Reason Dumbledore trusted Snape

[va32h]

No: HPFGUIDX 171733

Pippin:
 
But where do we see this in canon? He's proud of his magical ability,
but Hermione's proud of hers too, and that doesn't stop her from 
feeling dreadfully insecure. Snape's brilliance just made him a 
potions nerd -- and there's no sign anybody but Slughorn ever cared 
about that. His prowess at curses doesn't seem to have made him 
special either. He was just, as Sirius said, that greasy little 
oddball who was good at dark arts. 

va32h:

Where do we see secretly-thinks-he-deserves the Marauders' abuse in 
canon either? At least I don't. 

Looking at Snape as a teacher suggest to me how he feels about 
learning magic. He is frustrated with Hermione, because in class, she 
only follows directions and quotes textbooks. He is frustrated with 
Neville, because Neville does have the ability, he just lacks the 
confidence, and aside from being predisposed to loathe Harry - Harry 
is a wizard with innate talent, but he is lazy and undisciplined. 

These are all in direct contrast to himself, who showed initiative, 
confidence in his skills as a potioneer at least, and a great deal of 
self-discipline. 

I also found it telling that at the end of HBP, when Snape reveals 
himself to be the Prince, what sets him off is Harry using one of 
Snape's own spells, just like his father did. That seems to affront 
Snape the most - not that Harry or even James would attack him, but 
that both were too darn lazy to come up with their own curse with 
which to do it. 

Pippin:
I agree with this, but if Snape only became disillusioned with the 
leader, not the cause, then why go to work for someone as zealously 
against the cause as Dumbledore? After all, Voldemort had lots of 
enemies among people like the Blacks who agreed with his goals but 
were revolted by his methods. 

va32h:

Well, in the first place, I don't think Snape ever supported "the 
cause" - that's my point. He didn't join the DE because he secretly 
loathed the Muggle parts of himself. He was bamboozled by Voldemort. 

And if Snape discovered Voldemort had tricked him into signing up for 
a lifetime of service, he wouldn't be "disillusioned", he'd be 
furious. But Snape being as self-disciplined as he is wouldn't do 
something impetuous like Regulus Black - a bold move against 
Voldemort just gets yourself killed. 

Snape's style would be - as it was when he punished Neville by having 
him sort toad innards and punished Harry by making him copy out the 
misdeeds of his father and godfather - to get revenge in a 
particularly cutting and personal way. 

So if Voldemort used Snape's personal history to fool him - what 
better way to get revenge than by fooling Voldemort - and going to 
work for Voldemort's greatest personal enemy, Albus Dumbledore. Sure, 
the Blacks were Voldemort's enemies, and the Ministry would naturally 
be opposing Voldemort. But Voldemort has a particular, personal 
grudge against Dumbledore. Which makes him the perfect person for 
Snape to "cheat" with, if he wants to achieve maximum revenge. 

va32h