In Ayn-al-Qużāt Hamadānī's ontological system, two conceptions of plurality and unity of existence have been separated. The first has been presented when he tried to argue for the existence of necessary being and in doing that he divided existence into two categories: eternal vs. originated. A precondition of such a division is to accept the idea of plurality of existence. The second conception has been presented where Ayn-al-Qużāt confined existence to the existence of God and considered Him as the only true and real example of existence. According to this conception, pluralities are essentially nonexistent and are nothing but epiphanies of God. Therefore, the relationship between them and God is like the relationship between manifested appearances and manifestation itself, not between two independent objects. Accordingly, there is no otherness or plurality in the realm of existence. However, by taking into account the differentiation that Ayn-al-Qużāt suggests between Stage of Reason and Domain of beyond Reason, it can be claimed that plurality of existence is connected with the former and its unity is connected with the latter. This means that the difference between plurality and unity of existence is epistemological, not ontological, according to Ayn-al-Qużāt