4.3.4.辯因
辯因者，謂為成就所立宗義，依所引喻，同類、異類，現量、比量，及與正教，建立順益道理言論。
[解]什麼是建立宗旨的理由？就是爲了成就所建立宗旨的道理，而要說明它的理由，這就叫做因。依據所引的譬喻，有同類的譬喻，有異類的譬喻，有現量、比量和正教量的力量來支持，建立隨順、加強於因，成立道理的言論，這就是因。hetuḥ
katamaḥ yas tasyaiva pratijñārthasya siddhaye udāharaṇāśritaḥ
sārūpya- vairūpyato
vā pratyakṣato vānumānato vāptāgamato vā jāto yuktivādaḥ/
What
is the reason (hetu)? So as to prove the thesis-topic, it is whatever
declaration of principle (yuktivada), resorting to an example, that
is engendered by similarity and dissimilarity, or by direct
perception, or by inference, or by the lineage of the masters.
