Online research in philosophy

A variant of the standard deductive tableau system is introduced, and interrogative rules are added, resulting in a so-called interrogative tableau system. A game-theoretical account of entailment is sketched, and the deductive tableau system is interpreted in these terms. Finally, it is shown how to extend this account of entailment into an account of interrogative entailment, thereby providing a semantics for the interrogative tableau system.

In Jaakko Hintikka's interrogative model of inquiry, the strategic principles governing empirical inquiry (interrogatively construed) turn out to be closely related to those governing deductive reasoning. Hence it is important to study the precise analogies which obtain between deductive logic and interrogative inquiry. The basic concept of the interrogative model is the relation of model consequence $\text{M}\colon \text{T}\vdash \text{C}$ . It is said to obtain iff C can be derived from T by means of an interrogative process in the model (...) M (in the logicians' sense of model). We prove here a counterpart of Craig's interpolation theorem for the concept of model consequence. The interrogative analogue to definability is a logical generalization of methodologists' concept of identifiability. For this concept, we prove an analogue to Beth's theorem. Some further philosophical consequences of these results are mentioned. For instance, identifiability is a good rational reconstruction of the idea of observability (measurability). (shrink)