LAST EDITED ON 06-01-10 AT 09:33 PM (EST)>But the Island wasn't Purgatory. Only
>the Flash-Sideways in Season 6.
>Whether they planned it that
>way is debatable, but I
>can't criticize them for denying
>Purgatory was the point.
The criticism is that they denied the island was purgatory back in Season One, at which time it most likely was a story about some version of limbo in which LOST souls find themselves.
Because people guessed it, and the writers then had to deny it to keep the thing a mystery, they then morphed into a version where the island was real, which presented certain problems in that they had incorporated a supernatural monster from Day One, which didn't needed to be explained if the castaways were dead, but did need to have a rationale if they were in the South Pacific.
Most people who have followed what was said about the monster early on thought it was Cerberus, guardian of the gates of Hell.
The writers have said that Jacob wasn't even discussed until Season 3, and any viewer knows that the monster was never seen changing from smoke to human or vice versa until Season Six ... Terry O Quinn had no idea he was playing the smoke monster when he played the "resurrected" Locke in Season Five.
The Flash Sideways was revealed to be a limbo state, not an alternate time line. That's why Jin and Sun suddenly started speaking English and telling Sawyer they were perfectly fine. It was a limbo where they were unconscious of being in limbo and thought it was real until they saw flashes and were awakened. After Locke awakened, he knew the truth and told Jack that he had no son.
After they awakened to the truth, they proceeded to the church, where Jack, the last to awaken, saw his flashes after touching the coffin. Note that when Kate arrived with him at the church, she knew and he did not. The church was the departure lounge for the white light express within the limbo world.
Ben stayed outside, because he was remaining in limbo to enjoy some time with Danielle and Alex. Eloise reprimanded Desmond (twice) because she wanted to hang on to an existence where she had not shot her son.
As far as I can tell, the whole sunken island shot was mostly there to make people think that Jughead had done something to create a split reality. It was part of the long con for the season ...
As for what Christian said, he said it was all real, but he also said the church with no time was real, so that really says nothing about the island or the Flash Sideways. However, no one on the show is saying the island events weren't real; they are real as of the end of the show. How it began is another story.
The reason I'm using the word Limbo is that Limbo, which is from Latin for "border" and shares the root of "liminal" was conceptualized as the border to Hell, which would work rather well with the island as cork. Limbo is the place for people whose souls are not bound to either Heaven or Hell, perhaps because they died prior to Christ. Unbaptized infants went to Limbo. (Remember Aaron's baptism?)
Purgatory is the place where souls who did not commit mortal sins can expiate their sins and then move on to heaven. Murder is a mortal sin, so several Lostaways were never eligible for Purgatory under the strict meaning.
Probably it was not exactly Limbo, but it's a better term than Purgatory, so strictly speaking the writers could say the island was not Purgatory. However, after the Third Policeman hint in 2.3, the writers went on record that the Losties were not DEAD ... which is the twist of TP. I personally think that was a turning point where the island story turned more towards some sort of real world place.
Then they took the "dead" idea and tacked it onto the end.