The world of science fiction was fairly small in the 1940s and 1950s.

Most of the writers knew each other and read each other's work. The fiction of Robert A. Heinlein and Isaac Asimov was particularly influential on other authors and James Blish was no exception. Any discussion of Cities in Flight might be profitably carried on within a context provided by having read such novels as Heinlein's Double Star, Methuselah's Children, and The Moon is a Harsh Mistress, as well as Asimov's original Foundation trilogy.

Central to these works is a belief in the inherent superiority of rational thought to faith and of science to religion. Although Heinlein and Asimov are both advocates of democracy, neither puts much faith in the abilities of the common man. Both depict politics as being a matter of the few manipulating the many, sometimes for personal gain, sometimes out...