No canon for why Snape knows about Horcrux

[Kemper]

No: HPFGUIDX 148220

Catherine:
  I think you make some excellent points, but I have o disagree on one
thing. I don't think Dumbledore told anyone else about the Horcruxes
except Harry. I don't even think he's told MgGonagall about them, and I
don't think he'd tell Snape either. Especially if Snape is DDM, spying
on old Voldie, I think it would be extrememly dangerous for him to have
told Snape. No matter how good an Occlumens he is, Voldie is a powerful
Legilimens. No matter how much he trusted Snape, I don't think he would
have taken that chance with such important information.
   ..
.
Kemper now:
I agree that DD may not have told Snape anything about what he was doing.
However, I believe we are given evidence enough about Snape's intelligence
for him to put that together without talking with Dumbledore.  I am of
course assuming Snape knows what a Horcrux is, given that knowledge, I find
it hard for Snape to be at a loss for Voldemort's survival.  Snape is a
brooder, or that's my impression based off what is gleaned from Snape
during Occulemency lessons and his worst memory, so it would seem like he
would have given Voldemort's rebirth some thought.

Kemper


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