成唯識論述記 5.329

5.329

述曰：下會違也。釋無惛沈、掉舉所以。行相相違，起一無一，非諸染心皆能遍起。掉舉外相高生，惛沈內相下起。

The Commentary states: Below is the resolution of apparent contradiction, explaining the reason why lethargy and restlessness are absent. Because their modes of activity are mutually opposed, when one arises the other does not; they cannot both arise universally in all defiled minds. Restlessness is high-rising with an external mark, while lethargy is downward-directed with an internal mark.