The Śūraṅgama Sūtra, Volume 3: The Eye Faculty Is Fundamentally the Wonderful True Suchness Nature of the Tathāgatagarbha

Original text: 复次阿难。云何六入。本如来藏。妙真如性。阿难。即彼目睛。瞪发劳者。兼目与劳。同是菩提。瞪发劳相。因于明暗。二种妄尘。发见居中。吸此尘象。名为见性。此见离彼。明暗二尘。毕竟无体。

Explanation: Furthermore, Ānanda, why are the six sense bases originally the wondrous true suchness nature of the tathāgatagarbha? Ānanda, it is your eyes staring at objects that gives rise to the mark of activity, the mark of exertion, the mark of operation; the eyes are the eye faculty, and the mark of exertion is the aggregate of volitional formations—both are marks of exertive contact manifested and revealed by the wondrous bodhi. Relying on the two kinds of false sense-objects, brightness and darkness, the eye faculty contacts material sense-objects, and within this the seeing nature of the eye arises; this seeing nature absorbs these sense-objects and thereby manifests them—this is called the seeing nature. Apart from the two kinds of false sense-objects, brightness and darkness, this seeing nature fundamentally has no substance of seeing.

From the very beginning the Buddha explains how the six sense bases are the wondrous true suchness nature of the tathāgatagarbha, which means that the six sense bases in their entirety are produced by the tathāgatagarbha and are functional attributes of the tathāgatagarbha; therefore, from within the six sense bases one can discover the functions and operations of the tathāgatagarbha and realize the tathāgatagarbha. The mark of activity and the mark of exertive contact of the eye faculty and the manas are the wondrous true suchness nature; the seeing nature that is produced is the wondrous true suchness nature; moreover, the two conditions of brightness and darkness that give rise to the seeing nature are also the wondrous true suchness nature. Whatever sentient beings see, contact, and make use of is all the wondrous true suchness nature—there is no dharma that is not the wondrous true suchness nature. Realizing the tathāgatagarbha is actually not difficult; His traces are everywhere, and He does not hide. The key lies in the state of sentient beings' own karmic obstructions: whether the causal conditions for seeing the nature are fully mature, whether the bodhisattva nature is complete, and whether precepts, meditative concentration (samādhi), and wisdom are fully complete—this is where the difficulty lies.

Original text: 如是阿难。当知是见。非明暗来。非于根出。不于空生。何以故。若从明来。暗即随灭。应非见暗。若从暗来。明即随灭。应无见明。若从根生。必无明暗。如是见精。本无自性。若于空出。前瞩尘象。归当见根。又空自观。何关汝入。是故当知。眼入虚妄。本非因缘。非自然性。

Explanation: Thus, Ānanda, you should know that this seeing nature does not come from the two marks of brightness and darkness, is not produced from the eye faculty, and is not born from empty space. Why is this said? If the seeing nature were produced from brightness, then when darkness arrives the seeing nature would vanish and cease to exist, and thus it could not see darkness, nor would it know darkness. If the seeing nature were produced from darkness, then when brightness appears the seeing nature would disappear, and thus it could not see brightness. If the seeing nature were produced from the eye faculty, there would necessarily be no marks of brightness and darkness; such a seeing essence would fundamentally have no self-nature of its own. If the seeing nature were produced from empty space, then looking forward it sees the images of sense-objects, and upon returning it should be able to see the eye faculty—yet the eye faculty is not seen. Moreover, if empty space itself could see, what would that have to do with your eye faculty? Therefore you should know that the eye base is false and illusory; it is fundamentally not produced from causes and conditions, nor is it a natural nature—it is rather the nature of the tathāgatagarbha.