Cohn has spent his entire life feeling like an outsider because he is Jewish. While at Princeton, he took up boxing to combat his feelings of shyness and inferiority. Although his confidence has grown with his literary success, his anxiety about being different or considered not good enough persists. These feelings of otherness and inadequacy may explain his irrational attachment to Brett—he is so terrified of rejection that, when it happens, he refuses to accept it.
The individuals with whom Cohn travels to Spain only compound his insecurities. Not only is he the only Jew among them, but he is also the only nonveteran. Jake and his friends seize on these differences and take out their own personal insecurities on Cohn. It is important to note that Cohn’s behavior toward Brett is ultimately not very different from that of most of the men in the novel. They all want to possess her in ways that she resists. But Cohn’s attempts to win Brett are so clumsy and foolish that they provide an easy target for mockery.
Cohn adheres to an outdated, prewar value system of honor and romance. He fights only within the confines of the gym until his rage and frustration make him lash out at Romero and Jake. He plays hard at tennis, but if he loses he accepts defeat gracefully. Furthermore, he cannot believe that his affair with Brett has no emotional value. Hence, he acts as a foil for Jake and the other veterans in the novel; unlike them, he holds onto traditional values and beliefs, likely because he never experienced World War I firsthand.
Sadly, Cohn’s value system has no place in the postwar world, and Cohn cannot sustain it. His tearful request that Romero shake his hand after Cohn has beaten him up is an absurd attempt to restore the validity of an antiquated code of conduct. His flight from Pamplona is symbolic of the failure of traditional values in the postwar world.