Known unknowns

Only another 266 days of hollow meaningless existence before Lost returns with season 4. In the meantime, there seem to be a few good books worth a read: Finding Lost: The Unofficial Guide and, in particular Living Lost: Why We're All Stuck on the Island by The Always Interesting J. Wood. (Yes, that is his full name.)

Not unlike in the show itself, we're hearing plenty of mysterious whispering from fans, producers and crackpot theorists; none of which gives much away but are interesting nevertheless. To take the Rumsfeldian view,

"...we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns — the ones we don't know we don't know."

So how about some of those known unknowns that we're hoping will become known knowns by the end of next season? From reliable sources, like interviews and podcasts with the producers, it seems likely that (not before time) we'll discover much more about: tetchy spectre Jacob, who's been compared in significance with the wrinkly Emperor from Star Wars; Michael and Walt, although who really cares about the former; Libby, the mentalist boat-lender; Danielle Rousseau, deranged pyromaniac for hire; Penny, who we're told is an important character in the overarching story; and finally, four-toed colossus, who might help unravel some history and mythology behind the The Island.

Which mystery would you most like to see explained in season 4?