Why Did the Buddha Not Go to the Formless Realm to Teach the Dharma

Celestial beings in the Formless Realm possess no physical body but have consciousness. Where there is consciousness, there exists the skandha of consciousness. Although they have consciousness, they cannot hear the Dharma, much less contemplate it. Having no physical body does not make them humans among men, but rather celestial beings in the heavens—higher forms of life. The aggregates of sensation, perception, and mental formations, along with the five universal mental factors, are all present in the eight consciousnesses. Celestial beings in the Formless Realm also experience the sensations, perceptions, and mental formations of consciousness, as well as those of the mind faculty (manas), and those of the eighth consciousness (ālaya-vijñāna).

The Buddha can preach the Dharma to celestial beings in the Formless Realm, but those in the Form Realm cannot hear it, nor can humans in the human realm, ghosts, or spirits. The number of beings in the Formless Realm is exceedingly small, and they are all adherents of heterodox paths, perpetually absorbed in meditative concentration. Thus, there is fundamentally no need to preach the Dharma to them. Moreover, from another perspective, the Dharma cannot be heard even within the second dhyāna, let alone within meditative states beyond the fourth dhyāna, where hearing and contemplating the Dharma becomes even more impossible. Therefore, the Buddha does not go to the Formless Realm to preach the Dharma.

The second dhyāna can be entered instantaneously, after which one becomes unaware of everything. Exiting the concentration is also instantaneous; only upon emerging does one realize they were just absorbed, feeling extreme physical comfort, exceptional mental joy, and remarkable clarity of mind. A faint sound is sufficient to awaken the auditory consciousness, causing one to exit the concentration. Because the mind faculty still holds onto matters of concern, when the time comes and an important matter is brought to attention—even by something as slight as a mosquito's buzz—it can be heard, prompting an exit from concentration. Before entering concentration, amidst very noisy sounds, the mind can quickly settle into stillness. The clamor gradually fades into faintness until it becomes inaudible, and then one enters concentration.

The Buddha preached the Avataṃsaka Sūtra and the Kṣitigarbha Sūtra in the Desire Realm and the Form Realm heavens, after which they spread to the human realm. All other sūtras were preached in the human realm, enabling celestial beings to descend and listen, while ghosts, spirits, and animals could also hear the Dharma. This way, far more sentient beings could be delivered.