Only with the perfection of meditative concentration (dhyāna and samādhi) is realization possible

The so-called contemplative practice (vipaśyanā-caryā), before it is realized, is called deliberation and investigation—it is deep and subtle deliberation, exploration, probing, searching, and sustained examination (vicāra), not shallow mental activity; it must rest in the manas. After realization, it is called observation—directly observing, in the present, the various operations of the tathāgatagarbha within the body of the five aggregates (pañcaskandha), observing the mysteries of all dharmas; even then, there must still be deeper and subtler deliberation and investigation, all of which must rest in the manas. Contemplative practice both before and after realization must take place in preparatory concentration (anāgamya-samādhi) or in the concentration of the first dhyāna. Without meditative concentration, it is merely learning, understanding, and reasoning done purely by the mind consciousness, and the deliberation is very shallow. Even with meditative concentration, if the concentration is relatively shallow, the power of deliberation is also insufficient, remaining only within the mind consciousness, and enlightenment cannot be realized. The contemplative practice of the Four Noble Truths, the contemplative practice of realizing the tathāgatagarbha, the illusion-like contemplation, the mirage contemplation, the dream-like contemplation, and the mirror-like contemplation—these contemplative wisdoms progress layer by layer, with the wisdom of contemplative practice becoming ever deeper and subtler.

The so-called enlightenment must be the mind consciousness and the manas personally realizing the tathāgatagarbha; merely understanding the principle of the tathāgatagarbha is not enlightenment. Those principles can be known through various channels, but realizing the tathāgatagarbha must be accomplished through Chan investigation and personal realization. Enlightenment is not knowledge and principles learned from others, but what the manas personally realizes through effective investigation.