How can one realize tathāgatagarbha?

The tathāgatagarbha is a mental dharma without form or mark, not material form; therefore the tathāgatagarbha cannot be found in material form, and the eyes can never see the tathāgatagarbha. In fact, we can neither see the tathāgatagarbha nor feel it, smell it, hear it, or think of it; only through investigating Chan can one realize the functions and operations of the tathāgatagarbha. To realize the tathāgatagarbha, one must use the solitary consciousness (mano-vijñāna-eka-citta) and the manas to investigate, and only then can one discover that formless, markless mode of operation of the tathāgatagarbha.

In discovering the operation of the tathāgatagarbha, the more specific the better; the more specific it is, the deeper and subtler the wisdom. The most specific and most evident operation of the tathāgatagarbha is its function of giving rise to the feeling, perception, volitional formations, and consciousness of the six consciousnesses. The operation of the tathāgatagarbha outputting the seeds of the four great elements within the material body—apart from the Buddha, probably no one could observe it. On insentient objects, the operation of numerous tathāgatagarbhas outputting the seeds of the four great elements is even more impossible to observe. Then how can one realize one's own tathāgatagarbha, or realize the tathāgatagarbha of a single sentient being? The tathāgatagarbha has a perceiving-aspect (darśana-bhāga) and can see all dharmas; if it could not see all dharmas, it could not manifest, uphold, and change all dharmas. We need only engage in contemplative practice (vipaśyanā-caryā) to examine what differences there are between its perceiving-aspect and the seventh consciousness, what differences there are with the sixth consciousness, and what differences there are with the five consciousnesses—that is enough. Only by starting the contemplative practice and deliberation from here is there a way out, and only then can one find the answer one seeks.

Since the tathāgatagarbha can discern the faculties, the body, and the material world—all of which belong to material sense-objects, and it also includes sound, smell, taste, touch, and dharmas—and it discerns all the dharmas of the eighteen realms, then what content does it discern, and how does it discern? This is the fundamental point of entry for realizing the consciousness-only wisdom of the varieties of paths and omniscience (sarvākārajñatā). All dharmas are manifested by the tathāgatagarbha; before manifesting them, it must first see and discern them before it can manifest them—it is impossible for it to blindly manifest any dharma. What, then, is the manner and content of its seeing, and how does it operate? This is the key and the focal point for obtaining the consciousness-only wisdom of the varieties of paths and omniscience.