07th Expansion Wiki
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This article is about a reasoning technique in
Umineko When They Cry.
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The Devil's Proof (悪魔の証明 Akuma no Shōmei) is the logical dilemma that while evidence will prove the existence of something, the lack of evidence fails to disprove it.

The Devil is used to illustrate the principle, but as a legal term it's often applied in IP rights suits involving black box technologies, such as patented chemical processes for production and software source code. In court, the dilemma is resolved by either granting plaintiffs rights to gather information, or by subpoena of internal data from the defendant.

In the game between Battler and Beatrice, this is used as the main method to make arguments. The Human Side's victory condition is providing a theory that makes it possible to commit the murders on Rokkenjima without the supernatural methods, and failure to do so is treated as a win of the Witch Side. Human Side has no burden of proof and can use statements as broad as "unknown method by unknown human", as long as it presents some alternative to the supernatural explanation of each murder the Witch Side can't prove as false.

A declaration in Red Text may be used to resolve the dilemma. Hempel's Raven is used to counter it: if we accept the existence of a Devil enough to accuse it, but it remains unavailable for examination, then the only way to prove its guilt is to prove the innocence of everyone else. An inspection conducted with Detective's Authority will also eliminate a Devil's Proof; if evidence isn't presented to prove something, the possibility of it is considered to be eliminated.