Gulf is a novella by Robert A. Heinlein, originally published as a serial in the November and December 1949 issues of Astounding Science Fiction and later collected in Assignment in Eternity. It concerns a secret society of geniuses who act to protect humanity. The novel Friday, written in 1982, was loosely a sequel.
The story postulates that humans of superior intelligence could, if they banded together and kept themselves genetically separate, create a new species. In the process they would develop into a hidden and benevolent "ruling" class. The story invokes the notions of the General Semantics of Alfred Korzybski and the work of Samuel Renshaw to explain the nature of thought and how people could be trained to think more rapidly and accurately; critics have said that both systems are misrepresented and never claimed the kinds of results shown in the story. The material on human intelligence and self-guided evolution is intermixed with a more standard "secret agent" adventure story.
One of the story's key characters, Hartley M. "Kettle Belly" Baldwin, appears as a much older man in the later novel Friday, there known mostly as "Boss." (Boss briefly mentions Gulf's protagonists Joe and Gail as examples of "honorable hatchet men.") While the earlier version of the character had strongly argued that smarter people are, and ought to be, separate from the human race in general, Boss appears to categorically deny this premise.
The dialogue between the male and female leads, Joe and Gail, is reminiscent of the exchanges between the characters in Heinlein's last five novels from 1980-1987. Gail is strongly evocative of the powerful, free-spirited female characters from these novels. Joe is quite similar to the more taciturn male heroes such as Zebadiah Carter and Richard Ames from, respectively, The Number of the Beast and The Cat Who Walks Through Walls.
The supermen communicate in an arcane language called Speedtalk, which is both unintelligible and unlearnable by outsiders. Speedtalk is founded upon two principles: a reduced lexicon, and an enlarged phonology.
Any English sentence can be composed from a small vocabulary, such as the word set of Basic English. Also, although the human vocal tract can produce hundreds of different sounds, no existing human language normally makes use of more than a few dozen of them. In Speedtalk, each word from the Basic English set is assigned to a different sound. A sentence in Basic English can therefore be pronounced in perhaps one fourth the normal time.
This story was written for the "time travel" issue of Astounding Science Fiction. The issue was prompted by a letter from a reader commenting on the stories in an issue, referring to the stories by author and title, and offering his respective praise and derision for those works. The magazine commonly received these kinds of letters; however, in this case, the reader described an issue whose cover date was more than a year away. Editor John W. Campbell printed the letter, then set about making the predictions come true by arranging with the authors mentioned to write and submit stories with the given titles. Gulf, by Heinlein, was one of the stories involved.
Heinlein has written that he had a different idea for the story originally, but decided that it was too large for a novella and could not be written in the time he had available. The idea later became one of the inspirations for his novel Stranger in a Strange Land. For the magazine, he decided that the gulf between man and superman would provide an adequate basis for the title.