One of the primary themes of the novel centers on the notion of a "separate peace." Lieutenant Frederic Henry, an American in the Italian Army, is severely wounded, recovers, returns to the war and, finally, after the powerfully rendered retreat from Caporetto, he deserts from the army in an effort to resolve and to escape the contradictions and chaos of a war-maddened world. In a kind of baptismal rite, he plunges into the Tagliamento River: "Anger was washed away in the river along with any obligation." His immersion in the river and flight from the war seal and signify his rebirth in love.

To be redeemed by love, of course, does not imply in Hemingway's tragic vision anything like a "happy ending." As Carlos Baker has succinctly stated the themes of this novel, Frederic and Catherine are "star-crossed," Catherine is "biologically double-crossed, Europe is war-crossed, and life is death-crossed." By the time Catherine dies in childbirth at the end of the novel, Frederic has not only been chastened by tragedy, but he has learned the meaning of commitment and love, and he is a better man for it.

The novel's intricately interwoven themes are perhaps distilled in this famous passage:

If people bring so much courage to this world the world has to kill them to break them, so of course it kills them. The world breaks everyone and afterward many are strong at the broken places. But those that will not break it kills. It kills the very good and the very gentle and the very brave impartially.

Another famous passage evokes yet another theme:

Abstract words such as glory, honor, courage, or hallow were obscene beside the concrete names of villages, the numbers of roads, the names of rivers.

These celebrated passages most certainly do not declare the meaninglessness of honor and courage in a world of nada, nothingness, or nihilism, as some have said, but they address the tragic condition and the problem of rhetoric, the burden of moral confusion that such abstractions have been made to bear. Neither passage leads to despair, but through the recognition of tragedy to the recovery of a lived, concrete sense of values. A final, somewhat neglected motif which underlines all of the major themes is suggested by Frederic's observation that "it is in defeat that we become Christian ... I don't mean technically Christian. I mean like Our Lord . . . We are all gentler now because we are beaten." Indeed, Hemingway's themes often have a strong Christian overtone, a specifically Catholic resonance, as one might expect of a Catholic convert.

Identity
In A Farewell to Arms, one of the themes of Frederic Henry’s adventure as an ambulance driver during World War I is identity. This theme compounds other themes that Hemingway is exploring through the war story. Identity is important to the story because it expresses the general question of the individual in the postwar world. The First World War raised some unsettling questions about the values the war generation had inherited. People began to question the validity of their national leaders and institutions which seemed to have led directly to such an incredible loss of life and economic devastation. Frederic represents, for Hemingway, this questioning of what is man that he can cause such awful destruction and human suffering.

Frederic’s identity is displaced by the late introduction of his name to the reader, the fact of his being an American in the Italian army, and his constant play with words. He speaks Italian, but not well enough to advance in rank. He also understands French and German but remains unmistakably American. None of this is surprising but because Hemingway depends on dialogue to a great extent, the play of words between languages serves to heighten such issues as alienation and patriotism. The former is heightened because jokes do not translate and thus Frederic’s efforts to lighten moods fall into silence. Beyond the curious problems of voice, Frederic always seems to be in the wrong outfit. This fact is exaggerated when he borrows clothes from Ralph Simmons to make his escape and when he says that his English gas mask works—whereas the Italian models do not. He continues to be someone else until the end. Finally, Frederic attempts to identify not as himself but as lost in Catherine—“We’re the same one.” He is forced to give this up when she dies.

Individualism
Hemingway’s novel demonstrates the demise of loyalty to traditions and institutions that had been brought forward from the nineteenth century, a refocusing on the self often referred to as “individualism.” His characters, especially Catherine Barkley (in terms of her fiance’s death at the hand of sophisticated infantry), all have war disgust. Each of them is able to avoid becoming crazy by falling back on the self. In doing so, each person rejects the “higher callings” of tradition, society, or institution. For example, Rinaldi has the satisfaction of having become a better surgeon through practice. He is also better with women for the same reason. When prodded by Frederic’s suggestion that there may be more than these two self-centered items in life, Rinaldi responds with a very existentialist statement, “We never get anything. We are born with all we have and we never learn. We never get anything new.”

