因明入正理論疏 2.162

2.162

述曰：下第四，釋異分同全，有二，此初標名舉宗、因。謂聲顯論對聲生立：是勤勇無間所發宗，無常性因。

Commentary: The following is the fourth [variety of inconclusive reason], explaining [the reason that] occurs in a part of the heterologue and throughout the homologue. It has two parts; this first sets forth the name and presents the thesis and the reason. It refers to the Śabdābhivyaktivāda asserting against the Śabdakāryavāda the thesis, "[Sound] is produced by effort," with the reason, "because it is impermanent."