Jack and John by Suther23

Maybe the characters Jack and Locke are both very tragic. We know that Locke was a sad man, shouting at the world for being told what he couldn't do. One of the reasons he became a man of faith was because life was so unfair to him.

After he got on to the island, he was fully a man of faith. This was his strong weakness. His 'gullibility'. His inability to have reason. Therefore, the smoke monster used him.

Jack, on the other hand, is a man of science. He thinks more logically. Maybe this is (was?) also a weakness. He denies everything that involves miracles. Therefore he struggles with the island's mysterious happenings.

Jack and Locke have to make decisions together. Yes, they fight a lot when doing so. However, in season 4 the people divided into two groups, Jack and Locke being the leaders. A lot of people died in Locke's camp, which portays John's guillibility. Jack got of the island and the rest of the people died, which portays the fact that he's precipitous.

Jack and John both have been leaning to the other side. Locke was more of a man of science in the second season, whereas Jack has been more of a man of faith the last seasons. Locke became a man of faith again when his faith in the island was restored.
I noticed that Jack is irritated with the entire concept of faith. He was partly broken because the things that John had been telling him finally got to him.
But Jack, also, fails to change.

Jack and John have to make decisions together. In this unigue relationship, they keep eachother, their beliefs, in balance.