Majjhima Nikāya - Mūlapaṇṇāsa Pāḷi - Mūlapariyāya Vagga. The Buddha explained the basis of all phenomena, specifying twenty-four categories such as the four elements (earth, water, fire, wind); sentient beings, devas; the seen, the heard, the thought of, the known; the oneness, the multiplicity, the whole; and the reality of Nibbāna.Only the enlightened ones can see them in true perspective.