Reason Dumbledore trusted Snape.

[eggplant107]

No: HPFGUIDX 171659

Jessica Wrote on July 12

> I have even entered the thought that she
> may have become pregnant to Tom Riddle.
> So, Snape could be his son. In my theory 
> she was too afraid to tell Tom that she 
> was pregnant so she marries a muggle out 
> of desperation who isn't nice to her. So,
> Dumbledore finds out about it later and
> reveals this to Snape. When Snape finds
> out whatever circumstances this happened
> under, he hates Voldemort and turns to 
> the good side. This could be Dumbldore's
> powerful motive for believing Snape. 
> Also explains Snape's very powerful 
> magical ability.

That is an interesting theory. If could also explain Snape's fondness
for his nickname, "Prince" because he wanted to emphasize his mother's
side of the family, and "Half Blood" because he's rather be known as
the son of a Muggle than the son of Voldemort.

However I'm not convinced Snape turned to the good side, a slight tilt
in that direction over the years maybe. In my theory Dumbledore trusts
Snape because years ago Snape made an Unbreakable Vow to protect the
life of Harry Potter. Dumbledore did not know that Snape made this
noble sounding vow for less than noble reasons.

Suppose Snape heard every word of the entire prophesy but Dumbledore
sincerely believed he only heard half; we know for a fact he only told
Voldemort half but I think the reason is that Snape knew attacking the
baby Harry would be very dangerous and he wanted Voldemort dead.
Suppose Snape wants to rule the world but 2 wizards stand in his way,
Dumbledore and Voldemort. One down one to go, and that's why he needs
Harry alive until he can finish off the Dark Lord.  

Eggplant