Numa iniciativa conjunta da Sociedade Brasileira de Lógica e do Grupo de Interesse em Lógica da Sociedade Brasileira de Computação, gostaríamos de convidar a todos a participarem do Seminário "Lógicos em Quarentena". Trata-se de um seminário remoto com apresentações informais por membros da comunidade e espaço para perguntas no fim. As apresentações usualmente são gravadas e disponibilizadas na página do evento http://lq.sbl.org.br (com a agenda completa).
Data: 26 de novembro de 2020 (quinta-feira) Horário: 16:00h GMT-3 Apresentador: Jean-Yves Beziau (DF/UFRJ) Título: The Mystery of the Fifth Logical Notion <http://jyb-logic.org/ALICE>Resumo: We discuss a theory presented in a posthumous paper by Alfred Tarski entitled “What are logical notions?”. Although the theory of these logical notions is something outside of the main stream of logic, not presented in logic textbooks, it is a very interesting theory and can easily be understood by anybody, especially studying the simplest case of the four basic logical notions. This is what we are doing here, as well as introducing a challenging fifth logical notion. We first recall the context and origin of what are here called Tarski-Lindenbaum logical notions. In the second part, we present these notions in the simple case of a binary relation. In the third part, we examine in which sense these are considered as logical notions contrasting them with an example of a non-logical relation. In the fourth part, we discuss the formulations of the four logical notions in natural language and in first-order logic without equality, emphasizing the fact that two of the four logical notions cannot be expressed in this formal language. In the fifth part, we discuss the relations between these notions using the theory of the square of opposition. In the sixth part, we introduce the notion of variety corresponding to all non-logical notions and we argue that it can be considered as a logical notion because it is invariant, always referring to the same class of structures. In the seventh part, we present an enigma: is variety formalizable in first-order logic without equality? A apresentação ocorrerá pelo Google Meet através do link público https://meet.google.com/jnp-yieh-nnf . -- Bruno Lopes Professor Adjunto Instituto de Computação Universidade Federal Fluminense http://www.ic.uff.br/~bruno -- Você está recebendo esta mensagem porque se inscreveu no grupo "LOGICA-L" dos Grupos do Google. Para cancelar inscrição nesse grupo e parar de receber e-mails dele, envie um e-mail para [email protected]. Para ver esta discussão na web, acesse https://groups.google.com/a/dimap.ufrn.br/d/msgid/logica-l/CAD-Wq08JphCw7SWT_-EC8gVsxy5_iq_Q7%2BF%3DmLZLT-5pcQBGdQ%40mail.gmail.com.
