The Knowable Upādāna and Unknowable Upādāna of Tathāgatagarbha

The Unperceived Sustaining Power of the Tathagatagarbha is its function of upholding all dharmas, including the five aggregates and the eighteen elements. It is called "unperceived" because it is too subtle and hidden for sentient beings to recognize, yet Buddhas and Bodhisattvas thoroughly know it without doubt. For example, if a finger is severed but reattached within a short time, the finger can still function. Before reattachment, one's own Tathagatagarbha continues to sustain it; the severed finger still exhibits nerve activities, and its muscles do not become dead tissue. This sustaining function is the Unperceived Sustaining Power of the Tathagatagarbha.

If one becomes aware of this function of the Tathagatagarbha, it becomes the Perceived Sustaining Power. The bones in a grave that do not decompose are all sustained by the Tathagatagarbha; if the Tathagatagarbha ceased to sustain them, not even ashes would remain. Upon attaining Buddhahood, the sustaining function of the Tathagatagarbha is fully and clearly known to the Buddha; there is not a single dharma unknown to him. Therefore, whether it is "unperceived" depends on the observer: for the knower, it is the Perceived Sustaining Power; for the unknowing, it remains the Unperceived Sustaining Power.