Only when morality, meditative concentration, and wisdom are fully complete can the "bottom of the bucket fall out."

In the past, Chan practitioners who investigated Chan and, upon finding the eighth consciousness, attained enlightenment would say that "the bottom of the bucket has dropped out." What is the bucket? In the Śūraṅgama Sūtra, the Buddha compared the human body to a flesh-bucket, shaped like a bucket. And sentient beings take this flesh-bucket to be themselves, to be a truly existing, imperishable self.

When a Chan practitioner awakens to the eighth consciousness, he knows that the eighth consciousness is real, never disappears, and is the true self; the five-aggregate body is merely a false shell manifested by the eighth consciousness, not real, not the self, yet also not different from the self that is the eighth consciousness. Thus he no longer takes the five aggregates as the self, negates the flesh-bucket of the five-aggregate body, and lays down the heavy burden of the five aggregates. At this point both body and mind are empty, and there is unsurpassed tranquility and ease—this is likened to the bottom of the bucket dropping out.

The prerequisites for the bottom of the bucket dropping out are: precepts, meditative concentration (samādhi), and wisdom must be complete; merit must be complete; the bodhisattva's six perfections must have been cultivated to completion; and the provisions for entering the Path must also be complete. Only when the conditions of time and circumstance ripen can the bottom of the bucket drop out. At this time one also simultaneously realizes the first fruit of the Small Vehicle, severs the three fetters, and will never again fall into the three evil destinies.

Because the first fruit of the Small Vehicle is the realization that the five aggregates and eighteen realms are suffering, empty, impermanent, and non-self, when one awakens to the eighth consciousness one also knows that the five aggregates and eighteen realms are not the self—they are illusory, empty and unreal, not real. Therefore, realizing the Great Vehicle fruit simultaneously realizes the Small Vehicle fruit, but realizing the Small Vehicle fruit does not necessarily mean one can realize the Great Vehicle fruit. This is the principle that the Great Vehicle dharma encompasses the Small Vehicle dharma.