Jiří Raclavský

Conceptual and derivation systems

Pavel Materna proposed valuable explications of concept and conceptual system. After their introduction, we contrast conceptual systems with (a novel notion of) derivation systems. Derivation systems differ from conceptual systems especially in including derivation rules. This enables us to show close connections among the realms of objects, their concepts, and reasoning with concepts.

Two Standard and Two Modal Squares of Opposition

In this study, we examine modern reading of the Square of Opposition by means of intensional logic. Explicit use of possible world semantics helps us to sharply discriminate between the standard and modal (‘alethic’) readings of categorical statements. We get thus two basic versions of the Square. The Modal Square has not been introduced in the contemporary debate yet and so it is in the centre of interest. Some properties ascribed by medieval logicians to the Square require a shift from its Standard to Modal version. Not inevitably, because for each of the two squares there exists its mate which can be easily confused with it. The discrimination between the initial and modified versions of the Standard and Modal Square enable us to separate findings about properties of the Square into four groups, which makes their proper comparison possible. The disambiguation so achieved leads to the solution of various puzzles often mentioned in recent literature.

Existential Import and Relations of Categorical and Modal Categorical Statements

I examine the familiar quadruple of categorical statements “Every F is/is not G.”, “Some F is/is not G.” as well as the quadruple of their modal versions “Necessarily, every F is/is not G.”, “Possibly, some F is/is not G.”. I focus on their existential import and its impact on the resulting Squares of Opposition. Though my construal of existential import follows modern approach, I add some extra details which are enabled by framing my definition of existential import within expressively rich higher-order partial type logic. As regards the modal categorical statements, I find that so-called void properties bring existential import to them, so they are the only properties which invalidate subalternation, and thus also contrariety and subcontrariety, in the corresponding Square of Opposition.

Explicating the Notion of Truth Within Transparent Intensional Logic

The approach of Transparent Intensional Logic to truth differs significantly from rivalling approaches. The notion of truth is explicated by a three-level system of notions whereas the upper-level notions depend on the lower-level ones. Truth of possible world propositions lies in the bottom. Truth of hyperintensional entities—called constructions—which determine propositions is dependent on it. Truth of expressions depends on truth of their meanings; the meanings are explicated as constructions. The approach thus adopts a particular hyperintensional theory of meanings; truth of extralinguistic items is taken as primary. Truth of expressions is also dependent, either explicitly or implicitly, on language (its notion is thus also explicated within the approach). On each level, strong and weak variants of the notions are distinguished because the approach employs the Principle of Bivalence which adopts partiality. Since the formation of functions and constructions is non-circular, the system is framed within a ramified type theory having foundations in simple theory of types. The explication is immune to all forms of the Liar paradox. The definitions of notions of truth provided here are derivation rules of Pavel Tichý’s system of deduction.

On the interaction of semantics and deduction in Transparent Intensional Logic (Is Tichý's logic a logic?)

It is sometimes objected that Tichý’s logic is not a logic because it underestimates deduction, providing only logical analyses of expressions. I argue that this opinion is wrong. First of all, to detect valid arguments, which are formulated in a language, there needs to be logical analysis to ascertain which semantical entities (Tichý’s so-called constructions) are involved. Entailment is defined as an extralinguistic affair relating those constructions. The validity of an argument, composed of propositional constructions, stems from the properties of the constructions. Such properties are displayed by the derivation rules of Tichý’s system of deduction.

Semantic concept of existential presupposition

Strawson’s work seems to contain both pragmatic and semantic concepts of presupposition. The former concept has largely been studied by many philosophers and linguists, while the latter has not been properly investigated (van Fraassen being an exception). The present author explicates the semantic concept of existential presupposition in relation to deriving existential statements and distinguishing their de dicto/de re variants (in the rather generalized sense following Tichý).

Pravda a paradox: úvod do problematiky

Tato stať je zamýslena jako uvod do spojite problematiky explikace pravdivosti a semantic-kých paradoxů, ktere onu explikaci pronasleduji. Tyto paradoxy jsou viděny jako prostředek ukazani, že nedostatecně promyslena explikace naseho pojmu pravdivosti (významu pravdi-vostniho predikatu) je explikaci nevyhovujici. Pote jsou předvedeny rysy obou klasických přistupů, Russellovy teorie typů a Tarskeho hierarchie metajazyků. Nakonec jsou podany za-kladni ideje hlavnich nazorových skol, ktere přisly pote.