SUBJECT & OBJECTIVES: There are two main theories about the reality of existence discussed in Islamic philosophy and mysticism, namely the Gradation of Existence and the Unity of Existence. This dispute has very important implications for the human worldview. This study is aimed to answer the following basic questions: Which of these theories is correct? Is there textual evidence from verses and narrations to support one of them? What are the implications of these theories? METHOD & FINDING: The study is based on the descriptive analytical method of analyzing available data in the library. This article compares two important schools of thought about a specific issue. CONCLUSION: The Gradation and Unity of Existence are two theories that interpret the reality of multiplicity in this universe. Both have their own rational and revelational evidence to prove themselves. Most philosophers, especially the followers of the Transcendent Wisdom of Mulla Sadra, believe that the unity of existence is the perfect version that can interpret many issues in a better way. Two theories have differences in interpretation of the monotheism of God at different levels, reality of contingent beings, creation of God as emanation or manifestation, gradation of existence or manifestation, etc.
