This paper extends the investigations into logical properties of the quantified argument calculus (Quarc) by suggesting a series of proper subsystems which, although retaining the entire vocabulary of Quarc, restrict quantification in such a way as to make the result decidable. The proof of decidability is via a procedure that prunes the infinite branches of a derivation tree in what is a syntactic counterpart of semantic filtration. We demonstrate an application of one of these systems by showing that Aristotle’s assertoric (...) syllogistic is embeddable within, thus also providing another method of showing its decidability. (shrink)

The present article employs a model-theoretic semantics to interpret a fragment of the language of the Quantified Argument Calculus (Quarc), a recently introduced logical system whose main aim is capturing the structure of natural language sentences in a closer way than does the language of classical logic. The main contribution is an axiomatization for the set of formulas that are valid in all standard interpretations within the employed semantics.

We introduce a two-valued and a three-valued truth-valuational substitutional semantics for the Quantified Argument Calculus (Quarc). We then prove that the 2-valid arguments are identical to the 3-valid ones with strict-to-tolerant validity. Next, we introduce a Lemmon-style Natural Deduction system and prove the completeness of Quarc on both two- and three-valued versions, adapting Lindenbaum’s Lemma to truth-valuational semantics. We proceed to investigate the relations of three-valued Quarc and the Predicate Calculus (PC). Adding a logical predicate T to Quarc, true of (...) all singular arguments, allows us to represent PC quantification in Quarc and translate PC into Quarc, preserving validity. Introducing a weak existential quantifier into PC allows us to translate Quarc into PC, also preserving validity. However, unlike the translated systems, neither extended system can have a sound and complete proof system with Cut, supporting the claim that these are basically different calculi. (shrink)

U radu se nudi opis konteksta unutar kojeg je formuliran poznati dokaz za nužnost identiteta. Iznosi se formalni prikaz ovog dokaza kako ga je formulirao poznati filozof i logičar Saul Kripke. Također se razmatra gledište filozofa Allana Gibbarda koji nasuprot Kripkeu brani tvrdnju da neki iskazi identiteta mogu biti kontingentni. Osnovni cilj rada je upoznati domaćeg čitatelja s formalnim aspektom rasprave o nužnosti identiteta te dati kratki pregled konteksta unutar kojeg su formulirani argumenti za nužnost identiteta. In the paper, we (...) offer an overview of the context within which the well-known proof of the necessity of identity is formulated. A formal account of this proof is presented as formulated by the renowned philosopher and logician Saul Kripke. Furthermore, we discuss the account of the philosopher Allan Gibbard, who defends the claim that some statements of identity can be contingent. The main goal of the paper is to acquaint the readers who understand the Croatian language with the formal aspect of the discussion on the necessity of identity and to give a brief overview of the context within which the arguments for the necessity of identity are formulated. (shrink)