成唯識論述記 5.621

5.621

述曰：此舉有法及舉因成。意識者，是有法；因云六識中攝，言在中攝，不言六識攝，是一識攝故；喻如五識，此皆舉之。

The Commentary states: This adduces the subject (dharmin) and adduces the reason (hetu) to establish it. 'Mental consciousness' is the subject; the reason states 'being subsumed among the six consciousnesses'—it says 'subsumed among' and not 'subsumed under the six consciousnesses', because it is subsumed under one consciousness; the analogy is 'like the five consciousnesses'; all these are adduced.