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.

Ch. 25 : Return Voyage - The Time Axis (1949)