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The picture of theories provided by the received view is tightly bound to experience and the world. This occurs because the logical empiricists held the view that for the theoretical language of a scientific theory to be meaningful, to have cognitive significance, it had to be grounded in experience of phenomena. Accordingly, there are not separate views of theories and data; rather, the view of theories and data has the two inseparably entangled together. All cognitively significant discourse about the world was required to be empirically verifiable, at least in principle. Accordingly, all assertions of a theory were required to be reducible, at least partially, to assertions about phenomena in an observation or protocol language. This reduced the problem of how theoretical statements are verified to that of determining how observation or protocol assertions were to be verified.

There was initially debate about the terms in which observational experiences could be described such that observational or protocol sentences were clearly true or false in a particular experiential context. Some members of the Vienna Circle preferred a phenomenalistic language, specified in terms of a sense-datum language. These would be immune to any concerns about truth or falsity, since it was believed that sense-datum descriptions of one’s phenomenal experience could be known with absolute certainty. Others preferred a physicalistic language, a language describ-

ing the observable properties of material things. Since the observation or protocol language would refer only to observable properties, assertions about experience of phenomena would be intersubjective, and for verifiable propositions it would be en- tirely clear whether or not a given thing had the property asserted of it. Physicalistic language won out in the end, causing the received view to endorse materialist meta- physics, even though the content of all assertions was grounded in observation.

Following the formulation in the classic account given by Suppe (1974), the re- ceived view takes a theory to be formulated in a first order language L, which has an associated logical calculusK , specifying the laws of classical valid inference. The language L could be augmented by modal operators in order to support the use of counterfactuals. The language L is then required to have a specific substruc- ture. The nonlogical primitive constants, or terms, ofL are divided into two disjoint classes: the nonempty observation vocabulary VO and the theoretical vocabulary VT. The language L is then divided into three sublanguages, each of which having an associated subcalculus, the restriction of K to the given sublanguage:

(i) Theobservation language,L_O, which contains no quantifiers or modal operators, contains all the observational vocabulary VO and none of the theoretical vocab- ularyVT. LO is the language used to formulate assertions of direct phenomenal experience.

(ii) The logically extended observation language,L_O′, an extension of L_O to include quantifiers and modal operators, etc., of L. This language is used to formu- late generalizations about experience and supports the use of counterfactual statements about experience.

(iii) The theoretical language,L_T, the sublanguage ofL that contains noVO terms.

LT is used to formulate the theory or theoretical framework, independently of

its interpretation in experience.

These sublanguages do not exhaustL because it also containsmixed sentences, which contain at least one term from each of VO and VT. This sort of sentence is necessary to give the theory an interpretation in experience.

It remains then to give the language L an interpretation. Given the crucial role of the observation language in giving theoretical content meaning, L_O must be

given a semantic interpretation in a domain of concrete observable events, where the obtaining of properties and relations is directly observable. This can then be extended to an interpretation of L_O′ for empirical generalizations and counterfactual claims. This provides a partial interpretation of the observational part of L. The partial interpretation of the theoretical terms and L-sentences containing them is given by the following two kinds of postulates:

(i) The theoretical postulates T, the axioms of the theory, containing the terms of

VT; and

(ii) The correspondence rules C, which are mixed sentences that contain at least one term from each of VO and VT. These rules provide a partial interpretation of the theoretical part of L by grounding it in the semantic interpretation of the observation language.

Letting T and C designate the conjunctions of the theoretical postulates and corre- spondence rules, respectively, the scientific theory based on L, T and C, is denoted

T C. The theory may alternatively be represented as the set of sentences T formed by the deductive closure K (T C)of the postulates T C.

Although the form and function of correspondence rules changed during the devel- opment of the received view, throughout they function to specify which experimental procedures are admissible for applying a theory to phenomena. The role of the corre- spondence rules, ultimately, was to specify sufficient conditions for the statements of the theory to be empirically meaningful. This provides clear criteria for determining the observable consequences of the theory that make it testable, and in the process provides a partial interpretation of the termsVT by specifying their observational con- tent. Terms are partially defined rather than fully defined because the correspondence rules only place conditions on admissible experimental procedures for application to observable phenomena, rather than giving a set of necessary and jointly sufficient conditions in terms of observable phenomena. The latter cannot, in general, be done without making particular measurement devices part of the empirical meaning of the theory, which would mean the theory would change with a change in instrumenta- tion. Moreover, the observable consequences are often understood to be the empirical manifestation the interaction of theoretical entities according to the axioms or laws of

the theory (Suppe,1974, 25). Consequently, theoretical terms cannot then be defined purely in terms of observational phenomena.

The most basic assumption on any syntactic view of theories is that the logical structure of scientific language is to be elucidated through its reconstruction in a

language in formal logic, usually first order logic. This leaves the manner in which a semantics is specified for that language open. The received view handled this by using correspondence rules to ground meaning in experience. Since Tarski’s work in model theory had a profound effect on both logic and philosophy of science, the semantics of a theory is now generally provided not by interpretation in experience, but rather by sets ofstructures in the universeVof sets. A formaltheoretical semantics of this kind provides no means of discussing the empirical content of a theory or the manner in which it is confirmed or disconfirmed. Consequently a second empirical semantics is required to relate the theory to experience and the world. This is now most commonly understood in terms of a relation between the set-theoretic semantics of the theory and some empirical semantics. Generally, since Suppes (1962, 1969), this is understood in terms of a hierarchy of successively less general frameworks of models, down from general scientific theories to models of data and experiment. This then raises issues of the nature of the relation between set-theoretic structures and the world, which can be treated in an empiricist manner, as van Fraassen (2010) advocates, or in a realist manner, as advocated by Da Costa & French (2003), French & Ladyman

(2011), and others. This two-stage semantics, an internaltheoretical semantics in the universe of sets and an external empirical semantics in data or phenomena, is how semantic approaches to theories generally specify the theory-world relation. A purely syntactic approach, in the sense of a representation of a theory as a logical language, however, must provide an empirical semantics by relating the language of the theory to experience and perhaps also the world, which is precisely how the received view proceeds.

With the observational consequences of the theory specified, it is then possible to specify adequacy conditions for the theory. The observational adequacy2 _{of the}

2_{I take this term fromMuller(2011), which is distinguished from the concept ofempirical ade-}

quacyfrom van Fraassen’s constructive empiricism. According to van Fraassen’s definition, a “theory is empirically adequate if it has some model such that all appearances are isomorphic to empirical substructures of that model” (van Fraassen,1980, 64). In distinction to this definition, the concept ofobservational adequacydepends on the distinction between theoretical and observational concepts,

theory is then defined in terms of the set of empirically verified observational sentences

Ot(T), which grows in time t. If Ot(T) is included in the set T of sentences of the theory, then the theory is confirmed. Confirmation grows as the set Ot(T) grows while still being contained in T, and T is falsified if Ot(T) contains a sentence not inT. Muller (2011) calls this the Formal-Linguistic View.