瑜伽論記 18.97

18.97

諍訟究竟論者，謂諸外道因明者，景云：無出離意但求過非。新羅皛法師云：因明之興本始外道，理實通內。論主約本為語，故云外道因明論。陳那等論師欲伏外道，故造因明論，名為內論。今解：邪義因明名外因明，正義因明本是佛說寔以一切外論皆從教而流出也。

Regarding the treatise that reaches culmination in debate, this refers to the hetuvidyā of heterodox paths. Jing says: Having no intention of renunciation, they merely seek faults. Dharma Master Hyo of Silla says: The rise of hetuvidyā originally began with heterodox paths, but in reality it extends to the internal [Buddhist teachings]. The author of the treatise speaks in terms of its origin, and therefore calls it the hetuvidyā treatises of heterodox paths. Treatise masters such as Dignāga wished to subdue the heterodox paths, and therefore composed hetuvidyā treatises, calling them internal treatises. Now it is explained: Hetuvidyā of heterodox doctrines is called external hetuvidyā, while hetuvidyā of correct doctrines was originally taught by the Buddha, since in truth all external treatises flow out from his teaching.