十不二門指要鈔 2.74

2.74

初、明不二之由。已證者，蓋舉已證之位也。寂光、遮那依正不二，全由因德一念三千，儻因本不融，果何能一？縱修治令合，亦是無常，終歸分隔。

First, clarifying the reason for nonduality. "Having already realized" raises the stage of those who have already attained realization. That the environment and person of Quiescent Light and Vairocana are nondual derives entirely from the causal virtue of the three thousand realms in a single thought-moment. If they were fundamentally unintegrated in the cause, how could they be unified in the fruit? Even if cultivation were to bring them together, that would still be impermanent and ultimately return to separation.