The Regulation of Life Activities by Manas

All changes, movements, and activities of the physical body fall within the scope of the formation aggregate (saṃskāra-skandha). They are directly regulated by the mental faculty (manas) and involve the body consciousness and mental consciousness, though not necessarily the analytical thinking or directive function of mental consciousness. The mental faculty clings to these activities as "self" and "what belongs to self," which constitutes the view of self (satkāya-dṛṣṭi).

Outward physical activities necessarily involve mental consciousness and body consciousness. For example, when walking along a familiar route section, the mental faculty can predominantly direct the mental consciousness and body consciousness to complete the journey without requiring analytical thinking or command from mental consciousness. If the route section is unfamiliar, the mental faculty must rely on the analytical guidance of mental consciousness to predominantly direct the mental consciousness and body consciousness to complete the journey.

However, the autonomic activities of the physical body, such as the functioning of internal organs, heartbeat, pulse, gastrointestinal peristalsis, cellular metabolism, nails growing, hair lengthening, changes in tissue structure, and the growth and changes of muscles and bones, etc., are not regulated by mental consciousness or the mental faculty. These changes occur according to karmic seeds and karmic causes. This is the sustaining activity performed by the Tathagatagarbha upon the living being, based on karmic seeds and causes.