 1930s: Carnap rejected Witt-genstein’s assessment of any metalinguistic discourse as meaningless, and he decided to apply the distinction between an object-language and a metalanguage to the analysis of the language of science as a whole. The idea was to distinguish between a language regarded as an object of study (the ‘object language’) and a (possibly different) lan-guage in which the study itself was conducted (the ‘metalanlan-guage’).1 Three authors had been instrumental in this methodological turn. First, in the 1920s, Hilbert had introduced the method of metamathematics, in which the sentences and proofs of mathematics were first codified in a formally defined language and then taken as an object of study in their own right. This was one of the basic ideas of Hilbert’s programme, which aimed at proving (meta)mathematically some properties (com-pleteness, consistence, decidability etc.) of mathematical (formalized) theories. Secondly, Carnap had learned from Tarski about the use of
metalogic in the Polish school of logic: taking a metalinguistic viewpoint in order to formulate statements and give logical proofs about logic.
Thirdly, as early as 1930, Carnap heard of Gödel’s method for the arith-metization of syntax. This offered a clear way of expressing statements about some language L in L itself. The idea of a metalinguistic method suitable not only for logic or mathematics but for the whole language of science occurred to Carnap in 1931, while he was working both on the foundations of mathematics and on the reconstruction of the system of our knowledge. Carnap relates this event in a colourful passage of his
‘Intellectual Autobiography’:
After thinking about these problems for several years, the whole theory of lan-guage structure and its possible applications in philosophy came to me like a vision during a sleepless night in January 1931, when I was ill. On the following day, still in bed with a fever, I wrote down my ideas on forty-four pages under the title ‘Attempt at a metalogic’. These shorthand notes were the first version of my book Logical Syntax of Language. (Carnap, 1963a, p. 53)
The Logical Syntax of Language was published in 1934 in German, and an augmented version was translated into English and published in 1937.
It contains Carnap’s first systematic exposition of a method for studying languages, what he called the syntactical method. This excluded any use of the concepts of meaning, reference and truth. Shortly after the publi-cation of the German edition, however, Carnap heard from Tarski about his method for providing exact definitions of truth for deductive lan-guage systems. He acknowledged that Tarski’s semantic metalanlan-guage offered an important and precise way of explicating many logical con-cepts (such as logical consequence, or logical truth) and he soon comple-mented his syntactical method with a semantic one. In the late 1930s, he also borrowed distinctions from Charles Morris, dividing the theory of language into syntax, semantics and pragmatics (Carnap, 1939). Whereas syntax restricts its investigations to the formal properties of expressions and the formal relations between them, semantics (at least as it is envis-aged by Carnap) takes into consideration the relationships between the expressions of a language and their designata (i.e. what they stand for or refer to). As for pragmatics, it considers also the speaker and her linguis-tic activities, not only the expressions themselves and their designata.
With hindsight, the restriction of any metalinguistic talk about language to syntactical properties of linguistic entities and syntactical relations
between them may be interpreted as an overreaction to the difficulties raised by various semantic paradoxes and theories of meaning.2
With the introduction of the syntactical method, Carnap thus makes two different moves – moves intertwined in Logical Syntax, but clearly distinguished in later works, after his acceptance of semantics. The first move is the adoption of a metalinguistic viewpoint for the study of lan-guages which are then taken as objects of study. Against some of Wit-tgenstein’s claims in the Tractatus, and in particular his contention that there are no (meaningful) sentences about the form of sentences, Car-nap maintains that we should stop talking about Language, as if there were just one logical structure common to all languages, and consider instead the possibility of defining varieties of languages.3 In addition, Carnap shows that there is a correct and acceptable way of formulating sentences about the sentences of a language. The second move consists in restricting the method used in the metalanguage to a syntactical one, excluding any talk about correspondences between linguistic expres-sions and objects of the world, and any consideration of meaning or reference.
The ‘vision’ Carnap had during the sleepless night of January 1931 brought a new conception of language, to which we shall return below;
but this ‘vision’ also includes a new approach to philosophical problems through language. In the foreword to Logical Syntax, Carnap articulates a new understanding of the relationships between science, philosophy and the logical analysis of language:
Philosophy is to be replaced by the logic of science – that is to say by the logical analysis of the concepts and sentences of the sciences, for the logic of science is nothing other than the logical syntax of the language of science. (Carnap, 1934/1937, p. xiii)
In a sense, logical analysis had already been applied to the concepts and sentences of the sciences in The Logical Structure of the World of 1928.
What is new in 1931 is the recognition that many philosophical problems result from a lack of clear distinction between object-questions, which concern some specific domain of objects, and logical questions, which are about terms, sentences and other linguistic elements which refer to objects. According to Carnap, traditional philosophy tends to treat what are actually logical questions as if they were object-questions, thus making use of what Carnap calls the ‘material mode of speech’; and
consequently traditional philosophers can be (and often were) misled into thinking they are talking about things, when the problems they are trying to solve should really be thought of as problems about language (Carnap, 1934/1937, §72). In order to get rid of the pseudo-problems which result from this confusion, philosophy is to be replaced by the logical analysis of the language of science. This is Carnap’s version of the so-called linguistic turn, taken by him in the early 1930s when he distin-guished object-languages from metalanguages, and object-questions from logical ones. This is the basis of Carnap’s ontological deflationism, which he often illustrates with the case of numbers. Asking about the
‘essence of numbers’ in an absolute way amounts to posing a typical pseudo-problem. The ‘essence’ question simply overlooks the relativity of number-talk to language: a formulation such as ‘5 is a number’ (typical of the material mode of speech) is misleading and should be replaced by
‘“5” is a number-sign in language L’ (which amounts to a translation of the former sentence into what Carnap calls the ‘formal mode of speech’).
Consequently, instead of asking about the ‘essence’ of numbers, what numbers ‘really are’, Carnap suggests that philosophers discuss and make decisions about the kind of number-signs which it would be most convenient to introduce (for some particular purpose) in the language we want to use. Another significant consequence of Carnap’s view is that philosophical theses lose the absolutist character they have in trad-itional philosophy and are then relativized to some language – for example, one should not try to talk about the unity of science without mentioning the language in which this unity is supposed to be realized (see, for example, Carnap, 1935a/1996, p. 78).4
Although the linguistic turn was taken at the time Carnap advocated a purely syntactical method, he never renounced the linguistic turn itself, even when he embraced semantics. For him, language analysis remained
‘the most important tool in philosophy’ (Carnap, 1963a, p. 60).