Existential instantiation

In predicate logic, existential instantiation (also called existential elimination)[1][2] is a rule of inference which says that, given a formula of the formfor a new constant symbol c. The rule has the restrictions that the constant c introduced by the rule must be a new term that has not occurred earlier in the proof, and it also must not occur in the conclusion of the proof.must be uniformly replaced by c. This is implied by the notation, but its explicit statement is often left out of explanations.In one formal notation, the rule may be denoted by where a is a new constant symbol that has not appeared in the proof.
Rule of inferencePredicate logicTransformation rulesPropositional calculusRules of inferenceImplication introductionelimination (modus ponens)Biconditional introductioneliminationConjunction introductionDisjunction introductionDisjunctivehypothetical syllogismConstructivedestructive dilemmaAbsorptionmodus tollensmodus ponendo tollensNegation introductionRules of replacementDouble negationDe Morgan's lawsTranspositionMaterial implicationExportationTautologyUniversal generalizationinstantiationExistential generalizationExistential fallacyUniversal instantiationList of rules of inferencePrentice Hall