The principle of evidential existentiality in Philosophy is a principle that explains and gives value to the existence of entities. The principle states that the reality of an entity's existence gives greater value to prove its existence than would be given through any outward studies. The principle has become a backbone of the God argument, stating that because God is a self-evident entity, His existence can only be shared by humans, thus proof of God is unnecessary and moot.
Also a linguistics concept: Rubovitz, Tali (1999). "Evidential-existentials: The interaction between discourse and sentence structure". Journal of Pragmatics31 (8): 1025–1040. doi:10.1016/S0378-2166(99)00038-7. ISSN0378-2166.