Nūru'l-Envār (the Light of Lights) refers to the Divine Essence of Allah, the Most High and Glorified. (Kāshānī, 98; Jāmiʿ, 103)
Accidental light (nūr-i āriz) is not self-sufficient in its own essence (it is not self-subsistent, but dependent on other existents). However, it is not dependent on the night either. It bestows its lights upon the barzakh (isthmuses), but it is something other than the barzakh. Nor is it the substance of the night.
Pure light (nūr-i maḥḍ) is living. That which is living is dārrāk-i faʿāl (whose activity is never incomplete, whose action always comes to fruition). Life is the manifestation of a thing for its own essence. In that ḥāl (spiritual state), pure light is living, and every living thing is pure light. The ḥaqīqa (inner reality) of the light in its essence is neither differentiated nor characterized by perfection or deficiency.
Lights are classified as mujarrad (immaterial) and non-mujarrad. Absolute perfection belongs to Nūru'l-Envār (the Light of Lights). It is the Living (al-Ḥayy) who perceives His own Essence by His own Essence, the Self-Sufficient (al-Ghanī) and the Finder (al-Wājid), the Nūru'l-Envār, and the Subduer (al-Qahhār) over all things, in whom there is no possibility (imkān) of non-existence (ʿadam) in Himself. He is the One whose Essence is not contingent upon any condition, the Unique One (waḥdānī) who is singular and unique. All else is dependent upon Him. (Rawḍa, 564)
The Ishrāqī (Illuminationist) is one who seeks to be adorned with Nūru'l-Envār, also called the Real (al-Ḥaqq), and to attain union with it. This union is realized by Allah either through an intermediary or directly, by the Real Himself. (Rawḍa, 621)