The 22 levels from earth to sky refer to the development of the Wish for Budhahood (Bodhichitta), from the initial intention in a baby Bodhisattva to the full Bodhichitta in the mind of a Buddha. This list of 22 comes from the Ornament of Realizations (Abhisamayalankara) by Arya Asanga which is one of the Five Great Books of Maitreya—The Future Buddha. They were taught by Maitreya to Arya Asanga in Maitreya’s heaven and then he brought them back to this world.
The 22 levels from earth to sky refer to the development of the Wish for Budhahood (Bodhichitta), from the initial intention in a baby Bodhisattva to the full Bodhichitta in the mind of a Buddha. This list of 22 comes from the Ornament of Realizations (Abhisamayalankara) by Arya Asanga which is one of the Five Great Books of Maitreya—The Future Buddha. They were taught by Maitreya to Arya Asanga in Maitreya’s heaven and then he brought them back to this world.
There are five stages or paths in the spiritual evolution of a human being. The second of those five paths is called The Path of Preparation, preparation here specifically refers to gaining an increasingly deeper intellectual understanding of emptiness which gives us the necessary spiritual power to have the direct perception of emptiness on path number three. This increasingly deeper understanding of emptiness progresses through four distinct stages while traversing the second path.