Men can know the nature of things - Henry Kuttner

If a scientifically trained observer sees a gun go off for the first time, he should be able—theoretically, anyway—to work out a formula for gunpowder.

Well, all this belongs to the future. And so do I. Even before the cosmic cleavage altered all history I was a misfit in this civilization. And now it just isn't my world anymore. I don't belong here. So I think I'll take my chances in that other place, where I won't have to get used to the little things that keep bothering me here and bother nobody but me...

This isn't my world, now. Not any more. Not the world I left. This is a world in which no nekronic flash leaped from a box that Ira De Kalb opened and dropped to his hearthstone to infect the world, De Kalb and me. All that did happen once, in another world that hasn't existed since the four of us, a doubled weapon wielded by the Face of Ea, wrought the cleaving apart of two universes. Imponderable forces shifted when that cleavage took place. You and I know nothing about it, for it happened far beyond the perceptions of any sentient creature. But it happened. Oh yes, it happened.