Only when self-grasping is completely eradicated can one attain Buddhahood.

After attaining the first fruit and eradicating the view of self (satkāya-dṛṣṭi-prahāṇa), one continues to cultivate and deepen contemplative practice (vipaśyanā-caryā) on the illusory nature of the five aggregates (pañca-skandha) and the eighteen realms, gradually beginning to sever self-grasping. But self-grasping is even harder to sever; this is why a person of the first fruit must undergo seven rounds of rebirth in the heavens and seven rounds in the human realm, cultivating back and forth, before finally becoming an arhat of the fourth fruit. Do the math: seven times in the heavens and seven times in the human realm—add them together and see how much time that amounts to. Once you calculate it, you will understand how difficult it is to sever self-grasping—infinitely more difficult than eradicating the view of self.

What is self-grasping? It is the manas's clinging attachment to the five aggregates as "self," unwilling to let go. Why does it still cling? Because the view of self regarding the five aggregates has not been eradicated thoroughly; in certain aspects and to a certain degree, it still takes certain functions and operations of the five aggregates as itself, and clings to them without letting go. Since beginningless kalpas, the habit energy of grasping at self has been too deep, ignorance too heavy, and craving for the three realms too difficult to uproot—that is why such a long time is needed to sever the afflictions of self-grasping. If the manas could eradicate the view of self regarding the five aggregates thoroughly in one stroke, its self-grasping would be severed completely at the same time, and that person would be a great arhat of the fourth fruit. And one who truly severs the manas's grasping at self completely becomes a Buddha directly—not merely a great arhat of the fourth fruit who is liberated in both ways. Thus the self-grasping of arhats and pratyekabuddhas has not been severed thoroughly and exhaustively, which is why they cannot yet become Buddhas.

Why does the eighth consciousness not need to eradicate the view of self? He has no view of self, so He does not need to eradicate it; only one who has a view of self needs to eradicate the view of self.