Chapter 5 is one of the most important in the novel because it is here that we find the standard explanation of the meaning of "Catch-22." Yossarian is trying to understand why his friend Doc Daneeka won't ground anyone. Yossarian suggests his roommate Orr as an example:
"Is Orr crazy?"
"He sure is," Doc Daneeka said.
"Can you ground him?"
"I sure can. But first he has to ask me to. That's part of the rule."
"Then why doesn't he ask you to?"
"Because he's crazy," Doc Daneeka said. "He has to be crazy to keep flying combat missions after all the close calls he's had. Sure, I can ground Orr. But first he has to ask me to."
"That's all he has to do to be grounded?"
"That's all. Let him ask me."
"And then you can ground him?" Yossarian asked.
"No, then I can't ground him."
"You mean there's a catch?"
"Sure there's a catch," Doc Daneeka replied. "Catch-22. Anyone who wants to get out of combat duty isn't really crazy. . . ."
"That's some catch, that Catch-22," he [Yossarian] observed.
"It's the best there is," Doc Daneeka agreed.
"There was only one catch," the narrator tells us, "and that was Catch-22."
The novel later suggests other aspects of Catch-22, but this is its prime example: Orr can be grounded if he's crazy; but if he wants to be grounded, he must be sane. No matter where Yossarian or his friends turn, the military has them in its grip — and it all makes perfect sense.
