The Process of Contemplative Practice Is the Process of Simultaneously Cultivating Samādhi and Prajñā.

What is contemplation? Contemplation is the observation and examination of dharmas, then making a judgment and arriving at a conclusion. If this process is complete, it begins with the mind consciousness starting to contemplate, gradually deepening, with the mind focused single-pointedly, and meditative concentration (samādhi) arises. Up to this point it is only a preliminary contemplation, relatively superficial and coarse. Even if a conclusion emerges, it is only the mind consciousness's coarse conclusion, not sufficiently refined; there is still doubt within the mind that has not been resolved—this is the doubt of the manas, meaning that the manas does not yet clearly understand or accept this conclusion. Contemplating further, the mind becomes increasingly focused, the meditative concentration grows ever deeper, the function exercised by the mind consciousness becomes smaller and smaller, while the manas's contemplative and deliberative function grows larger and larger. Finally, when the manas's wisdom is sufficient to make a judgment, a conclusion that is true and in accord with reality will be reached by the manas. Only then is doubt truly severed—this is realizing the dharma, the result of the mind consciousness and the manas cooperating in contemplation together. 

In the contemplative practice (vipaśyanā-caryā) of the four foundations of mindfulness, one first cultivates the contemplation of the body as impure. To contemplate the body, one must first begin with the breath. The specific method of contemplation is taught in the Buddhist sutras; as long as one honestly follows those contemplative steps one by one, one can observe the breath and the condition of the body faculty as they truly are. For example, when inhaling now, know where the air enters from when you inhale; observe that the air comes in through the nostrils, then passes through the nasal cavity into the lungs, and then into the dantian—this is roughly the process of inhalation. When exhaling, one should observe where the air travels from and to, where the air exits from, whether the breath is long or short, cold or warm, and what the body's sensations are—all of these must be observed clearly. When the mind is clear and lucid, one will know whether the breath is deep or shallow, long or short, where the breath has traveled, where it is blocked and not flowing, and how the breath is exhaled. This is contemplation, the preliminary stage in which the mind consciousness plays the leading role. 

In the process of contemplation, when the mind is focused single-pointedly, there is concentration, because all of one's energy is concentrated on observing the breath, no longer attending to or pondering other matters; with no scattered thoughts in the mind, the mind settles into concentration. After attaining concentration, one must also maintain contemplation, keeping an inner awareness of the breath; toward the dharma currently being contemplated, the mind must remain aware of it all. If one cannot clearly know it, this shows that the mind is scattered or has become drowsy. This knowing represents wisdom; with this knowing, the wisdom that eradicates the view of self (satkāya-dṛṣṭi) can gradually arise. 

At the same time as knowing, there is concentration; when the mind is very clear and lucid, there is wisdom—the equal cultivation of Samādhi and Prajñā, and the wisdom of emptiness will manifest. When one contemplates to a certain degree, one can recognize that the breath is subject to arising and ceasing, impermanent, and that the body is subject to arising and ceasing, impermanent—wisdom then arises. This is the wisdom of the manas; the mind consciousness's wisdom already knew long ago that the breath and the body are impermanent, subject to arising and ceasing—it knew this when studying the dharma—but that knowing does not play a decisive role. Only when one contemplates to the end can the manas's knowing play a decisive role; that is true wisdom. As long as the mind maintains this knowing, with prolonged practice and deepening effort, wisdom will arise, and one will be able to see the true reality of dharmas; this knowing, from the knowing of ignorance, becomes the knowing of enlightenment.