What did Snape know, and When did he know it?

[houyhnhnm102]

No: HPFGUIDX 169365

Carol:

> Not necessarily. If Snape knows that Wormtail is the 
> spy and that Peter Pettigrew is Wormtail, then he knows 
> that Pettigrew is the spy.

> Let me put it as a syllogism.

> Wormtail is the spy.
> Peter Pettigrew is Wormtail.
> Therefore, Peter Pettigrew is the spy.

> So, if Snape recognized the names on the map (and knew 
> which name belonged to which Marauder, Moony being obvious), 
> he must have known who Wormtail was. [...] But *if* he did, 
> and knew who was whom, we have a problem.

houyhnhnm:

Better:

Snape knows Wormtail is the spy.
Snape knows Peter Pettigrew is Wormtail.
Therefore, Snape knows Peter Pettigrew is the spy.

We have no evidence on which to establish the truth of 
the major premise. That is why I don't think your 
argument is sound.  The fact that Snape recognized 
Wormtail as a Marauder, if he did and I'm not convinced 
that he did, has nothing to do with recognizing Wormtail 
as the spy.

We would need some kind of evidence that Snape heard 
of Wormtail the spy while he was spying for Dumbledore, 
from Voldemort or from his followers.

If Sirius' words can be taken at face value, and that's 
a big if, then there were some Death Eaters who knew that 
Peter Pettigrew was LV's spy within the Order.  We have 
no evidence that he was known to them as Wormtail at that time.

I can imagine a scenario in which Snape was nosing 
around the DEs back in the day and managed to find out 
that someone called "Wormtail" was betraying the Order's 
secrets but couldn't manage to find out "Wormtail's" 
real name.  Then the question of whether or not Snape 
recognized Wormtail on the Marauder's Map would matter.  
But that is just wild speculation without any canon support 
whatsoever.

Carol:

> Snape clearly didn't know--could not have known--who 
> the *Secret Keeper* was. Only the Potters, Sirius Black, 
> and Wormtail knew about the Secret Keeper switch, so 
> far as we know.

houyhnhnm:

"Sounds like they think the double-crosser 
double-crossed them.  Voldemort went to the Potters 
on your information . . . and Voldemort met his downfall 
there."  I'm not sure how reliable is any information 
that comes from Sirius, not because I think he is a liar, 
but because he is careless of speech and given to 
hyperbole, but if his words are an accurate representation 
of what the Death Eaters were saying in Azkaban, it sounds 
to me like they did know that Peter was the Secret Keeper, 
and if some Death Eaters knew that, then Snape could have 
known it, too, if he was 100 percent in the loop.

I don't think he was.  I think there is abundant evidence 
in all six books to falsify the ESE and OFH Snape theories.  
Therefore he could not have known, either that Peter was 
the spy or the Secret Keeper.

The fact that Snape knew Peter Pettigrew was Wormtail the 
Marauder (or didn't know) has no relevance to his DDMness 
or lack thereof, in my opinion.