I’ll give it a shot better than Britannica. Too bad you guys haven’t helped me design Lady Tektonica. rolls up sleeves & grunts
Real Def: The real existential fallacy is either 1 of 2 errors: 1) presupposing non-emptiness (existential import) of a term before establishing it is non-empty (deductively, inductively, or abductively), or 2) presupposing emptiness of a term after establishing its non-emptiness (deductively, inductively with at least one instance, or abductively as best explanation).
Because it is most certainly not a fallacy to require sound premises with non-empty affirmed terms. Calling that a fallacy is a monkeywrench in being, action, and meaning.