“Everything Happens for a Reason”

In essence: All the survivors were fated, as John Locke has said, to be on the flight, and to end up on the island. In other words, the island chose them.

Support for this theory: The pre-island connections between castaways keep adding up. And incidents like Claire’s psychic convincing her to take the fatal flight (and playing a part in Eko getting on), Hurley making the flight despite all odds, Jack talking his way (or, his dad's body's way) on board and Sawyer getting deported lend a lot of credence. Every character we see seems to have had a reason for being on that flight of all flights.

Poking holes: The producers have said there’s a rational, scientific explanation for everything that’s happened so far, a statement that’s been held up to a lot of skepticism with each passing episode as the faith and mysticism have been piled on. Evangeline Lilly thinks, "Lost is a very big metaphor for every single character's mental state of being, psychological, and emotional state of being and we're on this island to be mentally, psychologically, and emotionally found. We were all chosen specifically because we will facilitate that for one another."