I am confused by people's confidence that the stuff on the island actually happened, in the real (not some spiritual world).
My interpretation is that everything on the island, and on the alternate world, was all a spiritual journey not in the physical world. Otherwise you want me to believe:
1. A bunch of people improbably survived the plane crash
2. They also survived a nuclear explosion that somehow shifted them in time
3. They were able to disengage a magic island from time
4. They took up with an immortal man (Richard)
5. They heard and sometimes interacted with people in purgatory.
6. On an island with a cork in the middle that somehow was the key to everything
More likely is that the island was a purgatory for those that were flawed, but able to be fixed. Richard died when his ship hit the island. The people on Oceanic all died. The people on the helicopter (e.g., Faraday) all died. All that were flawed in a major way appeared to survive on this spiritual island, where they had to work out their sins until they were ready to go on.
What is wrong with this scenario? Two major problems are:
1. Juliet. She was putatively imported to the island to help the others (because babies were dying for reasons they never explained), no reason to think she died or that the island was fake. Unless maybe her ex-husband had her killed, and then she was sucked into the spiritual world of the island, with Ethan and Richard and such. That seems just as reasonable as 1-6 above. But also it isn't clear what spiritual flaw Juliet had, which goes against my thesis.
2. Richard's earlier interactions with Locke, Sawyer, Kate, etc. when they were kids. I admit it is harder to explain this using the same logic as with Juliet. But to say things all happened in the spiritual realm isn't to say it's complete BS. Perhaps the spiritual realm could reach out to these people, like ghosts, and that's how they interacted with Richard. Far fetched? You bet. More far fetched than 1-6 above? Not by my lights.
I'm not trying to be stupid here, but just curious why people are so confident the island timeline is "real". There is LOTS of room for interpretation here, precisely because they did so crappy a job resolving so many issues.