Room P3.10, Mathematics Building

Sanderson Molick, UFRN - Brasil

Bivalence and Many-valuedness: a glimpse on Suszko's thesis and its developments

Many-valued logics received several criticism since its birth. Among the main opponents to its creation there is the Polish logician Roman Suszko. In the mid 70s, at a conferece held in Cracow, he called into question the nature of many-valuedness by claiming the existence of “only but two truth values”, a statement nowadays regarded as Suszko's Thesis, and stated that “after 50 years we still face an illogical paradise of many truths and falsehoods”. Suszko's motivation for his ideas lies in defending the existence of a double semantic role expressed by truth values. This duplicity is revealed by him in drawing the difference between algebraic and logical values. According to him, even though we can have more than two algebraic values, there are only two genuine logical ones. The philosophical content of his ideas finds support in a well know result called Suszko's reduction, a theorem that affirms every tarskian logic is two-valued. Several contributions emerged from Suszko's ideas. It is the purpose of the present talk to expose some of these main developments. At first, it will be shown some results that corroborates Suszko's ideas and present some limitations to them. Lastly, some discussions and comments regarding Suszko's thesis will be shown.