A proper understanding of the Sufi doctrine of the unity of existence is essential for following the later developments of Islamic philosophy. The doctrine of the unity of existence is divided into introversive and extroversive aspects, the former dealing with the unity of the soul of the mystic with God, and the latter with the unity of the cosmos with God. Here this latter aspect of the doctrine is explained through a comparison of the views of Ibn ‘Arabi and Meister Eckhart, both of whom are profoundly influenced by Ibn Sina at precisely the same crucial points, although Meister Eckhart makes explicit reference to Ibn Sina, while Ibn ‘Arabi generally avoids naming him. The theory of the extroversive unity of existence consists of four parts, or rather, it is the product of four steps, each of which is logically based on the previous one: (1) God is the only being or the absolute existence. (2) Everything other than God (i. e., human beings and the cosmos) is nothing or nonexistence. (3) The existence of all things is God’s existence (All are He). (4) The cosmos does not have existence but manifests existence. In other words, it is God’s self-disclosure.