Wahdat al-wujud, the unity of being, is the doctrine most associated with the Andalusian Sufi Ibn Arabi, though the phrase itself was coined by later commentators systematizing his writing rather than by Ibn Arabi as a slogan of his own. The core claim is that only God possesses true wujud, existence, and that everything else, the entire created world, has no independent being of its own but is a manifestation, a self-disclosure, of the single reality that alone truly exists. On this reading the multiplicity experienced in ordinary life is real as appearance but not as substance, comparable to the many waves on a single ocean, each distinct in form and each nothing other than the water it is made of.
Ibn Arabi developed the idea through an elaborate vocabulary, including the barzakh, an isthmus between absolute unity and the created plurality, and the doctrine of the perfect human, al-insan al-kamil, the figure in whom the divine names find their fullest mirror. His major works, especially the Meccan Illuminations and the Bezels of Wisdom, spread the doctrine across the Islamic world through students and commentators long after his death in 1240. Later Sufi orders across the Persian and Ottoman worlds transmitted the doctrine largely through commentaries on his work rather than through the notoriously difficult original texts themselves.