All the Myriad Ways

by Larry Niven

Detective-Lieutenant Gene Trimble suspects that the recent spate of suicides and violent crime is somehow connected to the discovery that the many worlds interpretation of quantum physics is real and each of those worlds can be traveled to.

— Michael Main

There were timelines branching and branching, a mega-universe of universes, millions more every minute. Billions? Trillions? Trimble didn’t understand the theory, though God knows he’d tried. The universe split every time someone made a decision. Split, so that every decision every made could go both ways. Every choice ever made by every man, woman and child on Earth was reversed in the universe next door.

“All the Myriad Ways” by Larry Niven, in Galaxy, October 1968.

The Number of the Beast

by Robert A. Heinlein

Semi-mad scientist Jake Burroughs, his beautiful daughter Deety, her strong love interest Zeb Carter, Hilda Corners (“Aunt Hilda” if you prefer) and their time/dimension-traveling ship Gay Deceiver yak and smooch their way though many time periods in many universes (including that of Lazurus Long), soon realizing the true nature of the world as pantheistic multiperson solipsism.

In Heinlein’s first version of this novel, written in 1977, the middle third of the story takes place on Barsoom, but in the 1980 published version, Barsoom was replaced by a futuristic British Mars

— Michael Main

Sharpie, you have just invented multiperson solipsism. I didn’t think that was mathematically possible.

The Number of the Beast by Robert A. Heinlein (Fawcett Columbine, 1980).

Thomas Schlück

translator