The Problem with Epistemology
You can easily find well-respected sources on the Internet offering definitions of this philosophical branch of inquiry. Wikipedia’s is here; its content is compatible with most definitions I have encountered.
It seems to me that there is a very serious problem there.
It is possible to assume a premise, or a method, in order to disprove it – usually by showing that assuming it leads to a contradiction. But it is useless to assume something while trying to support it.
So then how, exactly, is it possible to investigate the concepts of knowledge and justification? You’d have to already possess the standards that you’re supposedly asking about in order to proceed. Without a method of evaluating an assertion as true or false, or already-existing ideas about how a conclusion is justified, you can’t evaluate or conclude anything.
At most, then, all epistemology can be is a way to make implicitly-accepted standards explicit. Once they’re explicit, there’s nothing more that can be done.