[499] Which phenomena (dhammā) are indeterminate (abyākata)?
On the occasion when one develops jhāna of the formless sphere (arūpāvacara) that is functional (kiriya) — neither wholesome nor unwholesome, and not the result of kamma (kammavipāka), but a pleasant abiding in the present life (diṭṭhadhammasukhavihāra) — when, with the complete transcending of the sphere of nothingness (ākiñcaññāyatana), with the abandoning of pleasure … one enters upon and dwells in the fourth jhāna accompanied by the perception of the sphere of neither perception nor non-perception (nevasaññānāsaññāyatana): on that occasion there is contact (phassa) … there is non-distraction (avikkhepa) … These phenomena are indeterminate.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.