Constant and Variable
I have a theory on the idea of a constant on or off of the island. The two episodes that elude to this math type idea of time are the constant the variable. It seems that there are two possibilities of a constant. Richard Alpert is clearly the constant on the island. Desmond is a constant off the island. Clearly Desmond will return. There is no reason why they would keep him with the show unless he was going to crash on the island in his boat. The Variable is a very interesting episode because while it is centered around desmond, he can’t be the constant and the variable. I believe the variable is Ben, and whether he choses to be selfish or, selfless will determine the fate of everyone. Some people say Juliet is a variable but I don’t see it.
The other theory is that every individual has their own constant and variable which is possible but would not really make sense with the amount of times that the writers have eluded to this type of idea.