It is out of this effort to come to terms with the stupidity and horror of the Great War that the school of thought known as existentialism emerges, a movement which suggested that men and women should not accept society’s or someone else’s values, but rather examine the truth in him or herself. Hemingway was not an existentialist, but his characters clearly exhibit a great deal of alienation from each other. They cope with their situation of doubt in society by developing an acute personal meaning. In A Farewell to Arms this is debated once by the priest and Frederic in the latter’s hospital room. Not for the first time, the reader is forced to examine the discomforting notions of love. The priest loves God and this comforts him during the war. Frederic and Catherine, alternately, display another route to coping. This one is ironic and looms large over the novel—“I want you so much I want to be you too.” This statement must be compared to their actions during the childbirth—Catherine is given hell by nature, while Frederic eats. The effort to be each other is an alienation from self and a failed method of coping. Thus, Frederic faces the tragedy of his love as well as the tragedy of himself—he did not listen to any of the tutors who warned him of this inevitability. Certainly, the inevitability is seen in hindsight since Catherine, as tradition and institution, died in the ghastly war leaving the “Everyman” tragically alone with himself.

Patriotism
The novel suggests that war has become a habit, a disgusting habit. At some point, Frederic has learned that this war is not romantic, and it most certainly does not concern him personally. He does not become a war-hardened soldier, but a disgusted ambulance driver who observes more facets of war than a soldier or politician would. Consequently, the notion of the patriot is reflected upon a few times, and the reader gains a definite sense that being a patriot is never to be equated to a love of war. However, that is not to say that Frederic ever clearly denounces or supports war because it is not in his character to be so passionate.

In the most obvious instance, Frederic returns to the front after his convalescence and chats about the war’s progress with one of his drivers, Gino. This driver declares himself a patriot and says he does not like to hear so many people talk of the Italians losing. Gino then launches into an invocation of patriotic language which Frederic cannot help but see as naive. It is at this point that Frederic admits his problem with words like “glorious,” “sacred,” and “sacrifice.” Frederic compares the notion of sacrifice to the stockyards of Chicago—one large slaughterhouse. Such a comparison, to the American reader at the time, was enough to question patriotism as a reason for war. If, Frederic asks, to love one's country is to be an animal slaughtered in the stockyards, then is it smart to be a patriot?

Doubt about the calling of every man to be a patriot is put to rest ambiguously when Count Greffi challenges Frederic to a game of pool. The wise old man tells Frederic that the slaughter does not define patriotism. Instead, a patriot is a lover of one’s countrymen. However, this is ambiguous precisely because there is little of this type of love on display during the retreat. All that Frederic saw in the retreat was the stupidity of war. The men who questioned his patriotism in retreat did not love him because he was an officer, and the battle police were present to kill him for his supposed betrayal. Unfortunately, one supposes, Count Greffi is no longer in charge and his vision of love is thus retired. The reader is left with an unanswered question: whether or not patriotism is an abstract value which is no longer possible to pursue rationally given the technical sophistication of death.

War
War is not glamorized in this novel. Instead, it is presented in a very real and horrifying fashion from the perspective of the ambulance driver. At some moments, war is derided as a game for the ruling classes in which the poor suffer. It is after this discussion, in Chapter IX, that the mortar hits. War is only rarely viewed in a patriotic light and more often seen as tiresome.

However, the negative portrayal of war in the novel may have as much to do with the almost futile effort of the Italian army. Frederic comments on this several times because he says he would be ashamed to be seen by the American, English, or French in such a “silly” army. Further ironies arise when his friends attempt to get him a medal for being wounded while eating macaroni.

Catherine tries to bolster the image of bravery at the end of Chapter XXI and even says that Frederic is brave. Frederic disagrees, saying that he is only a mediocre hitter. Thus war is a game, like baseball, and Frederic is not an outstanding player, but at best someone who can only do the most basic things.

War is also a disease. Rinaldi refers to his own condition of gonorrhea and says everyone has it. However, we know from earlier discussions that everyone too has war disgust. Therefore, Rinaldi's generalization equates war to a disease. That is, war is great, but like most things, after a time of too much indulgence, even pleasurable things become tiresome. The disease spreads and all one can do is have hope for a cure—the political end to the war. However, the cure simply allows a breathing space before the next burst of the disease.