The thirty-one planes read from bottom to top as a moral thermometer. Four planes of loss occupy the base: the hells, where beings burn off the results of hatred; the animal realm, of delusion; the hungry ghosts, of greed, wandering with vast bellies and needle throats; and the asuras, consumed by envy and endless war. The fifth plane is the human world, and the tradition's estimate of it is precise: rare, precious and optimal, painful enough to motivate practice and free enough to permit it, which no heaven is. Above rise the six sense-sphere heavens, from the realm of the Four Great Kings through Trayastrimsa, Yama's heaven, Tushita, the heaven of delight in creation, up to that of the gods who control others' creations.
All of this, hells to high heavens, is still the desire realm, and rebirth within it is driven by ordinary merit and demerit: generosity and virtue lift, cruelty and craving sink. Only meditation moves a being higher, into the sixteen form-realm heavens matched to the four absorptions, among them the five Pure Abodes where non-returners complete the path, and at the summit the four formless planes. The architecture teaches its own lesson: goodness alone reaches only the middle of the building, concentration reaches the top of it, and nothing within the building lasts. The Buddha's path, the tradition insists, is not a stairway to the thirty-first floor but the exit.