All You Zombies

It was written in one day, July 11, 1958, and first published in the March 1959 issue of The Magazine of Fantasy & Science Fiction after being rejected by Playboy.

"'—All You Zombies—'" chronicles a young man (later revealed to be intersex) taken back in time and tricked into impregnating his younger, female self (before he was forced to undergo sexual reassignment surgery); he turns out to be the offspring of that union, with the paradoxical result that he is his own mother and father.

Cajoled by the Bartender, the Unmarried Mother explains why he understands the female viewpoint so well: he was born a girl, in 1945, and raised in an orphanage.

Complications during delivery, by Caesarean section, rendered the female organs unviable and the physicians gave her a gender reassignment.

The Bartender then drops the Unmarried Mother in 1985 at an outpost of the Temporal Bureau, a time-traveling secret police force that manipulates events in history, to protect the human race.

As he beds down for a much-deserved rest, he contemplates the scar left over from the Caesarean section performed when he gave birth to his daughter, father, mother, and entire history.

Philosopher David Lewis considered "'—All You Zombies—'" and "By His Bootstraps" to be examples of "perfectly consistent" time travel stories.

[4] Stanisław Lem, in his monograph Science Fiction and Futurology, mentioned "'—All You Zombies—'" as an example of a minimal possible bootstrap paradox in SF.