In the season finale of Lost, the question persistently asked by the narrarator and depicted by the button-pushing activities of characters like Locke and Echo, a spiritualist and a priest, is “Can we survive on faith alone?” Faith is pitted against the reason of science ala Jack, whose calculating rationale refuses to believe that pushing the button has anything to do with survival on the island. A take-charge-kind-of-guy, Jack leads the marooned plane-crash survivors through knowledge, medical and rational. He repeatedly saves lives through his knowledge, patching up gun wounds and fractured legs. Apparently, they cannot survive on faith alone.
However, as the season finale depicted, button-pushing was integral to island survival-if you are in the bunker. Come to find out, the button defuses a magnetic charge that continually builds up, a charge that draws everything magnetic towards it, the charge that caused the plane crash to begin with. Pushing the button prevents further crashes and bunker explosion. It also provides purpose. It gives Locke and Echo something to do, to find significance in, in an otherwise meaningless existence. Faith is life-preserving-literally and psychologically/spiritually.
Conclusion: Both faith and reason are necessary for survival on the island. Trust within the group, faith in the possiblity of escape, hope for interpersonal reconciliation are necessary in order to avoid despair. Of course, reason will be necessary to figure out where we are to place our hope. Is it in the “others”? An magnetic detection team? The gods of Echo, Sayid or Jack himself? Reasoned faith in what will enable them to survive?