I haven't thought that much about Rousseau's message (since I don't speak French) but I did fnd it interesting that the Black Rock (ship) provided the ability for the Losties to get into the hatch and now Jack identifies the location of Zeke's "line" by a black rock that he remembers. I'm beginning to wonder if "black rock" is a metaphor for something more significant.

__________________
Things fall apart, the center cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;

--Lines 2-6, "The Second Coming" by Wm. Butler Yeats