Why can cultivating the contemplation of the skeleton eradicate the view of self and attain the fruits from the first to the fourth?

Since beginningless kalpas, ordinary sentient beings, due to ignorance and delusion, lacking meditative concentration and wisdom, can only observe and cognize the five aggregates and all dharmas in a rough manner, staying at the level of surface phenomena, unable to observe them in any substantive or ultimate sense. Therefore, they have always taken the physical body as a truly existent dharma, and have also taken the functions of the conscious mind as a truly existent dharma, not knowing their suffering, emptiness, impermanence, and non-self—this is a mistaken cognition of the five aggregates. Through cultivating the contemplation of the white skeleton (white-bone contemplation), one's meditative concentration grows ever deeper, and one's power of observation becomes ever stronger and ever more subtle, able to clearly observe the arising, ceasing, and transformation of the physical body. The truth of its emptiness will then surface, and the entire flesh of the physical body will appear in the form of a white skeleton; finally, even the white skeleton turns out to be empty. At this point, the view of the body and the view of self are eradicated.

The entire process of contemplative practice (vipaśyanā-caryā) takes place within a state of meditative absorption (samādhi). The skeletal features and the mark of emptiness of the physical body's bones and flesh are a realm of direct perception that arises naturally, not a realm of non-valid cognition imagined and deduced out of thin air by the mind consciousness. All meditative absorptions are initiated by the manas; they are all realms of the manas's direct-perception wisdom-cognition, containing not the slightest component of the mind consciousness's inference or non-valid cognition. Within meditative absorption, the mind consciousness can only know passively, moving and knowing in accordance with the manas. Before entering meditative absorption, the mind consciousness can engage in active thinking and observation, guiding the manas onto the path; thereafter, meditative concentration will deepen more and more, and the initial concentration-realm meditative absorption will appear. The mind consciousness's power of agency grows ever smaller, while the manas's process of deliberation (manasikāra/manana) grows ever greater. When the manas truly sees the dharma as it is, wisdom manifests, and the meditative absorption of the equal cultivation of Samādhi and Prajñā appears before one—at this point one realizes the fruit.

Without meditative concentration, the manas cannot attain focused attention upon the physical body and the five aggregates, cannot deliberate and see the dharma as it truly is, and does not know the true appearance of the physical body and the five aggregates; thus wisdom cannot arise. The white-bone contemplation can give rise to meditative concentration, and meditative concentration in turn draws forth wisdom; ultimately one eradicates the view of self and realizes the fruit. The white skeleton, which at first seemed impossible, finally appears in the mind—this is the form produced by concentration (dhyāna-rūpa). Seeing the white skeleton as the form produced by concentration, one knows the physical body is not the self; the meditative absorption of the equal cultivation of Samādhi and Prajñā appears, the pure dharma eye arises, and one realizes the fruit.