Get yer piping hot Snape Theory right here...

[Sydney]

No: HPFGUIDX 84770

I'd thought I'd float this theory over here, it's been noodling 
around my head for a while.  

(sorry this isn't in Theory Bay format, I get exhausted just READING 
those brilliantly crafted posts!  I might throw in some boat 
metaphors though:) )

If there was one thing that really took me aback in OoP, it was 
this:  that Snape really DID want the DADA job, in fact applied for 
it every year, and that Dumbledore kept turning him down.  I had 
been cozily confident that the rumour was just that, a rumour, and 
at some point someone would say, "Goodness, where did you get that 
idea?  Dumbledore BEGS Snape to teach DADA, and he won't do it."  
Mostly due to the way that the information was presented, as casual 
gossip by Percy of all people, I'd have thought you'd have to pry 
Snape out of his beloved Potions dungeon with a crowbar.

So now I've been sitting in my rapidly-flooding deinflated dingy, 
casting about for a new craft to stay afloat in (Syd eyes her 
metaphor dubiously, but presses on).

I listened avidly to the webcast of the Albert Hall reading, and 
found the answer to the question, "Why won't D-dore let Snape teach 
DADA" intriguing and puzzling.  JKR hemmed and hawed, then said it 
would be a spoiler, then said that Dumbledore feared it would bring 
out the worst in Snape, so he started him in Potions to see how he 
got on.

Now the most obvious and simple explanation is the 'recovering 
alcoholic' one, that Dumbledore fears that if Snape taught DADA 
classes, that he would regain his taste for Evil and, well, go nuts 
or whatever.  Or that he would abuse his students with hexes or some 
such thing.

Like any obvious and simple explanation, this doesn't actually work 
very well.  First off, why would that be a spoiler?  Everyone knows 
Snape is a bit of an evil bastard.  Anyhow, it's DEFENSE against the 
Dark Arts.  The main temptation Snape would be faced with it seems, 
it textbooks on Hinkypunks.  If Dumbledore is worried about the 
students safety, isn't letting Snape mess around with poisons and 
mind-altering potions with them kind of on the same level?  And how 
could Snape possibly be worse than Umbrige or Lockhart?

But mostly, it's this:  "I trust Severus Snape" is simply 
imcompatible with "But I'm worried that if I let him near 
a 'Ridiculus' spell, he'll freak out and rejoin Voldemort."  

Whatever Snape is doing right now for the Order, it MUST involve 
exposure to the Dark Arts.  If he's spying, then, geez, talk about 
your temptations.  It's like trusting someone to infiltrate a ring 
of dealers, but not to teach an anti-drug seminar.  If he's NOT 
spying, it's hard to believe that if he's "out there risking his 
life" (Sirius' words), he's not in some sort of contact with hostile 
forces, either fighting them or talking to them.  So, 90% chance, 
Snape is PRACTICING Defence against the Dark Arts.  What is it about 
teaching it to a bunch of teenagers specifically that worried 
Dumbledore? 

So here's My Theory:  the problem isn't with the Dark Arts.  It's 
with the position of Dark Arts teacher, or to be precise, the Jinx.

Now the jinx is a rumour, but then, so was Snape wanting the job.  
There has been a rather... extreme range of bad luck befalling those 
unfortunate guys.  I'm prepared to believe in the jinx-- let's say, 
it's something as simple as, "no one can hold this job for more than 
a year."  

It is my opinion that whatever it is in life that Snape wants, it is 
NOT teaching grade school. I think he's there because Dumbledore 
asked him to at the end of the war-- because he was hard-pressed for 
a head of Slytherin, and because he was worried about what would 
become of Snape.  So let's say he goes to Snape and says, "Well, my 
little ray of sunshine, do an old man (to whom, ahem, you owe your 
life and liberty) a favour and come back to Hogwarts."

Let's say Snape is not willing to refuse Dumbledore anything he 
might ask, but, wow, that doesn't really sound like his idea of 
fun.  So, Slytherin that he is, he sneakily places the jinx on the 
job he immediately assumed he'll be offered:  Defence against Dark 
Arts, what he was famous for at school.  That way, he'll HAVE to 
leave, and if he leaves messy, well, who cares?

But Dumbledore, super-sneaky guy that HE is, fakes him out and puts 
him in Potions instead.  So now Snape is stuck-- bound by his duty 
to Dumbledore.  Every year, he asks for the DADA job as a way of 
saying, "NOW can I leave?". The second he gets the job it's only a 
year till he can be out of there like a bat out of hell, if I may 
borrow the expression from Slick over at Sugarquill (who for some 
reason won't acknowledge co-authorship of this majestic theory ;) ).

So what did Rowling mean by "bringing out the worst in Snape"?  That 
depends on what you think 'the worst' in Snape is.  For the above 
reasons, I think the 'alcoholic' analogy just doesn't wash.  And if 
Dumbledore worried about Snape's cruelty, you'd think he'd have done 
something about his standard-issue teaching methods.

No, I think we have not yet found out what the worst in Snape really 
is.  I'm a root-causes sort of person, and I believe the root of 
Snape's cruelty is his self-destructiveness.  I think he's someone 
prone to despair, and Dumbledore is quite right to worry about what 
would become of him if he left Hogwarts.  To be blunt, I think 
Dumbledore is worried that if released of his duty to Hogwarts, 
Snape would walk up to Lucius Malfoy at the next Death Eater 
jamboree and say, "Guess what, genius-- turns out I really WAS 
spying for Dumbledore.  You guys want a piece of me?"

Well, that's my theory.  Okay, it's more of a plank with a 
hankerchief nailed up to it, but it awaits you canon fire...

Sydney