dialetheist

Dialetheism is the view in philosophy of logic that there exist sentences which are both true and false at the same time. In other words, some contradictions are true. This position challenges the classical logic view that the law of non-contradiction is universally valid and that from a contradiction anything follows (the principle of explosion).

Dialetheism is often associated with paraconsistent logics, formal systems that avoid explosion and allow inconsistencies to be studied without collapsing into triviality. Proponents argue that these logics better handle certain semantic paradoxes and troubling limits of truth, such as the liar paradox. A standard informal example is the sentence “This sentence is false,” which dialetheists may treat as both true and false.

Modern dialetheism is closely linked to the work of philosopher Graham Priest, who has defended the view and helped popularize related paraconsistent logics, such as the Logic of Paradox (LP). The position is part of a broader discussion about how truth, meaning, and contradiction should be understood in natural language and formal theories.

Critics contend that accepting true contradictions undermines important notions of truth and can threaten reliable reasoning. They often argue that even paraconsistent logics must avoid triviality or that it is preferable to refine our theories of truth and reference instead of embracing contradictions. The debate between dialetheists and their critics continues within philosophy of logic and semantics, reflecting deeper questions about the nature of truth and inconsistency.