Realizing the tathāgatagarbha is itself enlightenment—why is the transformation of the basis (āśraya-parāvṛtti) necessary?

Seeing the Way is divided into the seeing of the Way of the Great Vehicle and that of the Small Vehicle; it is not only the Great Vehicle that is called seeing the Way. Seeing the Way of the Great Vehicle is the realization of the tathāgatagarbha; realizing the tathāgatagarbha means seeing the path upon which the study and practice of the Great Vehicle depends. It is not that after realizing the tathāgatagarbha, one must additionally accomplish the transformation of the basis (āśraya-parāvṛtti) for it to count as enlightenment—realizing the tathāgatagarbha in that very moment is itself the realization. As for the transformation of the basis, after enlightenment there is indeed a need for gradual transformation of the basis. When the transformation of the basis is accomplished, one's mental disposition approaches the purity of the tathāgatagarbha, afflictions are eliminated, and in terms of wisdom one possesses the seed-wisdom (bīja-jñāna) of Yogācāra. In this way one enters the house of the Tathāgata and becomes a true son of the Buddha. 

If accomplishing the transformation of the basis were required for seeing one's true mind and attaining enlightenment, then realizing the tathāgatagarbha would not be enlightenment. Since it would not be enlightenment, there would be no realization of the tathāgatagarbha; rather, one would merely intellectually deduce that there is a tathāgatagarbha. A tathāgatagarbha arrived at by intellectual deduction carries no experiential benefit of its merits, and so one would then need to compare one's bodily, verbal, and mental actions against the purity of the tathāgatagarbha, in order to restrain the bodily, verbal, and mental actions of the seven consciousnesses. When restrained to a certain degree, such that one no longer creates evil karma out of afflictions, that would count as enlightenment. But such restraint, without genuine enlightenment, cannot possibly succeed, and thus the so-called transformation of the basis would likewise never succeed. Without enlightenment, how could the transformation of the basis be accomplished? And after enlightenment, why would one need to accomplish the transformation of the basis again, and then establish that as enlightenment? Is this not a very contradictory problem? 

Only after enlightenment can one gradually transform the basis toward the pure emptiness (śūnyatā) of the tathāgatagarbha. Finally, when the first dhyāna arises and afflictions are eliminated, that is the most initial transformation of the basis. The second accomplishment of the transformation of the basis occurs at the stage of an eighth-bhūmi bodhisattva, and the ultimate accomplishment of the transformation of the basis occurs at the buddha stage. An ordinary being who has not attained enlightenment does not even touch upon the question of transforming the basis, let alone accomplishing it—there is no such thing. To accomplish the transformation of the basis, one must at the very least eliminate afflictions, so that one's mental disposition and wisdom both draw near to the tathāgatagarbha. The tathāgatagarbha has not the slightest ignorance or affliction, nor does any habitual tendency of affliction exist; therefore the sixth and seventh consciousnesses must rely on the tathāgatagarbha to purify their bodily, verbal, and mental actions and their wisdom, diligently cultivating precepts, meditation (samādhi), and wisdom. 

For the initial accomplishment of the transformation of the basis, one must at least eliminate afflictions and become a bodhisattva of the third or fourth fruit before it can barely be called an accomplishment of the transformation of the basis. But at that time habitual tendencies of affliction still remain, and one is still very far from the tathāgatagarbha; roughly two more incalculable eons of practice are needed to reach the stage of being beyond training (aśaikṣa) in the Great Vehicle, at which point one no longer needs to transform the basis toward the mental disposition and wisdom of the tathāgatagarbha. It is evident that the transformation of the basis is not something an ordinary being who has not attained enlightenment can accomplish—it can only be something to think about.