The paper presents a contra-classical dialectic logic, inspired and motivated by Hegel s dialectics. Its axiom schemes are 0.1 Thus, in a sense, this dialectic logic is a kind of “mirror image“ of connexive logic. The informal interpretation of ‘ $$\rightarrow $$ ’ emerging from the above four axiom schemes is not of a conditional (or implication); rather, it is the relation of determination in the presence of truth-value gaps: $$\varphi \rightarrow \psi $$ is read as $$\varphi $$ determines $$\psi (...) $$, namely, necessarily, if $$\varphi $$ is true, then $$\psi $$ is either true or false, not gappy. As far as I know, such a connective has not been considered before in the literature. (shrink)

The aim of this paper is to lay bare the roots of dialetheism in discussions about dialectics and dialectical logic at the time of the first development of paraconsistent logics. In other words, th...

I propose a comprehensive account of negation as a modal operator, vindicating a moderate logical pluralism. Negation is taken as a quantifier on worlds, restricted by an accessibility relation encoding the basic concept of compatibility. This latter captures the core meaning of the operator. While some candidate negations are then ruled out as violating plausible constraints on compatibility, different specifications of the notion of world support different logical conducts for negations. The approach unifies in a philosophically motivated picture the following (...) results: nothing can be called a negation properly if it does not satisfy Contraposition and Double Negation Introduction; the pair consisting of two split or Galois negations encodes a distinction without a difference; some paraconsistent negations also fail to count as real negations, but others may; intuitionistic negation qualifies as real negation, and classical Boolean negation does as well, to the extent that constructivist and paraconsistent doubts on it do not turn on the basic concept of compatibility but rather on the interpretation of worlds. (shrink)

The claim that nature is self-consistent has recently been contested by a number of paraconsistent logicians. In this paper I will survey the arguments which paraconsistent logicians have presented for the thesis that nature is actually inconsistent. My conclusion is that these arguments all fail.The paraconsistency programme has to date been concerned primarily with outlining the philosophical inadequacy of classical logic, and detailed discussions of issues bearing upon the philosophical adequacy of the paraconsistency position itself are not to be found (...) as yet in the literature. This inadequacy will be illustrated here with respect to the question of the self-consistency of nature. (shrink)

Da Costa's C systems are surveyed and motivated, and significant failings of the systems are indicated. Variations are then made on these systems in an attempt to surmount their defects and limitations. The main system to emerge from this effort, system CC , is investigated in some detail, and dual-intuitionistic semantical analyses are developed for it and surrounding systems. These semantics are then adapted for the original C systems, first in a rather unilluminating relational fashion, subsequently in a more illuminating (...) way through the introduction of impossible situations where and and or change roles. Finally other attempts to break out of impasses for the original and expanded C systems, by going inside them, are looked at, and further research directions suggested. (shrink)

In celebration of Newton da Costa’s place in the history of paraconsistency, this paper considers the use and abuse of deliberate self-contradiction. Beginning with Parmenides, developed by Plato, and continued by Cicero, an ancient philosophical tradition used deliberately paraconsistent discourses to reveal the truth. In modern times, decisionism has used deliberate self-contradiction against Judeo-Christian revelation. • DOI:10.5007/1808-1711.2010v14n1p1.

This paper develops the first deontic logic in the context of paraconsistent logics.

Negation is widely thought to be uniquely captured by the usual extensional Boolean connective in the setting of classical logic. However, there has been recent interest in a modal approach to negation. This essay examines the problem of modal negation with an Husserlian phenomenological lens. I argue that the Husserlian approach to negation contains an ambiguity which points to a pluralism about negation. On this view, negation begins its life as a modal notion with nonclassical properties, and the question of (...) classical negation is a question of its demodalization. I reconstruct a phenomenological legitimation of the demodalization, but I remain skeptical about its wider prospects. Nevertheless, the phenomenological-modal approach to negation answers the skepticism about the very possibility of debates about negation and gives valuable insight into the fundamental nature of the problem. The argument should be of interest both to those who are specifically interested in Husserl's logic and the relationship of phenomenology to intuitionistic (and other nonclassical) logics, as well as to philosophers of logic more generally interested in obtaining different angles on the problem of negation from a systematic perspective. (shrink)