Hiriyanna explains Sabda-pramana as a concept which means reliable expert testimony. The schools of Hinduism which consider it epistemically valid suggest that a human being needs to know numerous facts, and with the limited time and energy available, he can learn only a fraction of those facts and truths directly.
Hiriyanna explains Sabda-pramana as a concept that signifies authoritative expert testimony. The Hindu schools that consider it valid propose that humans require extensive knowledge, but due to the constraints of time and energy, they can only acquire a portion of that knowledge through direct perception.