I’m sure the title of this episode refers to Ben’s occupation in the flash-sideways. The word doctor comes from the latin doctoris which means teacher. However, these titles usually have a double meaning, so maybe the Ben on the island has to do some first aid on someone else.
Micheal Emerson was recently on Jimmy Kimmel live: (This video has mild spoilers, if you want to stay completely spoiler free don’t watch it or read the paragraph below it.)
So, if you didn’t watch it, Micheal said that Ben is still alive in the fourth episode. The promo for this episode makes it seem like Ben is going to die, but according to Micheal Emerson, he was shooting for the fourth to last episode at the time of this interview. So it seems obvious that he won’t die, but it think it would be pretty interesting if Ben died in only one of the two realities. Emerson also said that his role as a teacher in the alternate universe will be important and not just something the writers did for fun which I hope is really true. I hope that the whole parallel universe thing can be resolved in a way that amazes me and I hope it happens before the finale.