Ghosts and Inferi ("Ghosts are transparent")

[pippin_999]

No: HPFGUIDX 167453

Career Advisor:
> > In HBP Snape asks Harry to explain the difference between Ghosts and
> Inferi. And Harry's infamous answer is that: "Ghosts are transparent."
> >
> >   But why does JKR have Snape ask this seemingly bizarre question?
> >
> 
> JW:
> 
> On the most basic level, it is background info and foreshadowing for
> the later confrontation with the inferi in the cave.  Anybody see
> anything deeper than that?
>

Pippin:
It echoes Snape's question in PoA about how to tell the werewolf
from the true wolf. Presumably the reason it's important to be able
to tell the difference quickly is that one is far more dangerous to
wizards than the other. Ghosts in the Potterverse are generally
friendly and mostly harmless, as far as we've seen. If you allowed
the Inferius of a newly dead acquaintance to approach you, 
mistaking  (or hoping) that it was a ghost, it would probably 
be the last mistake you ever made.

Pippin