What eye can see the characteristics of tathāgatagarbha?

The tathāgatagarbha is formless and without marks, invisible to the physical eye, yet it can be seen by the mind eye, the wisdom eye, the dharma eye, and the Buddha eye. Among these, the wisdom eye, the dharma eye, and the Buddha eye are collectively called the mind eye; because of differences in wisdom, what these three eyes see differs greatly. How can the formless, markless substance of the tathāgatagarbha be seen? Although the substance of the tathāgatagarbha is invisible, it has a great many operational modes of activity and functional capacities. The operational modes of the tathāgatagarbha are also called mental activities and mental factors (caittas); its functional capacities are to accomplish the myriad dharmas and the infinitely many dharmas, to manifest the appearances of all dharmas, and to endow all dharmas with their corresponding functions. The wisdom eye, being shallower in wisdom than the dharma eye and the Buddha eye, and subject to obstructions, sees the modes of activity of the tathāgatagarbha only superficially and roughly; the dharma eye sees the modes of activity of the tathāgatagarbha broadly and in fine detail; the Buddha eye is perfect and unobstructed, seeing the complete modes of activity of the tathāgatagarbha in their entirety, so minutely that no dharma is unknown and no dharma is uncomprehended—illumining heaven and earth, perceiving even the finest hair.

The modes of activity of the tathāgatagarbha can be observed through direct perception; those who have not attained enlightenment cannot observe them, and can only speculate about the functions the tathāgatagarbha performs, unable to directly observe the modes of activity and functions of the tathāgatagarbha. From this point alone, one can completely determine whether a person is enlightened or not, and whether the enlightenment is genuine or false. The functional capacities of the tathāgatagarbha can be learned from the Buddhist sutras and from the teachings of the patriarchs and eminent masters, and can be imagined; through inference one can also deduce their general functions, but it is very difficult to deduce them in any finer detail. Fine details, if they cannot be obtained by hearing about them, must be obtained through one's own direct observation. Therefore, every practitioner who wishes to attain true great wisdom, possessing the wisdom eye and the dharma eye, must diligently cultivate precepts, meditation (samādhi), and wisdom, put in painstaking effort, and genuinely practice and realize the truth; only then can one have the merit and benefit of true liberation.