Jacob and Locke were talking about that first scene on the beach. My theory: 'Locke' is not Locke, but rather that first guy from the beach taking Locke's form. Which also makes me think that Jack's father and ghost Claire were not Jacob, but this other guy taking their forms. For some reason he can't become corporeal enough to kill Jacob himself, but he can do so enough to pretend to be someone else, provided the someone else is dead.
Yeah, that's what I'm thinking.

How does Sawyer's 'uncle' manage to be part of the Dharma sub crew?
What are you referring to here? The guy from the funeral that took his letter was on the sub?