  Khayyam in Risālah fi'l-wujūd writes that “existence is abstract (secondary) (i‘tibārī) by way of emanation.” In addition, section seventeen of this treatise, entitled “Existence is an Added Concept to Essence” states, “The traces of existence can be found in all things such as accidents and there is no doubt that existence is a concept added to essence, that is intelligible (Ḍarūrat al-taḍād fi'l-‘ālam wa'l-jabr wa'l-baqā‘, 111). Clearly Khayyam supports the principality of essence. By relying on reductio ad absurdum, he concludes that if essence were to be secondary, it would have to exist prior to itself, which is impossible. Khayyam states “essence is primary and nothing else,” because “essence was non-existent and then became existent.” He goes on to argue “essence does not need existence [to exist] and [its existence] is not in relation to an existent since [if] essence prior to existing was non-existing (ma‛dūm), then how can something need something else [in order to exist] prior to its existence?” (Ḍarūrat al-taḍād fi'l-‘ālam wa'l-jabr wa'l-baqā‘, 125).