The plot structure of Catch-22 is unusual in several respects, requiring careful attention from the reader. The timeline is quite disorienting, and much of it entails reminiscences of the various characters. Figures that are alluded to by other characters are often not more fully developed and explored until the chapter that focuses on them. Hence, much of the description and anecdotes seem quite incidental. Although the pieces contribute to a more complete picture of the character, the reader who wants a full understanding of each character’s story must sift through the material. Furthermore, to find the main plot, more sifting for relevance is necessary. Despite this confusion, Heller maintains the reader's interest by using a great deal of foreshadowing and memory. Seemingly arbitrary episodes and flashbacks, such as Yossarian's traumatic recollections of Snowden's death, are common devices throughout. The importance of the flashback of Snowden's death cannot be understated; for Yossarian the experience is a touchstone.
The content of the plot touches on several crucial themes that form the groundwork for the maddening atmosphere of Pianosa. First, Yossarian constantly reiterates his right to life and using whatever means he can to save himself from being killed. Survival, not winning the war, is what matters to him. Meanwhile, he questions the morals of the country that has made him serve and fly too many missions. Captain Black's episode with the Glorious Loyalty Crusade points out how patriotism can be abused for someone's personal ambition or agenda. Religion is also repeatedly questioned; the chaplain himself is thrown out of the officers' headquarters and happily lives in his own world. Even the chaplain has his doubts about God and morality, and once when he lies, he feels wonderful about it. The institutions that run and support the war, the military establishment, the government, business, and the medical institution are also severely satirized. These larger contexts help us fit the details together.
Perhaps the most targeted institution is the military establishment. Throughout the book, it is criticized for its bureaucracy, its inner squabbling, the absurd tactics to move up the ranks, and its absurd obsessions. Generals Peckem and Dreedle continuously squabble Colonel Cathcart constantly increases the number of missions in an attempt to be promoted to general. Business, represented by Milo, becomes a parasite that profits from the war. This financial obsession is so bad that even Milo is willing to destroy his own squadron simply to ensure a profit. Finally, throughout the novel, the doctors in the medical institution are presented as ignorant and presumptuous, treating their patients without compassion, and sometimes even with inhumanity. This is a particularly sad reversal on the traditional mission of doctors to heal, preserve life, and do no harm. The representative character in this regard is Doc Daneeka. He never listens to anyone's troubles and refuses to ground any of the men. These plot contours, too, help us fit the pieces of the plot together.
Last, and perhaps most important, the viewpoint and logic of the “Catch-22” exposes the dangers of the war. Daneeka points out that the men are trapped because those who are mad will fly the missions and if they deny madness, they will be forced to fly them because they are capable of doing so. Orr turns this logic against the military bureaucracy when he begins to hope for the improbable: that he can row to Switzerland in a boat, using an oar the size of a Dixie-cup spoon. After all, which is more likely: that he will get to Switzerland before the war ends, or that Colonel Cathcart will allow the men to take leave and return home? The Catch-22 is a way of looking at the world reflected again and again in the plot of the novel. In rationalizing absurd ends, common sense tends to be jettisoned. Minor incidents such as the falsified theft of a plum tomato become the crucial points of evidence against the chaplain. Calamities such as the death of Nately are blown off as unimportant because they do not serve as useful evidence in achieving the military's ends. This lack of perspective and this disproportion only underscore the horrifying lessons of the war: that rationalization rather than reason tends to dictate actions. This point should be kept in mind as the reader assembles the plot of the novel.