Cities in Flight Themes
To a very great extent, Blish's social concerns are his great theme in Cities in Flight. America, he suggests, is at a crossroads. Western civilization is wearing out in a very real sense and is about to be replaced by something new, what Blish rather clumsily labels Earthmanist Culture. Through the four books of the tetralogy readers see this culture grow, pass through the various stages predicted by Spengler and then itself begin to decay. Blish ends the series with the ultimate in cultural collapses as Mayor Amalfi, protagonist of much of the series, intentionally sets off an explosion which will destroy, and then recreate, the entire galaxy.
Another theme of some importance here is the necessity of faith and, more specifically, a faith based upon rational analysis. Blish's main characters are not conventionally religious people, but they are believers of a sort and they have an abiding, almost mystical faith in things outside themselves. They are sometimes loners, but they invariably care about humanity as a whole. They have a sense that the absolute does exist and that it exists within the realm of free rational inquiry into the universe. Blish's heroes, in short, are technocrats in the most positive sense of that term. Science, properly handled by men of good will, can save humanity. Those who reject scientific knowledge in Cities in Flight invariably do so out of irrational fear. The relationship between faith, reason, science, and morality continued to obsess Blish throughout his career and, as he grew older, he became less sanguine about the value of both reason and technology. This, in fact, became a central theme of A Case of Conscience (1958).