Why is Snape trusted? Ok, Dumbledore had incontrovertible proof, but no one else did. The constant refrain, as expressed most eloquently by Lupin in the sixth book is that Dumbledore trusts Snape and we trust Dumbledore. Now Lupin clearly admits to not knowing why Dumbledore trusts Snape. Why does he assume that Dumbledore is practically infallible? Well maybe because Dumbledore is the greatest wizard alive so it is a safe assumption that Snape wouldn’t be able to fool him. Yet Voldemort is pretty much Dumbledore’s equal and he also trusts Snape. ?? ????, Snape is fooling one of the two greatest wizards. So why should anyone be so confident that Dumbledore is not the one being fooled. (If anything I would think that between Dumbledore and Voldemort, Dumbledore is more likely to place trust in someone who shouldn’t really be trusted.)
I have a few possible answers:
1) Voldemort didn’t really trust Snape. However, I don’t see how Lupin could have known this.
2) Dumbledore might have told Lupin that he had incontrovertible proof without telling him what the proof was.
3) Something to do with how Voldemort doesn’t understand love and those kind of things.