大方廣圓覺修多羅了義經略疏 1.783

1.783

The above have all been explained. However, the reason why the seventh consciousness is not mentioned among the eight consciousnesses is that its meaning corresponds to the dust of seeing, hearing, and the rest. By combining the seventh with the eighth, it is called the dust of seeing, etc. Thus the Yogācārabhūmi says: 'When the ālayavijñāna arises, it necessarily corresponds with two consciousnesses.' Furthermore, combining the seventh with the sixth, it is called the dust of seeing, etc., because when the mental consciousness conditions external objects, it must internally rely on the manas as its defiled faculty before it can arise. Hence the treatise quoted above says: 'Relying precisely on this continuous consciousness, down to being named the manovijñāna.' There is no separate manas listed in that treatise or in this sūtra, and the Laṅkāvatāra is also like this; this is because the seventh calculates the internal as self, combining with the transforming mark, and calculates the external as what belongs to self, combining with the consciousness of things. If one did not connect the preceding and bring along the succeeding, then the meaning of showing the mental factors arising in succession would not be apt.