Intensional Logic and the Irreducible Contrast between de dicto and de re

The paper deals with hot problems of current semantics that are interconnected with a fundamental question What is the meaning of a natural language expression? Our explication of the meaning is based on the key notion of Tichy’s Transparent Intensional Logic (TIL), namely that of the logical construction, an entity structured from the ‘algorithmic point of view’ (procedure), the structure of which renders the logical mode of presentation of the (“flat”) denotatum of an expression. Hence meaning is conceived as a concept represented by the expression, i.e. a construction in the canonical normal form. An adjustment of Materna’s theory of concepts is first proposed, so that our analysis of a non-homonymous expression might be unambiguous (on the assumption of a fixed conceptual system — a common basis of our understanding each other). Synonymy, homonymy and equivalence of expressions are defined and a special case of the so-called hidden homonymy is examined. Using TIL, explicit intensionalisation enables us to precisely define the de dicto / de re distinction and prove two de re principles. Traditional hard nuts to crack, namely de dicto / de re attitudes and modalities are solved and we present logical reasons for not allowing β-reduction in the de re cases. In other words, we prove that β-conversion is not an equivalent transformation when working with partial functions. Logical independence of de dicto and / de re attitudes is illustrated, but a claim is proved that on an additional assumption the de dicto and the corresponding de re attitude are equivalent. Quine’s example of an ambiguity in belief attribution consisting in scope for the existential quantifier is analysed and we show that it actually does concern the de dicto / de re distinction, this time in the supposition of the existence predicate. Last but not least, we present a “hesitant plea for partiality”, though many technical difficulties (e.g. non-valid de Morgan laws) connected with partial functions are illustrated. The task of the logician is to undertake a precise analysis in order that all and only the logical consequences of our statements can be derived, even at the cost of some “technical difficulties”. Key-words: Structured meanings, concepts, synonymy, homonymy, equivalence, de dicto / de re supposition, de dicto / de re propositional attitudes, modalities, existence and de dicto / de re, lambda-transformation, partial functions.