"Well, you need a man who'd know the historical background, and you'd need a man with a powerful creative imagination, who is used to using it inside rigorously defined limits. Don't try to get them both in one; a collaboration would really be better. Then you work from the known situation in Europe and in America in 1492, and decide on the immediate effects. And from that, you have to carry it along, step by step, down to the present. It would be a lot of hard and very exacting work, but the result would be worth it." He took a sip from his glass and added: "Remember, you don't have to prove that the world today would be the way you set it up. All you have to do is make sure that nobody else would be able to prove that it wouldn't." "Well, how could you present that?" "As a play, with fictional characters and a plot; time, the present, under the changed conditions. The plot--the reason the coward conquers his fear and becomes a hero, the obstacle to the boy marrying the girl, the reason the innocent man is being persecuted--will have to grow out of this imaginary world you've constructed, and be impossible in our real world. As long as you stick to that, you're all right." "Sure. I get that." The plump man was excited again; he was about half sold on the idea. "But how will we get the audience to accept it? We're asking them to start with an assumption they know isn't true." "Maybe it is, in another time-dimension," the colonel suggested. "You can't prove it isn't. For that matter, you can't prove there aren't other time-dimensions." "Hah, that's it!" the sandy-haired man exclaimed. "World of alternate probability. That takes care of that." He drank about a third of his highball and sat gazing into the rest of it, in an almost yogic trance. The plump man looked at the colonel in bafflement. "Maybe this alternate-probability time-dimension stuff means something to you," he said. "Be damned if it does to me." "Well, as far as we know, we live in a four-dimensional universe," the colonel started. The elderly man across from him groaned. "Fourth dimension! Good God, are we going to talk about that?" "It isn't anything to be scared of. You carry an instrument for measuring in the fourth dimension all the time. A watch." "You mean it's just time? But that isn't--"