Principality of Quiddity and Mentally Posited of Existence from View Point of Khayyam (Emphasizing on Semnani's Expression)

Despite of the fact that Umre Khayyam is a peripatetic, he has defended the principality of quiddity. He deems that qualification of quiddity with existence is because quiddity is created. This idea raises the doubt of neglecting a part of history of philosophy by its authors. Semnani criticizing Mulla Sadra, Sabzevari and Aqa Ali Mudarres,deems Khayyam the initiator of debate of fundamental reality of quiddity or existence; reconsiders his vies from Sadra’s view point and confirms his proves. This paper arranging and explaining Khayyam’s view point (in accordance with Semnani’s expression),verifies Semnani’s judgement (according to Khayyam’s view point). This search is fundamental and its method is a mixture of description, analysis and comparison.The results are:1-Shekhe Ishraq was under the impact of Khayyam. 2-against to Semnani’s view point, the ground of Khayyam’s claim is refusing of external occurrence of existence to quiddity, not opposing with fundamental reality of existence. And this is the basicdistinction betweenpoint of view of Khayyamand that of Mirdamad and Mullasadra in this issue.