In Book 1 of the Masnavi, Rumi employs the narrative of a guest presenting a mirror to Joseph as an allegory for the metaphysical relationship between existence and non-existence. The guest's logic—that Joseph's peerless beauty can only be appreciated through a mirror—introduces the concept that 'the mirror of being is non-being' ($adam$). Rumi argues that divine attributes are only manifest through their opposites: the tailor's skill requires unshaped timber, and the physician's art requires the sick. Consequently, human deficiency ($nuqs$) and 'non-being' serve as the essential mirrors reflecting God's absolute perfection ($kamāl$) and generosity. This framework posits that the recognition of one's own flaws is the primary catalyst for spiritual growth. Rumi warns that the 'conceit of perfection' is a spiritual death, as it prevents the soul from seeking the divine completion found only when one empties themselves of ego to become a clear reflector of the Divine.