(Some Lost spoilers follow.)
“Push the button every 108 seconds or the world will end.”
The only way to disprove that is to not press the button, but—if you’re right—it will be a pyrrhic victory.
Given what the candidates knew, could any of them be truly certain whether Jacob or his nemesis was the villain? Even with the extra information we—the viewers—have... We know that Jacob was not infallible. It seems that Smokey’s goal was originally fully justified, even if his methods weren’t.
This, to me, has been one of the strongest messages of Lost. Logic and science can only get us so far. Often we reach a point at which a decision must be made with incomplete information. We have to make a leap of faith, though one informed by reason.
Reason and faith are not choices, as they are sometimes presented. Nor are they opposed to one another. Rather they are tools we use to live our lives. You have to use both, and you have to use them together.