2020-01-152020-01-152008-06SANZ, Wagner Campos. Negação e Falsidade. O Que nos Faz Pensar, Rio de Janeiro, n. 23, p. 153-162, jun. 2008.e- 0104-6675http://repositorio.bc.ufg.br/handle/ri/18515We examine the concept of falsity and the concept of negation. We show that it is possible to formulate a version of Peano Arithmetic for refutability which is structurally identical with the system for provability. After doing this we consider De Morgan’s laws, which seem to be behind these structural similarities, trying to formulate such laws in a unified and complete fashion for all usual first order logical constants. These results bring out some questions of a philosophical nature.engAcesso AbertoNegaçãoFalsidadeLeis de DeMorganAritmética de PeanoRefutabilidadeNegationFalsityDeMorgan’s lawsPeano arithmeticRefutabilityArtigo