俱舍論頌疏論本 28.17

28.17

非想非非想，昧劣故立名者，立第四名，由想昧劣，謂無下地明慧勝想，得非想名；有昧劣想，名非非想，故約彼處想昧劣故，當體立名，名非非想。前三無色約加行立，第四非想約當體立。

Regarding "Neither-perception-nor-non-perception is named because [perception] is faint and inferior": the fourth name is established because perception is faint and inferior. Because it lacks the clear, luminous, and superior perception of the lower levels, it receives the name "neither-perception"; because it possesses a faint and inferior perception, it is called "nor-non-perception." Therefore, with respect to the faintness and inferiority of perception in that sphere, the name is established according to its own nature, called "neither-perception-nor-non-perception." The former three formless [spheres] are established with respect to preparation; the fourth, neither-perception[-nor-non-perception], is established with respect to its own nature.