The hanging man?

Rating: 10/10 (13 April 2008)

Towards the end of the movie, Chuck tells his friend how he had contemplated suicide, going so far as to rehearse it. Now, Chuck is marooned on an island where the struggle to survive takes up most, if not all, of his energy, yet in order to test the hanging tree, he goes to the trouble of searching out a tree from which he can make a fairly realistic human-like figure. All he needed was a lump of wood of approximately his own weight. So, why did he do it? Consider that Wilson could represent an externalization of Chuck's conscience or Ego, so the tree-body would then represent an externalization of some aspect of his body, his Id or sexuality. And notice that Wilson is lost at sea, while the tree-man is left at the highest point of the island. It's as though Chuck takes his body back before he leaves the island, and takes his "head" back just before he is rescued and returns to the human world.
So, the question: if Chuck externalized his "head" and his "body", what part did he keep to himself, so that he remained alive? His Soul?