Most science fiction—or sci-fi or speculative fiction—deals with the following issue: What would happen to people and society if advanced technology was available? What, for example, would happen if people could transport themselves instantly from one place to another? What if society could predict future crimes? What if humankind was immortal? What if humankind could travel back and forth through time?

That last question is the one posed in the sci-fi short story “All You Zombies—” by Robert Heinlein. The main character is a time traveler who goes back to his own past and manipulates events so that he gives birth to himself and thereby preserves his own existence.

The story explores the implications of time paradoxes. The most famous such conundrum involves someone who travels back in time, meets his parents before he was born, and kills them. Does this mean he ceases to exist? If so, then he never goes back in time to kill his own parents, and they give birth to him, and he grows up to go back in time and kill his parents, and the cycle repeats over and over.

In “All You Zombies—,” the narrator does the opposite: He takes actions involving his own past that help to ensure that he survives.