大方廣圓覺修多羅了義經略疏 1.779

1.779

下餘五亦例此也。六皆名根者，識所依故、能發識故。前五各從自種生自現行，四大所造淨色為體。意根即第七識，由此攀外起意識故。

The remaining five below follow this pattern. All six are called 'faculties' because they are what consciousness relies upon and what can generate consciousness. The first five each produce their own active manifestations from their own seeds, taking the subtle form (rūpaprasāda) derived from the four great elements as their substance. The mental faculty is precisely the seventh consciousness, because relying on this to grasp external things, the mental consciousness arises.