大乘起信論義疏 1.5

1.5

所言「論」者，簡異佛經之辭也。若通言之，一切皆論，謂五明論是也；一切皆經，謂五經是也。若別言之，佛所說者，名之為經；若餘人說、佛所印可，亦名為經，如《維摩》、《勝鬘》等是也。若佛滅度後，聖人自造解釋佛經，名之為論，凡夫所造名為義章。今此論者，佛滅度後，菩薩所造，名之為論。論者，所謂賓主相談，因之為論，故言「大乘起信論」也。

As for what is called "treatise" (śāstra): it is a term that distinguishes it from the Buddha's sūtras. Speaking generally, everything is a treatise, as in the treatises of the five sciences; everything is a classic, as in the five classics. Speaking specifically, what the Buddha spoke is named a sūtra; what another person spoke and the Buddha endorsed is also named a sūtra, as with the Vimalakīrti, the Śrīmālā, and so forth. If, after the Buddha's parinirvāṇa, sages themselves compose works to explain the Buddha's sūtras, they are named treatises; what ordinary people compose are named expository essays. Now this treatise was composed by a bodhisattva after the Buddha's parinirvāṇa, so it is named a treatise. A treatise is where host and guest engage in dialogue, and because of this it is a treatise; therefore it is called the Awakening of Faith in the Mahāyāna.