By His Bootstraps

"By His Bootstraps" is a science fiction novella by American writer Robert A. Heinlein. It plays with some of the inherent paradoxes that would be caused by time travel.

The story was published in the October 1941 issue of Astounding Science Fiction under the pen name Anson MacDonald; the same issue has "Common Sense" under Heinlein's name. "By His Bootstraps" was reprinted in Heinlein's 1959 collection The Menace From Earth, and in several subsequent anthologies.