The problem with time travel—apart from whether it’s possible at all—is that, if one goes into the past, actions there will alter the timeline so that, when one returns to one’s own time, things will have changed. “All You Zombies—” is essentially a thought problem that asks, “Would it be possible, through time travel, to become one’s own parent?”

The story manages to prove that such a scenario might, indeed, be possible. It’s only doable, however, if the protagonist travels back in time to arrange things to make them possible. The narrator, a time traveler for the futuristic Temporal Bureau, travels from 1993 to 1970, where he meets himself from that year and takes himself back to 1963. In 1963, he impregnates his earlier, female self, then time-travels to 1964, where he kidnaps his female self’s baby and takes it to a 1945 orphanage, where it will grow up to become his own female self who gets impregnated by his later, male self, and, even later, become the time agent who engineers the entire sequence of events.

The implication is that, somehow, the time agent created himself through his time-traveling actions.