大乘起信論義疏 1.5

1.5

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.