S6E17 QUOTATION

"At the innermost core of all loneliness is a deep and powerful yearning for union with one's lost self." --- Brendan Francis

As I have stated previously, the characters in LOST all were deeply lonely individuals.

Jack is an example of the disjointed loneliness. As his consciousness dies in the bamboo thicket, his subconscious is entering the back door of the church, to be joined back into one self (soul).