大乘起信論義疏 1.70

1.70

問曰：有法還滅可爾，太虛無法，云何更滅？答：以有對故，是無無滅耳。若理尋言以因感故，因力滅時終歸滅盡。感因物者有無齊等，豈無無滅。

Question: That existent dharmas return to cessation is permissible; the great void is a non-existent dharma, so how could it further cease? Answer: Because it is contrasted with existence, that non-existence is not without cessation. If in principle one investigates the words: because it is induced by causes, when the causal power ceases, it ultimately returns to complete cessation. The things that induce causes are equally existent and non-existent; how could non-existence not cease?