In predicate logic, existential instantiation (also called existential elimination) is a valid rule of inference which says that, given a formula of the form , one may infer for a new constant symbol c. The rule has the restriction that the constant c introduced by the rule must be a new term that has not occurred earlier in the proof.
|Rules of inference|
|Rules of replacement|
In one formal notation, the rule may be denoted by
where a is a new constant symbol that has not appeared in the proof.
- Hurley, Patrick. A Concise Introduction to Logic. Wadsworth Pub Co, 2008.
- Copi and Cohen
- Moore and Parker