In the 1967 novel, it’s apparent that Cathedral is occupied by violent, feral children—referred to as “Cubscouts”—who are a deadly menace, likely because they weren’t “machine-reared” like everyone else in industrial nurseries:
Cathedral: a festering sore in the side of Greater Los Angeles, an area of rubble and dust and burned out buildings, a place of shadow and pollution, of stealth and sudden death. Cubscout territory. If <PERSON> cleared the bridge the cubs would take him. The kill would be theirs—and that was bad for the record. <PERSON> was well aware of Cathedral's blood history. Of the runners who never came out. Of the muggings. Of the unchecked violence. Even the police avoided Cathedral. With good reason. They'd sent in a cleanup squad the previous summer to tame the cubs. <PERSON> had known some of the men in that squad: <PERSON> and <PERSON> and <PERSON> 9, all good officers. They'd walked into the jaws of the crocodile and the jaws had closed. None of the squad survived.
Why was Cathedral “an area of rubble and dust and burned out buildings” in the first place? Possibly because it was devastated during the “Little War,” the rebellion by people younger than 21 and less—note that in the movie, the age limit was raised to 30 and less—that overthrew the established order and mandated euthanasia at age 21. Possibly because civilization is beginning to collapse because there is no longer anyone old enough to knows how to build or maintain anything, as <PERSON> concludes when he finally reaches Sanctuary:
There was so much to say to <PERSON>. That the world was coming apart, that it was dying, this system, this culture. 514
That the Thinker was no longer able to hold it together. A new world would be formed. Living is better than dying, <PERSON>. Dying young is a waste and a shame and a perversion. The young don’t build. They use. The wonders of Man were achieved by the mature, the wise, who lived in this world before we did.
Narratively, this suggests that novel authors <PERSON> and <PERSON> chose "Cathedral" as the name of the infested region to symbolize how the youth-obsessed culture of Logan's world had abandoned the belief systems of the past, including religious values for life and a belief in an afterlife, and the self-reflection that comes with a level of maturity people no longer reach.
<PERSON> elaborates on this point in a 2000 interview with <PERSON>:
"I wrote Logan's Run during the Watts riots, when youth were rioting. The book was an implicit criticism of a lifestyle that destroys you and society, a lifestyle where maturity is rejected. You can't live a hedonistic lifestyle and survive--you either die young or it catches up with you... "I think the original movie missed the book's subtext, which is the breakdown of society when youth rules."
Cathedral is occupied by children no older than 13, which becomes apparent when Logan is surrounded by a gang and confronts its leader, whose palm crystal is blue:
“No cubs at fourteen, <PERSON>. Ever heard of a cub with a red flower? You’ll leave Cathedral then, <PERSON>, when you’re on red, because they won’t let an adult stay here. The young ones. They’ll gut-rip you if you stay, so you’ll cross the river. And then, almost before you know it, <PERSON>, you’re twenty-one and your hand is blinking. And you’ll die like a sheep.”
Why is Cathedral filled with violent children? The novels and the movie differ on this.
In Logan’s World (1977), the second novel, Logan and <PERSON> encounter grown-up <PERSON> 2—the girl who gave them the key in Cathedral—who says she had been there because she was 5 years old and had “escaped from Nursery,” meaning she wouldn't have been raised in by machines. But in the 1976 movie script, <PERSON> suggests just the opposite, that the lack of natural mothering turned the cubs violent:
INT - MAZE-CAR - <PERSON> AND <PERSON> - MOVING SHOT
<PERSON> Have you ever been through Cathedral?
<PERSON> shakes her head.
<PERSON> They’re like beasts. Wild.
<PERSON> Maybe they’re angry because they're grown in meccano-breeders. 378