Joseph Heller's satirical novel, Catch-22, paints a picture of three kinds of soldiers: those who use the war for their own benefit, those who unquestioningly obey every order, and those who question their authorities and the purpose of war. The officers in this novel represent the first group; Clevinger and Yossarian represent the other two groups.
In chapter two of the novel, Yossarian and Clevinger have a heated argument about the war. It is Yossarian's belief that everyone with whom they are at war is trying to kill him; Clevinger insists that no one is trying to kill Yossarian specifically. Yossarian's logic runs Clevinger in circles until finally Clevinger just asserts angrily that Yossarian is crazy. (Of course, Yossarian wishes this were a true diagnosis so he would be discharged, but the doctor is not impressed with Clevinger's claim of Yossarian's mental state.)
This is an ongoing point of contention between the men until Clevinger eventually disappears during a battle. Later in the novel, Yossarian reaches the startling conclusion that Clevinger had a change of heart and deserted.