A pre-mortem makes it possible to voice doubts when a group is nearing a decision, a point at which dissent is otherwise hard to raise.

it's beautiful because when people are coming close to a decision it becomes difficult to raise doubts or to raise questions people who are flowing the group down when the group's is nearing a decision a perceivers really you know person I mean you know this you want to get rid of them and the pre-mortem legitimizes that sort of descent and that sort of doubts not only legitimizes that too much rewards it