From Wikipedia, the free encyclopedia
Jump to: navigation, search


Dialetheism is not a system of formal logic; instead, it is a thesis about truth that influences the construction of a formal logic, often based on pre-existing systems. Introducing dialetheism has various consequences, depending on the theory into which it is introduced. For example, in traditional systems of logic (e.g., classical logic and intuitionistic logic), every statement becomes false if a contradiction is true; this means that such systems become trivialist when dialetheism is included as an axiom. Other logical systems do not explode in this manner when contradictions are introduced; such contradiction-tolerant systems are known as paraconsistent logics.

Graham Priest defines dialetheism as the view that there are true contradictions.[1] JC Beall is another advocate; his position differs from Priest's in advocating constructive (methodological) deflationism regarding the truth predicate.[2]


Dialetheism resolves certain paradoxes[edit]


Dialetheism and human reasoning[edit]



The inadequacy of dialetheism to model human thoughts is shown by the appearance of cognitive dissonances when facing real contradictions.

Apparent dialetheism in other philosophical doctrines[edit]


The Buddhist logic system named Catuṣkoṭi similarly implies that a statement and its negation may possibly co-exist.[5] [6]


Dialetheism may be a more accurate model of the physical world[edit]

This is a new area of study, so ideas are only just coming to light, but dialetheism allows the possibility that natural things may have contradictory properties. Whether Wave–particle duality is one such case is not established, but it is a possibility Are there non-semantic dialethia

Formal consequences[edit]

In some logics, we can show that taking a contradiction p \wedge \neg p as a premise (that is, taking as a premise the truth of both p and \neg p), we can prove any statement q. Indeed, since p is true, the statement p \vee q is true (by generalization). Taking p \vee q together with \neg p is a disjunctive syllogism from which we can conclude q. (This is often called the principle of explosion, since the truth of a contradiction makes the number of theorems in a system "explode".)




There are also dialetheic solutions to the sorites paradox.


One important criticism of dialetheism is that it fails to capture something crucial about negation and, consequently, disagreement. Imagine John's utterance of P. Sally's typical way of disagreeing with John is a consequent utterance of ¬P. Yet, if we accept dialetheism, Sally's so uttering does not prevent her from also accepting P; after all, P may be a dialetheia and therefore it and its negation are both true. The absoluteness of disagreement is lost. The dialetheist can respond by saying that disagreement can be displayed by uttering "¬P and, furthermore, P is not a dialetheia". Again, though, the dialetheist's own theory is his Achilles' heel: the most obvious codification of "P is not a dialetheia" is ¬(P & ¬P). But what if this itself is a dialetheia as well? One dialetheist response is to offer a distinction between assertion and rejection. This distinction might be hashed out in terms of the traditional distinction between logical qualities, or as a distinction between two illocutionary speech acts: assertion and rejection. Another criticism is that dialetheism cannot describe logical consequences because of its inability to describe hierarchies.[1]

Examples of True Contradictions that Dialetheists Accept[edit]



"All statements are true" is a false statement.

"There are no absolutes" is an absolute.

According to dialetheists, these statements are not derived from logic (which they say is false), but are instead descriptions of experience.

Modern Dialetheists[edit]


See also[edit]


  5. ^ http://www.iep.utm.edu/nagarjun/#H2



External links[edit]