The Meaning of "When Perfect Brightness Illuminates, the Object of Arising Is Established; Once the Object Is Established, the Illuminating Nature Perishes" in the Śūraṅgama Sūtra

The perfectly luminous and wondrous bodhi light shines upon the dharmāyatana that He gives rise to. If someone takes this dharmāyatana as truly existent, as a real and indestructible dharma, as self or as belonging to self, then it is like a single leaf covering the eye—seeing only the false and not the true, unable to see the radiance of the wondrous luminous true mind, the self-nature of the fundamental essence. Thus birth and death flow on without cease.

When you write words on a blackboard with a piece of chalk, what are those words? They are all just the chalk's powder. If you recognize only the words and not the chalk, the chalk's dust is obscured. The chalk is a metaphor for the self-natured pure mind, the perfectly wondrous luminous true mind; the chalk dust is a metaphor for the self-nature's radiance; the words on the blackboard are a metaphor for worldly dharmas; and the blackboard is a metaphor for the worldly realm.