When the perfect brightness of illumination gives rise to an object, once the object is established, the illuminating nature is lost.

The Śūraṅgama Sūtra says: 圆明照生所，所立照性亡。The perfectly luminous bodhi radiance shines upon the dharmāyatana that He gives birth 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—one sees the false and not the true, and fails to see the radiance of the wondrous luminous true mind of the fundamental nature. 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 powder of the chalk. If you only recognize the words and not the chalk, the chalk 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 radiance of self-nature; the words on the blackboard are a metaphor for worldly dharmas; and the blackboard is a metaphor for the worldly realm.