To establish knowledge upon knowing and seeing is the root of ignorance; when knowing and seeing are free of seeing, that is nirvāṇa.

The Śūraṅgama Sūtra contains this saying: 知见立知，即无明本；知见无见，斯即涅槃。"To establish knowing upon knowing is the root of ignorance" means that all sentient beings have a mind of seeing, hearing, awareness, and knowing, which can see, can hear, can be aware, and can know. But if we take these faculties of knowing as real, establishing the knowing that perceives the six sense objects as true, as a permanent and imperishable self that can go on to future lives, then this view is a wrong view (mithyā-dṛṣṭi) and is the root of ignorance. In that case, one will transmigrate through the cycle of birth and death in the six realms, unable to attain liberation.

"When knowing is without knowing, that is nirvāṇa." If, through contemplative practice (vipaśyanā-caryā), we come to understand that these faculties of seeing, hearing, awareness, and knowing are all deluded minds subject to arising, ceasing, and change, which cannot abide permanently, cannot exist forever, and are not the true self, then the mind will no longer take the faculties of seeing, hearing, awareness, and knowing as the self. Once this view is firmly established, the self-view (ātma-dṛṣṭi) is eliminated, and in the future one can eliminate self-grasping and realize nirvāṇa without remainder (anupadhiśeṣa-nirvāṇa). If, upon the faculties of seeing, hearing, awareness, and knowing, one can realize that self-natured pure mind which itself possesses no faculty of seeing, hearing, awareness, or knowing, then one has realized the nirvāṇa that is originally pure in self-nature.

To explain this saying more precisely: "when knowing is without knowing" means that, alongside the various kinds of knowing and perceiving of the six consciousnesses, there is at the same time an original mind, the tathāgatagarbha, which possesses no knowing or perceiving whatsoever and has been operating behind the scenes all along; "that is nirvāṇa"—He is the unborn and unceasing original mind, the tathāgatagarbha, within the state of nirvāṇa, that is, the mind of nirvāṇa.