Paolo Valore

Ponto de partida do presente artigo é uma interrogação acerca do significado existencial das proposições. Em primeiro lugar, é considerada a ideia de existência simbólica na lógica de MacColl, ao mesmo tempo que se assinalam os problemas que, na perspectiva de Bertrand Russell, estão associados com a auta-referência e o significado da classe-nula. Por outro lado, o artigo demonstra também até que ponto a própria perspectiva de Russell não está livre de problemas, de ambiguidades e de mudanças de opinião. O autor do artigo partilha a crítica de Russell sobre o significado do quantificador, acabando por usar Russell contra Russell, ou seja, a réplica russelliana de 1957 a G. J. Warnock contra a réplica russelliana de 1905 a MacColl. Assim, a partir de uma análise lógica do debate entre Russell e MacColl, o artigo procede a uma investigação da relação entre Lógica e Ontologia, considerando de um modo especial o caso dos objectos não-existentes. /// Moving from a technical, logical point of view in the RusselUMacColl debate about the existential import of propositions and the significance of the null-class, the paper tries to inquiry the relationship between logic and ontology, considering in special the case ofnon existing objects, Russell's philosophical treatment of the existential quantification gains his full meaning in his realistic perspective. But it is possible to use this treatment versus Russell intentions, to deny that there is a supplementary (in space-time) existence, that "lies wholly outside Symbolic Logic".

Scientific literature on particular themes in ontology is extremely abundant, but it is often very hard for freshmen or sophomores to find a red thread between the various proposals. This text is an opinionated introduction, a preliminary text to research in ontology from the so called standard approach to ontological commitment, that is from the particular point of view that connects ontological questions to quantificational questions. It offers a survey of this viewpoint in ontology together with their possible applications through a broad array of examples and open problems and, at the same time, essential references to the classics of philosophy, so as to allow non-specialists to understand the terms and analysis procedures characterizing the discipline. Its result is a wide-ranging overview of the issued tackled by ontology, with a particular focus on the most relevant problems of contemporary debate.