Snape's Dementor lesson was: a dumb question

[Carol]

No: HPFGUIDX 182578

Carol earlier:
> > The only place in which it's explicitly stated that Lily's
Patronus is a doe is Harry's remark to Voldemort during his Snape
vindication speech near the end of the Battle of Hogwarts, "Snape's
Patronus was a doe, the same as my mother's, because he loved her for
nearly all of his life, from the time when they were children" (DH Am.
ed. 740). <snip>
> 
> Kemper now:
> I agree with Carol's post.

Carol responds:

Thanks :-)

Kemper:
> I wonder:
> Did Snape not want to perform a patronus in front of his class
(especially Harry)? or
> Did Snape truly have a better way of dealing with Dementors?

Carol responds:

It could be both. Now, certainly, Snape's Patronus would be effective
against Dementors. It's beautiful and powerful and he can sustain it.
*JKR* doesn't want to reveal it too early so she doesn't have him cast
it, but we can only guess about Snape's motivations. His job is to
teach the students DADA, and I think he is really trying to do so, but
he might have other reasons for not teaching the Patronus charm to his
NEWT DADA students. After all, it's a difficult spell which Harry only
mastered under special conditions (private instruction from Lupin and
the good luck of having a Dementor Boggart), and he may know (or
guess) that Harry has already taught it to his DA students. However,
as Harry points out to the DA members in OoP, it's one thing to cast a
Patronus in a room full of fellow students and quite another to cast
one when you're facing an actual Dementor. (The whole concept of the
spell--thinking of a happy memory when the Dementor is sucking the
happiness out of you--would indeed make it almost impossible for many
students to cast.)

Since Snape is unaffected by the Dementor that escorts Fudge to
Fake!Moody's office (where it immediately sucks Barty Jr.'s soul) and
Fudge, too, is unaffected--he can actually give the Dementors
instructions and have them obey him--there must really be a better
defense against Dementors, one that Harry has not mastered and would
vehemently reject--Occlumency.

Kemper: 
> During the Battle of Hogwart's we only see Patroni being cast
against Dementors.  Unfortunately, this could be because those
performing the Patroni who were also Snape's DADA students (Seamus,
Ernie, for sure and Luna most likely) no longer trusted Snape's
instruction having killed Dumbledore.

Carol:
True, they would trust Harry and not Snape, but Luna is a year younger
and would not have been in NEWT DADA with Snape, so the Patronus is
the only defense she would know. And if the defense that snapt
recommended was Occlumency, none of them would know that, either.

Kemper: 
> I don't have my book in front of me (someone's borrowing it), but
does Hermione use a Patronus in the Battle?  If so, that may suggest
that Snape's lesson was not as effective as the Patronus.  I see
Hermione's character utilizing a skill/spell if she finds it effective
regardless of whom taught it to her. 
> 
> Kemper, who would've enjoyed reading about that lesson
>
Carol responds:
If the defense Snape recommended as the best defense was Occlumency, I
doubt that he used the lesson to teach it. He was probably aiming his
remarks at Harry, whom he still wanted to "shut his mouth and close
his mind" (quoting from memory here).

As for Hermione's casting a Patronus in the Battle of Hogwarts, both
she and Ron try and fail:

"[Harry] saw Ron's silver terrier burst into the air, flicker feebly,
and expire; he saw hermione's otter twist in midair and fade; and his
own wand trembled in his hand, and he almost welcomed the oncoming
oblivion, the promise of nothing, of no feeling" (649).

But Harry is feeling despair at this point, feeling responsible for
Fred's death and fearing that Hagrid is dead, too, and Hermione's
Patronus is weaker than Harry's, as we see in "The Muggle-born
Registration Commission," and she has trouble sustaining it. It
disappears with a pop when Ron informs them that the Ministry have
discovered the hole in Umbridge's office door and know that intruders
in the building (DH am. ed 264). Ernie, Luna, and Seamus (who only
attended on DA lesson but managed to discover that his Patronus was
"something hairy, Harry") must have been filled with excitement and
adrenaline, and since they were all acting together and they don't
share Harry's (or Ron's or Hermione's) despair, they have no
difficulty conjuring theirs (self-doubt might have been Hermione's
enemy in the MoM and again in this battle--who knows?). Harry manages
to cast his Patronus at this point with "the greatest effort it had
ever cost him" after Luna encourages him to think of something happy
("'We're all still here,' she whispered, 'we're still fighting. Come
on, now. . . ,'" 649). Maybe Luna is naturally resistant to despair.

Anyway, it seems that Snape is right--Patronuses don't always work,
and the despair generated by the Dementors make a spell based on happy
memories very difficult to cast against them most of the time. (Later,
Harry is protected from despair by the Resurrection Stone, or rather
by the company of his beloved dead. I think he would have given up and
yielded to the Dementors if he hadn't remembered the Snitch, 698.)

So, whatever the defense that Snape recommends against Dementors i, it
must be a protection against despair that works for him. And, given
that he can defend himself against LV's invasive Legilimency using
Occlumency and that the Dementors also invade the mind, causing their
victims to relive their worst memories and yield to despair, I think
that Occlumency is what he uses himself and recommends, specifically,
to Harry. But, yes. He probably doesn't want Harry to see his
Patronus, either. A shame. It might have been all the proof that HRH
needed that Snape was on their side.

Carol, thinking that Seamus's "hairy" Patronus must be the boar and
Ernie's the fox, and wondering why either of them would have those
particular Patroni