double-negation-introduction (math concept)
See also
python declaration class | python inclusion class | python sample
Definition
double-negation-introduction is the well-known and valid inference-rule:
\[\boldsymbol{P} \vdash \lnot \left( \lnot \left( \boldsymbol{P} \right) \right)\]
Quotes
“The rule of double negation introduction is a valid argument in types of logic dealing with negation ¬. This includes propositional logic and predicate logic, and in particular natural deduction. As a proof rule it is expressed in the form: If we can conclude ϕ, then we may infer ¬¬ϕ.” - [ProofWiki22a]