Key figure: Muhyiddin Ibn Arabi (~1165–1240 AD), Fusus al-Hikam (Bezels of Wisdom) and Futuhat al-Makkiyya (Meccan Revelations) — among the most influential and controversial works in Islamic intellectual history.

Wahdat al-Wujud (‘Unity of Existence’) is Ibn Arabi’s metaphysical doctrine: there is only one Being (wujud), and that Being is God. All existing things are manifestations (tajalliyat) or self-disclosures of the divine Being — not identical to God (Ibn Arabi insisted on this) but not truly separate either. The universe is God’s self-contemplation, the ‘mirror’ in which the divine attributes become visible. Every thing that exists is simultaneously a veil of God and a manifestation of God. This has striking parallels with Neoplatonism (emanation), Advaita Vedanta (non-duality), and aspects of Kabbalah (tzimtzum/contraction).

The controversy: Ibn Taymiyya (~1263–1328 AD) condemned Wahdat al-Wujud as indistinguishable from the heresy of hulul (incarnationism — God entering into created things) and from the pantheism that abolishes the Creator-creature distinction central to Islamic tawhid. Ibn Arabi’s defenders insisted the doctrine is about the unity of Being, not the identity of all things with God — a subtle but crucial distinction. Wahhabism and Salafism continue to condemn Ibn Arabi; traditional Sufi orders, much of Shia theology, and Ottoman religious culture embraced him. He is perhaps the most contested figure in Islamic intellectual history.