I suspect time travel is responsible for most of the paranormal/supernatural phenomena that have occurred – Alpert’s apparent non-aging, the whispers, Walt appearing in places he shouldn’t be, appearances by the dead, moving the Island, etc. The “synchronicities” that occur regularly could be explained by time travels deliberately manipulating certain events.
Lost: Overview of My Current Theories
See also: LOST Theory: The Island is the Village from the Prisoner (which contains some Prisoner spoilers).
And: Lost Theories