成唯識論述記 5.957

5.957

述曰：汝設若以身識等定相續，以苦根為第八者，如憂間斷何處定成？又若爾者，彼更憂根何須間斷？更無別義，意識間斷，五識相續故。又意無捨受，非易起受故。今解此中有苦師意，必定無憂，以苦為不定。意中苦受即約容受，許亦間斷。

The Commentary states: If you suppose that the tactile consciousness and so forth are definitely continuous, taking the faculty of pain as the eighth: just as sorrow is interrupted, where would it be definitely possessed? Furthermore, if that were so, why should their faculty of sorrow be interrupted? There is no other reason than that the mental consciousness is interrupted while the five consciousnesses are continuous. Moreover, the mind lacks the sensation of equanimity, because it is not an easily aroused sensation. Now, explaining the intention of the master here who maintains there is pain: there is definitely no sorrow, and pain is regarded as indeterminate. Painful sensations in the mind are explained in terms of circumstantial sensations, allowing that they are also interrupted.