The theory of personal unity of existence is the highest state of theoretical monotheism. Despite its long background, this theory has not had a systematic form in our tradition before Ibn Arabi and Qiinawi.In comparison to other past scholars' works, the theory has been discussed more clearly in Ibn Arabi's books. Some commentators like Qunawi, kashani, Qaysari, Jami, Seyyed Heydar Amuli and Ibn- Turke Isfahani modified and presented it as a theory on existence. Mulla Sadra accepted, confirmed and explained it in accordance with the criteria of wisdom, and raised two arguments to prove it. It is in fact the final view of Mulla Sadra. In comparison to it, we can consider the tradational unity of existence as an average theory. After Mulla Sadra some mystics, like Muhmmad Reza Qumshe'i, Seyyed Ahmad Karbaiayi, Mirza Ali Aqha Qazi, Imam Khomeyni and 'allameh Tabatabayi defended the theory according to which the real existence or existent is only the holy essence of God the Exalted, and others are His states, manifestations and appearances. Using the term 'existence' to them is not by essence, but by accident. Thus, firstly, sensible and intelligible multiplicities are not mere imaginations; rather, they exist outside of mind and are manifestations and appearances of existence, but their realities are not the very existence. Secondly, none of the multiplicities of this world has real existence; so attribution of pantheism and incarnation to the followers of this theory is incorrect. Nevertheless, different groups disagreed with the theory and criticized and rejected it because of the two mentioned points. In this article, the late' Allameh Ja' fari' s statements are analyzed and criticized. Relying on some of Mulla Sadra's views in Asrar, Ja'fari wrongly believed the theory necessitates pantheism and incarnation.