2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/92341It is well known that in Zermelo-Fraenkel (ZF) set theory any finite set is decidable. In this paper we discuss an extension of ZF where this result is no longer valid. Such an extension is quasi-set theory and it has its origin on problems motivated by quantum mechanics.9 pages, no figuresQuantum Physicstext