The āstika-darśanas or systems of Indian philosophy that accept the autho-rity of the Vedas, have given the highest place to śabda-pramāṇa (scriptural testimony), also called āgama (authentic word handed down by tradition) and āpta-vākya (statement of a trustworthy person).
It is impossible to obtain all know-ledge through direct perception since the range of the organs of perception is limited. Nor can inference be of much help since it is based on previous experiences which again are based on direct perception. At some stage, faith in the word, spoken or heard or read, has got to be resorted to. In fact the knowledge gained thus is enormous. Even the day-to-day life becomes impossible without believing in the authenticity of the spoken or written word.
Of course, it goes without saying that the person through whom such knowledge comes, must be trustworthy and that he should have based his findings on authentic experience or sources.
Coming to things divine, since they pertain to areas of supersensuous experience, only persons of the highest spiritual calibre—ṛṣis as they are called—can be the guides and the mentors. The scriptures, which are revelations handed down through them, are the highest class of āpta-vākya literature.
See also PRAMĀṆAS.