What Is the Mechanism Behind the Sensation of Pain?

When awareness of pain arises, four consciousnesses are operating: the body consciousness, the mind consciousness, the manas, and the eighth consciousness. Only when these four consciousnesses work in harmony can the pain in the foot be perceived; lacking even one, it cannot be accomplished. Specifically, it is the body consciousness and the mind consciousness that feel the pain, while the manas and the eighth consciousness do not feel pain. How can these four consciousnesses be distinguished from one another? If one can distinguish them, one possesses great wisdom.

The sensation of feeling pain belongs to the aggregate of feeling (vedanā). Only when the aggregate of feeling is exhausted can one cease to feel pain. To cultivate to the point of exhausting the aggregate of feeling, one must be at the fourth dhyāna or above; and after seeing one's true mind and awakening to one's nature, one must reach the level of a fourth-bhūmi bodhisattva or above. Master Xuanzang's Indian Yogācāra teacher still suffered from headaches so severe that he wanted to leave, and Avalokiteśvara Bodhisattva came to stop him, telling him to first finish teaching Xuanzang the Yogācāra teachings, and also revealing to him the karmic causes and conditions from his past lives. Are there any people in the world today who have cultivated to the level of wisdom of Xuanzang's Indian teacher? Even if they had, they still would not have exhausted the aggregate of feeling, and perhaps not even exhausted the aggregate of form (rūpa)—so what is there to say about having no sensation of pain?

As for people without the sensation of pain: one kind is born with it as a retributive result, which disappears when their merit is exhausted. Another kind receives it as a blessing bestowed by beings of other realms, which is even more impermanent and unreliable. Yet another kind attains it through cultivating the four dhyānas and eight samādhis, which is also a conditioned dharma of arising and ceasing. But bodhisattvas at the fourth bhūmi and above can sustain it; those who are not noble ones who have seen their true mind, awakened to their nature, and realized the fruits simply cannot maintain it.