釋氏要覽 2.336

2.336

婆沙云。無色可了施設故名無色。有四天。謂空處。識處。無所有處。非想非非想處（婆沙論。問。何故世尊。於四無色立處名。答為破外道執空處為無身涅槃。執識處為無邊意涅槃。執無所有處名淨聚涅槃。執非想非非想處。名世間空窣堵波涅槃。佛說為生處。非真解脫故）。

The Vibhāṣā states: "Because there is no form to be cognized and posited, it is called formless." It has four heavens: namely, the Stage of Boundless Space, the Stage of Boundless Consciousness, the Stage of Nothingness, and the Stage of Neither-Thought-Nor-Non-Thought. (The Vibhāṣā-śāstra asks: "Why did the World-Honoured One establish the name of 'stage' [āyatana] for the four formless [realms]?" It answers: "In order to refute the heterodox views that cling to the Stage of Space as a 'nirvāṇa without a body', cling to the Stage of Consciousness as a 'nirvāṇa of boundless mind', cling to the Stage of Nothingness under the name 'pure mass nirvāṇa', and cling to the Stage of Neither-Thought-Nor-Non-Thought under the name 'worldly empty stūpa nirvāṇa'. The Buddha preached them as places of rebirth, not as true liberation.")