成唯識論述記 7.55

7.55

述曰：自下第三解「二各二」。尋、伺後說故，行相同故。尋、伺初二，染、淨後二，文易可知。

The Commentary states: From here down is the third section explaining 'the two are each twofold'. Because investigation and evaluation are stated last, and because their mental aspects are similar: investigation and evaluation constitute the first 'two', and defiled and pure constitute the latter 'two'; the text is easy to understand.