Understanding Cannot Replace Actual Realization

All dharmas of the five aggregates and eighteen realms are the nature of the tathāgatagarbha. This principle can only be gradually and thoroughly understood through contemplative practice (vipaśyanā-caryā) after personally realizing the tathāgatagarbha. If one merely uses the mind consciousness to imagine that there is a tathāgatagarbha performing some function or certain functions, then there is no way to observe the tathāgatagarbha's operation directly in the present, and no way to observe the tathāgatagarbha-nature of the five aggregates and eighteen realms. Understanding is, after all, merely understanding; imagination is, after all, merely imagination—neither can substitute for personal realization.

How the tathāgatagarbha records and stores seeds, and how it actualizes cause and effect—these all belong to the domain of the seed-wisdom of Consciousness-Only (唯识种智), and only bodhisattvas who have attained the bhūmis are capable of observing them through direct perception. The seed functions of the tathāgatagarbha, its function of manifesting the myriad worldly dharmas, and the functional operations of all the seeds of the tathāgatagarbha all belong to the domain of the seed-wisdom of Consciousness-Only, and only bodhisattvas on the bhūmis can observe them through direct perception. Pre-bhūmi bodhisattvas (pūrvabhūmika bodhisattvas), because their afflictions are heavy and their meditative concentration (samādhi) is insufficient, lack adequate wisdom; their sixth and seventh consciousnesses have not yet undergone the transformation of consciousness into wisdom, and thus they are powerless to observe these extremely profound and subtle dharma principles. Therefore, what is merely understood cannot substitute for direct observation.