There are several main themes running through Heller's book. A major one is of the nature of sanity. Yossarian is essentially one of the few sane people in an insane situation. Most of the other characters react to the situation by becoming equally crazy. The question then is whether Yossarian is even more insane, by trying to be sane. The other themes all seem to come back to this main one in one manner or another. Heller deals with the role of individuals in society, and what it means to be a hero. But because these are played out against such an insane setting, they are necessarily slanted in toward the main question of sanity vs. insanity. For examples of all of these, see the below link.
In addition to the theme of sanity in insane world, two of the other main themes of Joseph Heller's Catch-22 are its obvious anti-war messages and its view of heroes and heroism. The aburdity of the various catches--particularly when the number of missions required to be sent home is raised constantly so that few men can accomplish the goal--is one of Heller's favorite themes. Cowards become heroes (Aarfy, Milo Minderbinder) and heroes are labeled as cowards (Yossarian). Probably the best examples of Heller's anti-war stance come when Orr finally succeeds in bailing out and sailing away; and when Yossarian discovers Orr's success and decides to try to duplicate the feat.
Also one of my favorite novels, and i believe one of the most significant novels of our time. One of the first themes developed in the novel is the question of what is right to do in a basic moral dilemma/social dilemma; where a person can cooperate with others to their collective greater payoff; or can sell them out by not cooperating, and reap even greater benefits as an individual. Yossarian is presented as having decided upon and relishing the immoral choice to such questions. Yossarian (and Doc Daneeka) often wonder "why me" when it comes to taking risks when others aren't. To this, Major Danby asks Yossarian, "But suppose everybody on our side felt that way", to which Yossarian replies, "Then I'd certainly be a damned fool to feel any other way. Wouldn't I?"
Another theme is the turning on their heads of notions of what people generally think of as morally right or wrong, particularly patriotism and honor, which lead most of the Airmen to accept abusive lies and petty rules of bureaucrats, though Yossarian whole-heartedly disregards all such notions. When Major Major asks why he wouldn't fly more missions, Yossarian answers:
"That's nothing to be ashamed of," Major Major counseled him kindly. "We're all afraid."
"I'm not ashamed," Yossarian said. "I'm just afraid."
Several themes flow into one another, for example, "that the only way to survive such an insane system is to be insane oneself", is partially a take on Yossarian's answer to the Social dilemma (that he would be a fool to be any other way); and another theme, "that bad men (who sell out others) are more likely to get ahead, rise in rank, and make money", turns our notions of what is estimable on their heads as well.
As the novel progresses, Yossarian comes to fear American bureaucrats more than he fears the Germans attempting to shoot down his bomber; he feels that a majority of people are "out to get him", regardless of their nominal allegiance. Among the reasons Yossarian fears his commanders more than the enemy is that, as he flies more missions, the number of missions required before he can go home is continually increasing: he is always approaching the magic number, but he never reaches it. He comes to despair of ever getting home and is greatly relieved when he is sent to the hospital for a condition that is almost jaundice. In Yossarian's words: "The enemy is anybody who's going to get you killed, no matter which side he's on, and that includes Colonel Cathcart. And don't you forget that, because the longer you remember it, the longer you might live." (Chapter 12)
heres a list of the remaining Themes/Motifs:
- Sanity and insanity
- Heroes and heroism
- Absurdity and inefficiency of bureaucracy
- Power of bureaucracy
- Questioning/Loss of religious faith
- Impotence of language
- Inevitability of death
- Distortion of justice
- Concept of Catch-22
- Personal integrity
- Capital and its amorality
from my own annalysis of the novel plus a little help from a friend (not wiki--->), yes i know wicki isnt the best source but follow the links at the bottom.