The existence of the immaterial world and its beings is supported by the Greek, Islamic, and Indian philosophers but there are some scholars who rejected it such as, Ibn Sina, Mohagheghe Damad, Molla Abdolrazaghe Lahiji, and Mir Fendereski. Some others have emphasized on the existence of that world as, Sheikh Eshragh, Mollasadra, Sabzevari. They have believed that there is an immaterial world between the spiritual and the physical world which its beings have form and quantity but no material. The creatures of the spiritual world are incorporeal and without any quantity and material. The beings of the physical world are corporeal with both quantity and material. The spiritual world is the most perfect and the immaterial world is in a subordinate position. The existence of the immaterial world is important in ontology, epistemology, and theology. There are lots of reasons to prove its existence such as the rule of possibe Eshraf.