for the longest time i thought there was a time loop, and for me, i thought that would've explained everything...
for example, if time was looping on the island, then eventually there would be a john locke on the island and a john locke in the real world, a charlie pace on the island and a charlie pace in the real world, etc... with that in mind, i figured john could walk and rose overcame cancer because they had developed those problems yet back in the real world and those two conflicting states of health couldn't exist at once... keeping conflicting states in mind, i thought that's why michael couldn't kill himself off island-- because he couldn't be both dead in the real world and alive on the island. (i also assumed the smoke monster's role was to eliminate inconsistancy.)
not to mention if time on the island was circling around, then people could step on and off during various time periods... i figured that's why richard alpert appeared not to age.
i also thought that a time loop could explain why 815 was found on the ocean floor... if desmond not pushing the button caused the loop to shift directions, then there would be two planes existing at the same time... one crashing on the island and a second crashing into the ocean. (but it turned out to be an elaborate fake, which strangely enough, seemed less plausible to me than a time loop.)
lastly, if time was looping around, then the island would physically move around since time and space are connected... i assumed that this movement would explain why it couldn't be found and how the black rock ended up in the middle of the island.
anyhow, as the show is coming to an end, i really don't think there's a time loop on the island.
what were some of your theories that are now debunked?