The Judeo-Christian mystical tradition is replete with accounts of visions. But the perceptual experiences reputedly involved in these visions are often problematic. The prophet Isaiah (of Jerusalem) is reputed to have seen God in a mystic vision; St Francis to have seen Christ and received the stigmata; Julian of Norwich to have seen Christ's passion; St Teresa of Avila to have seen Christ, the devil, seraphim, and various Saints. Yet at least two fundamental questions immediately arise concerning the perceptual awareness involved in such visionary experiences. First, how could Jewish or Christian mystics have any reasonable certitude of correctly identifying such extraordinary entities as God, angels, and deceased Saints, as figures in their visions? And second, while Catholics, for example, see the Virgin Mary during their visions, Muslims see Muslim saints and Hindus see Hindu deities: why then do mystics tend during their visions to perceive entities which accord with their expectations, entities which are usually regarded as possessing special religious significance exclusively within each mystic's own religious tradition?