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

The beings in the Formless Realm have no physical body but possess consciousness. Where there is consciousness, there exists the skandha of consciousness. Although they have consciousness, they cannot hear the Dharma, much less contemplate it. Without a physical body, they are not humans but celestial beings in the heavens, a higher form of life. Sensation, perception, mental formations—the five universal mental factors—are all present in the eight consciousnesses. The beings in the Formless Realm also possess the sensation, perception, and mental formations of consciousness, as well as those of the mental faculty (manas), and even those of the eighth consciousness (ālaya-vijñāna).

The Buddha can preach the Dharma to the beings in the Formless Heaven, but those in the Form Realm cannot hear it, nor can humans, ghosts, or spirits. The beings in the Formless Realm are few in number, mostly adherents of non-Buddhist paths, constantly abiding in samadhi. Thus, there is no need to preach to them. Moreover, even within the second dhyana, one cannot hear the Dharma, how much less in the dhyanas beyond the fourth, where it is even more impossible to hear or contemplate the Dharma. Therefore, the Buddha does not go to the Formless Heaven to preach.

One can enter the second dhyana in an instant and then become unaware of everything. Emerging from samadhi also happens in an instant, and only upon emerging does one realize they had been in samadhi. They feel their body is extremely comfortable, their mood especially joyful, and their mind exceptionally clear. A faint sound is enough to awaken the ear consciousness, causing them to emerge from samadhi. Because the mental faculty still has matters it dwells upon, when the time comes, if someone reminds them of something important—even the sound of a mosquito—they can hear it and thus emerge from samadhi. Before entering samadhi, amidst very noisy sounds, the mind can quickly settle into stillness. The clamor gradually fades until it becomes inaudible, and then one enters samadhi.

The Buddha preached the Avatamsaka Sutra and the Kṣitigarbha Sutra in the Desire Heaven and the Form Heaven, after which they spread to the human realm. All other sutras were preached in the human realm, allowing celestial beings to descend and listen, while ghosts, spirits, and animals could also hear the Dharma, thereby benefiting a vast number of sentient beings.