Yossarian is quite impressed by the simple logic of it all and emits a respectful whistle. "That's some catch, that Catch-22," he observes. Doc Daneeka responds, "It's the best there is."
As a theme, the catch is that anyone under military or political authority has to submit to the will of authority. When Yossarian goes to Rome near the end of the novel and speaks with an old woman, the only one left in the brothel, she tells him that military police and the carabinieri ran the girls out of the apartment building under the authority of Catch-22. Although no one ever actually sees Catch-22, the entire military complex functions under its authority. Why does everyone submit? Because Catch-22 is the law. Who says so? Catch-22, of course.
When Colonel Korn and Colonel Cathcart call Yossarian into their office to discuss the arrangement for his release from military duty (Chapter 40), Yossarian briefly seems to have the commanding officers in a Catch-22. On the one hand, they cannot simply send him home if it looks like a reward for refusing to fly more missions. That would destroy morale. On the other hand, Korn and Cathcart would put their own careers in jeopardy if Yossarian remains with the squadron, refuses to fly, and has other men following his example. In time, of course, Catch-22 prevails on the side of the establishment. Yossarian must either accept the odious deal that he is offered, or he will be court-martialed. It's some catch, that Catch-22.
