With oral and written testimony, humans cannot transmit knowledge

of the Sun and the Earth,or about your own family history,or about what goes on in the minds of other humans.Instead, these beliefs are mostly based on what you've been told.Without spoken and written testimonies,human beings could not pass on knowledge
from one person to another,let alone from one generation to another.We would know much, much less about the world around us.So learning about a topic by asking an expert on that topic,
or appealing to authority,helps us gain knowledge,but, it doesn't always.