Edward N. Zalta 2 aletheists argue that some sentences are both true and false, and that sometimes appearances are not deceiving—there just are special groups of true yet jointly incompatible sentences for which the contradiction they In Defense of the Law of Noncontradiction imply is both true and false. We shall suppose, for the purposes of this paper, that the law of noncontradiction is the claim that there are no ∗ true contradictions. Thus, dialetheism is the view that the law of non- Edward N. Zalta contradiction is false. While there are plenty of philosophers who accept, Center for the Study of Language and Information and work within, paraconsistent logic, only a few count themselves as Stanford University dialetheists.
[email protected] I take paraconsistent logic and dialetheism seriously, and think that they offer a philosophically worthy approach to these puzzling groups of sentences. The logical investigation of paraconsistent logic is certainly An important philosophical puzzle arises whenever we find a group interesting and justified. We should endeavor to know what are the of philosophically interesting sentences which individually appear to be metatheoretical features of this logic. Dialetheism also deserves careful true but jointly imply a contradiction. It is traditional to suppose that study. Truth value gluts may be no worse than truth value gaps,1 and it since the sentences in the group are jointly inconsistent, we cannot accept is always good to investigate whether, or why, philosophers just take it them all. This refusal to accept all the sentences in the group is not just on faith that no contradictions are true.