Was Windom Earl trapped in the black lodge while deployed to Twin Peaks for project bluebook? Was the Windom Earl we saw on Twin Peaks a doppleganger? I believe so - he escaped from a mental institution and went back to twin peaks because his 25 years were almost up. It's understandable that he forgot exactly where the entrance is after all that time. The main clue to this is when Leland/BOB is being interrogated by Cooper after his arrest. He is asked 'did you kill Teresa Banks?' He replied, as BOB - 'I guess i sorta did - I have this thing for knives' - Then he turns to Cooper and says  'Just like that time in Pittsberg'. How would BOB know about that - Unless he was possessing Windom when Windom stabbed Cooper in Pittsberg. It would certainly explain why Windom Earl became a homical maniac and killed his wife. Can anyone explain how BOB knew about Earl stabbing Cooper in Pittsberg?

I don't believe Earle has ever been trapped in the Black Lodge.BOB knows about this incident not because he actually performed the stabbing,but because in a sense he was there(at least in the black lodge version of events,we know there everything is backwards and turned upside down,future and past are mixed)

You can't just attribute ALL evil in the Twin Peaks world to Bob.

I believe Earle and only Earle was responsible of what happened in Pittsburgh, no BOB involved at all... And BOB knows because he's an entity from another world, a spirit... He just *knows*, sees inside Coop, is omniscient, whatever... Just like the Giant knew about Leo locked inside a particular prison in a specific date...

Also, everything dealing with a person's mental being can be looked at from two points of view - like most of Lynch's movies there's a duality involved. Cooper's mental change at the end can also be explained without bringing supernatural spirits into the world. Same goes for Leland's "possession". I think it's important to keep that in mind. The supernatural aspect is not needed for the story to work.

Yikes.  I think a more accurate way to say that is that TP is certainly a supernatural narrative, but that people wishing to deny such elements can, with some effort, piece together a "rational" narrative that is nowhere near as meaningful.

Maybe you can say that the Laura/Leland abuse can be explained as you suggest... but not much else.  How would you rationalize the visions various people have throughout the series?  How are so many people seeing visions of the same figment/manifestation of Laura's abuse (i.e., BOB)?

I agree that it's a little crazy to try and attribute everything to supernatural influence... but I also don't condone the opposite, which seems to be the suggestion above.

Let me put it this way. What we see is an abstraction - distorted. We shouldn't really be seeing those dream sequences - we are observing from outside the TP world. From someone like Dr. Hayward's perspective there is nothing supernatural occuring. I guess what matters most is how do things look like to the characters within the story. So, which characters believe they've experienced the supernatural?

1. Cooper
2. Briggs (unless this is considered to be extra-terrestrial in nature - not really supernatural)

...others... 

"I have this thing (Leland) for knives. Just like that thing that happened to you in Pittsburg that time, huh Cooper?" 

I think this words are very important because, why Bob said "I have this thing (Leland) for knives. Just like that thing that happened to you in Pittsburg" if this doesn't mean use a body like a symbolic weapon to kill? and I guess Bob tried to say that a body was used like a "knive" in that time too. 

Sorry for my bad English, I don't speak English very well.