In this introduction to the special issue “40 years of FDE”, we offer an overview of the field
and put the papers included in the special issue into perspective. More specifically, we first …

Negation is in the first place a phenomenon of semantic opposition. As such, negation
relates an expression\(e\) to another expression with a meaning that is in some way …

Many prominent systems of non-classical logic are subsystems of what is generally called
'classical logic.'Systems of connexive logic are contra-classical in the sense that they are …

A kind of a bi-intuitionistic propositional logic is introduced that combines verification and its
dual. This logic, 2Int, is motivated by a certain dualization of the natural deduction rules for …

In this paper we will consider the existing notions of bilateralism in the context of proof-
theoretic semantics and propose, based on our understanding of bilateralism, an extension …

Various four-and three-valued modal propositional logics are studied. The basic systems are
modal extensions BK and BS4 of Belnap and Dunn's four-valued logic of firstdegree …

In this paper, a family of paraconsistent propositional logics with constructive negation,
constructive implication, and constructive co-implication is introduced. Although some …

Over the past ten years, the community researching connexive logics is rapidly growing and
a number of papers have been published. However, when it comes to the terminology used …

Connexive logic has room for two pairs of universal and particular quantifiers: one pair, and,
are standard quantifiers; the other pair, and, are unorthodox, but we argue, are well …

Despite the tendency to be otherwise, some non-classical logics are known to validate
formulas that are invalid in classical logic. A subclass of such systems even possesses pairs …