No, you don’t have to understand why someone believes something to believe justified that they are justified in believing it. All I need is to believe justifiably that they’re generally a good judge of facts in this domain. To hold otherwise would be an extremely unreasonable standard that would prevent me from ever learning pretty much anything. Whereas in fact, I’m perfectly justified in believing in, say, the existence of Argentina, even though I’ve never observed it myself.
No, you don’t have to understand why someone believes something to believe justified that they are justified in believing it. All I need is to believe justifiably that they’re generally a good judge of facts in this domain. To hold otherwise would be an extremely unreasonable standard that would prevent me from ever learning pretty much anything. Whereas in fact, I’m perfectly justified in believing in, say, the existence of Argentina, even though I’ve never observed it myself.