Abstract

One of the most important philosophical problems - and perhaps the most important of all-is the discussion of quiddity and existence and their relations to each other. After Farabi, Ibn Sina has dealt with quiddity and the quality of its belonging to existence in his works. Later, Nasir al din Tusi confirms Shaikh's view in response to Fakhr razi's objections to Ibn Sina's views. Meanwhile Ibn Rushd has sometimes put forward criticisms against the views of Ibn Sina and Ghazzali. It seems that the debate about the problem of quiddity and existence derives from a confusion between epistemology and ontology. The explanation how the mental ideas originate by way of causality and the effects between external objects-whether sensual or extra- sensual-and bodily organs and perceptual faculties of soul clearly shows that only "outside" exists and mental ideas created from it in the mind. Therefore, there remains no room for the subject of so-called quiddity, its relation with existence, its attribution by existence and many other problems derived from this subject.