大乘起信論廣釋卷第三．四．五 3.72

3.72

論。名為意識至分別事識　釋曰。此製立其名也。既緣六塵應名六識。而今就其一意識義故不別出眼等五識。故涅槃云。譬如一識分別說六。金光明經。心如幻化馳駛六塵而常妄起分別諸法。故緣六塵但名意識。即此意識依於六根別取六塵。故名分離。又能分別知來內外善惡因果種種事相故。復說名分別事識。

[Treatise:] It is named mental consciousness [...] discriminating phenomenal consciousness. [Commentary:] This establishes its name. Since it conditions the six sense-objects, it should be named the six consciousnesses; but here, with respect to its sense as a single mental consciousness, the five consciousnesses of the eye and so on are not separately brought out. Thus the Nirvāṇa [Sūtra] says: "Like a single consciousness, it is discriminately called six." The Suvarṇaprabhāsa Sūtra says: "The mind is like an illusion, galloping through the six sense-objects, constantly falsely generating discrimination of all dharmas." Therefore, conditioning the six sense-objects is merely named mental consciousness. This very mental consciousness relies on the six sense-faculties to separately grasp the six sense-objects, hence it is called "separative." Furthermore, because it can discriminatively know coming and going, internal and external, good and evil, causes and effects, and various phenomenal characteristics, it is also called "discriminating phenomenal consciousness."