成唯識論述記 1.189

1.189

述曰：由內識體是依他故，必依種子因緣所生，非體是無，如遍計境。彼實我、法猶如龜毛，識依他有，故非彼類，即顯內識是依他有，心外實境體性都無。此中色等相、見二分內識所變，不離識故，總名內識。由此真如是識性故，亦非非有。

The Commentary states: Because the substance of internal consciousness is dependent, it must depend on seeds and causal conditions to arise; its substance is not nonexistent like imagined objects. That real self and real dharmas are like the hairs of a tortoise; consciousness exists dependently, and is therefore not of that kind. This reveals that internal consciousness exists dependently, while the substantial nature of real objects external to the mind is entirely nonexistent. Here, the two parts—nimittabhāga and darśanabhāga—of matter and so forth are transformed by internal consciousness and are not separate from consciousness, and hence are collectively called "internal consciousness". Because of this, tathatā, being the nature of consciousness, is also not nonexistent.