Threefold means of valid knowledge

Tats_21

[Base sūtra:] The means of valid knowledge (pramāṇa) is threefold.

Tats_21.c1

[Verse:] The seen [perception], inference, and the word of a trustworthy person—this is [the threefold] means of valid knowledge. The five sense-organs [yield] perception; but [the inference of] rain [is made] by the rising of clouds—

Tats_21.c2

[Verse:] [this is] inference. "Indra [is] the king of the gods"—[such] verbal [testimony] is the means of cognition [i.e. trustworthy word].

Tats_21.c3

And in scripture (āgama) too: "Released from his own works, free of passion and hatred, possessed of knowledge, endowed with [good] conduct—such a one is to be known [as a trustworthy authority], and [the object] to be known is of like [trustworthiness]."