Lessing said that ideas for "The Marriages Between Zones Three, Four and Five" had been with her for about ten years, but she "couldn't think of a way to do it". It was only when she was halfway through "Shikasta" that she realised that she had "created a marvelous format" that she could use for other books, and it was this format, "Canopus in Argos", that made "The Marriages" possible. "Shikasta" was originally intended to be a single self-contained book, but Lessing's fictional universe developed, and she ended up writing a series of five.