Harry's reaction - One or them

[kiroo4]

No: HPFGUIDX 138560

I've been wondering on this for a while and haven't see a post with 
it.  My questions centre around why did he think this, and how on 
earth would he have expected it to work?  It could be as simple as 
denial, but then why word it that way?  He's already seen the method 
used.

Chapter 28.  UK pg 557

Terror tore at Harry's heart.... he had to get to Dumbledore and he 
had to catch Snape.......  somehow the two things were linked....  he 
could reverse what happened if he had them both together.....  
Dumbledore could not have died.

Tanya