Because Latin unio mystica became the standard term in Western academic comparative religion for any account of intimate union between a devotee and the divine, scholars of religion regularly borrow it to describe states in other traditions that use their own native vocabulary: Sufi fana, the passing away of the self in God; Hindu union with Brahman in some devotional and non dualist schools; Kabbalistic devekut. This comparative usage is useful shorthand but flattens real differences, since the traditions disagree sharply on whether the union described preserves a distinct self at all, whether it is temporary or permanent, and whether the divine reality united with is personal or impersonal.
Within Christianity itself, unio mystica remains formally distinct from the beatific vision, the direct, unmediated sight of God traditionally reserved for the redeemed after death, since mystical union is understood as a foretaste available, rarely and briefly, within earthly life to a small number of advanced contemplatives, while the beatific vision is the permanent, general destiny of the saved. This atlas treats unio mystica as the Christian doctrine proper, cross referencing rather than merging it with the structurally comparable but doctrinally distinct states named in other traditions.