Can What Others Tell Me Count as Knowledge?

If a station employee says that a train has been moved to platform three, and you go there and board it, we would ordinarily say that you knew where the train was, even though you never saw the scheduling record. Much of what we know about history, geography and daily events comes from other people. If knowledge required first-hand verification, our knowledge would be remarkably sparse.

The dispute concerns what gives testimony its authority. A Humean reductionist tradition stresses that experience must support our judgement that speakers are reliable, reducing testimonial justification to observation, memory and inference. Thomas Reid instead argued that people have natural dispositions both to speak truthfully and to trust others. If reliability had to be independently proved before every exchange, language learning and social knowledge could barely begin. Contemporary epistemology still asks whether testimony is a basic source of justification or merely transmits reasons already possessed by the speaker.

My view is that ordinary testimony can yield knowledge, but its default credibility must remain open to defeat by the circumstances. A uniformed station employee announcing a platform change through the public-address system is supported by role, channel and signs that can be checked. A stranger casually pointing through a noisy crowd provides less. The listener need not redo the railway's scheduling work, but should notice whether the speaker was in a position to know, might be misleading them, or is contradicted by the display board. Trust does not abandon judgement; it locates judgement within the real conditions through which knowledge moves between people.

https://plato.stanford.edu/entries/testimony-episprob/