Imagine that someone in our future is equipped with a device capable of delivering packages to the past. He makes a list of thirty or forty of the most influential people in the U.S. as of (say) the 1850's, prepares for each a package of history books, and delivers the package to the recipient's desk a week or two before some prominent natural event, such as an earthquake or eruption, is due to occur.
Each package includes a dozen identical color photographs and a cover letter. The letter predicts in detail the event about to occur and explains that the package is being sent in the hope of preventing a very bloody war. The photographs could not have been produced with mid-19th century technology; the hope is that they plus the prediction will be enough to persuade at least some of the recipients that the package really is from the future. What happens?
Bill's guess was that the deep South states would respond by immediately seceding. My reaction—not inconsistent with his—was that what the intervention has created is a high stakes game of Chicken. Leaders in the North can tell those in the South that they might as well surrender now, since the alternative is a long and bloody war that they will lose. Leaders in the South can argue in response that the North, knowing what the cost of the war will be, will have to back down and let them go.
It could make the plot of an interesting novel. If I were writing it—not likely to happen—I would be inclined to show the intervenors from the future as naive do-gooders who take it for granted that if only both sides had known, the war would of course be averted. The recipients are both more realistic and more sophisticated; each sees both his new information and his knowledge that others have the same information as merely additional elements in the complex political game already ongoing.
One question is how long before the war the intervention happens. Another is whether the recipients attempt to make their new knowledge public, and if so how many people believe them. Readers are invited to indulge their own imagination.