The formless attainments
Four ultra-refined states of consciousness reached when the meditating mind lets go even of all sense of shape.
Deep concentration meditation in Buddhism is mapped as a ladder of increasingly subtle states. The formless attainments (Pali arūpa-samāpatti, "formless attainments") sit at the very top of that ladder — four refined meditative states in which the mind has let go not only of the body and the senses but even of any sense of shape, location, or material form altogether. They are reached only after the four "form" absorptions (jhāna) have been mastered.
The four, each entered by releasing the object of the one before, are: (1) the base of infinite space (ākāsānañcāyatana) — attention dwelling on boundless space with no objects in it; (2) the base of infinite consciousness (viññāṇañcāyatana) — turning to the limitless awareness that was perceiving that space; (3) the base of nothingness (ākiñcaññāyatana) — resting in the quiet recognition that there is "nothing there" to grasp; and (4) the base of neither-perception-nor-non-perception (nevasaññā-nāsaññāyatana) — a state so still that perception is barely flickering, neither clearly present nor clearly absent.
It is important to be accurate here: in Buddhism these exalted states are not the goal. They are extraordinarily peaceful and were known to Indian meditators before the Buddha — tradition holds that he learned the last two from his early teachers Āḷāra Kālāma and Uddaka Rāmaputta — but they are still conditioned, temporary, and within the round of rebirth. The Buddha is said to have mastered them, found they did not end suffering, and gone beyond them. Liberating insight (wisdom into impermanence and non-self), not depth of trance alone, is what frees the mind. The formless states are powerful tools for steadiness, prized but not mistaken for the destination.