Yeah, I think Desmond was the central person for the scientific part of the series and Jack was the central person in the character driven part of the show......
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Desmond must have been present when he moved in time because he changed history when he went back and made Penny his constant....Desmond also had the ability to move within the realities....and in the end had the ability to see how to move on (the ultimate move from one reality to another).....the island seemed to trigger each characters ability at different rates to move within one lifetime, move to different locations, or within different realities, and were triggered by different events....Desmond with the Hatch explosion, Locke with the turning of the wheel, etc.......one could argue they didn't need the island any more in the sideways.....is was like the Ruby slippers in the Wizard of Oz...they had the power all along and just needed to use it.....   See 7 other replies

Alive in Different Realities
Until the final episode I thought one possibility was that they were in both realities at the same time, but the finale killed that theory.Desmond in "The Constant"/The Flash Sideways
For me those were completely different events. Desmond's mind was traveling to different points of his life in the same reality, while in the flash sideways they remembered the life they had before death.Christian Shepard
He did say "this place" but he said it was created to help the characters find each other. Since most of them found each other before entering the church it makes more sense if he was referring to the entire flash sideways. However, depending on the interpretation, I can see where you're coming from.   See 7 other replies

Fair enough. The show doesn't make sense to me if they were all alive and then went to the sideways after they died.....for me, they were all alive at the same moment in the different realities, but existed at different times within the realities....and the seeds of this thinking was with Desmond in "The Constant" when he traveled through time in a given reality....being alive in both, but present in only one....
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I think Christian Shepard said they created "this place" together in the last scene....and I felt he meant the church....implying they created the conditions together to allow them to move on in the church (just a symbol)....not create the sideways....
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Very interesting thought about Ben.....yes, that makes sense....he may have moved on later with Alex, Charles Widmore, Richard, Eloise Hawking, Walt, etc....   See 7 other replies

A quote from Mother pretty accurately sums up many LOST discussions: "Every question I answer will simply lead to another question."Ben didn't need to survive in the 70's to create the flash sideways, in fact some characters wanted Ben to die from the gunshot. Kate decided to save Ben because he was just a kid who had not yet done everything that happened in the future. (Ironically it's insinuated that the Others saving Ben is what caused him to turn into his future self.)The common theory is Ben was waiting to move on with Alex and Danielle Rousseau. Later on Ben may have helped Alex or Danielle remember.I assume Desmond beating Ben caused Ben to remember because the same thing happened while they were alive. A character entered the flash sideways after dying, they weren't in both realities at the same time. It's stated in the show that the dead charters created the flash sideways (Christian Shepard).Why was the island underwater?
1) The writers thought that would be an intriguing way to start the 6th season and make people watch the show.
2) Symbolism - The island is underwater and therefore out of sight. This hints at the dead characters currently not having any memory of the island.   See 7 other replies

Interesting....Sorry, but your comments actually bring up more questions and confusion for me than clarity...but if it helps other people then great!If you are interested....just one of many questions.....why did they need Ben to live from the 70's gunshot to create the sideways and find each other....Ben didn't go into the church and they still moved on.....Ben's touch didn't allow anyone else to remember...in fact, the only reason Ben remembered was that Desmond beat him up (and Desmond was not trying to get Ben to remember).....It's clear to me that they didn't create the sideways, but were in the sideways and their actions in other realities allowed them to remember and create the conditions to allow them to move on.....so, they didn't create the island under the sea.....why would they do that?   See 7 other replies

Series finale spoilers below...Just wanted to clarify - the island was never actually underwater. It was shown underwater in the season 6 flash sideways, which was made by the dead characters to reconnect with each other. From every living characters point of view, the island always remained above water. There was no reality in the show where living characters on Flight 815 landed safely in LA. Because of this, it did matter if Ben lived or died after getting shot in the 70's.   See 7 other replies