大乘起信論義記 2.105

2.105

何以故者，責其立名。有二責意：一云、上開章中直云覺義，何故今結乃名本覺？二云、此中既稱本覺，何故上文直云覺耶？進退責也。釋云：以對始故，說之為本，答初意也。以始即同本者，以至心源時始覺即同本覺，無二相故。是故上文但云其覺，答後意也。良以本覺隨染生於始覺，還待此始覺方名本覺，故云本覺者對始說也。然此始覺是本覺所成，還契心源融同一體方名始覺，故云以始覺則同本也。

"Why is this?" challenges the establishment of the name. There are two intentions behind the challenge: first, in opening the section above, it directly said "the meaning of enlightenment"; why does it now conclude by calling it "innate enlightenment"? Second, since it is called "innate enlightenment" here, why did the text above directly say "enlightenment"? These are reciprocal challenges. The explanation says: because it is in contrast to the incipient, it is spoken of as the innate—this answers the first intention. "Because incipient is precisely identical to innate": when reaching the source of the mind, incipient enlightenment is precisely identical to innate enlightenment, having no two marks. Therefore, the text above merely said "enlightenment"—this answers the second intention. Truly, because innate enlightenment accords with defilement to produce incipient enlightenment, it must also await this incipient enlightenment before being named innate enlightenment; therefore it says that innate enlightenment is spoken of in contrast to the incipient. Yet this incipient enlightenment is formed by innate enlightenment, and only when it accords with the source of the mind and fuses into a single substance is it named incipient enlightenment; therefore it says: "because incipient enlightenment is precisely identical to innate."