I'm sorry, this is a short-answer forum, we are unable to assist students with essays, but I can give you afew ideas. Cohn is the only main character in the novel, who has not been to war. Because of this, he's different..... definitely an outsider, as he cannot relate to the other male characters' experiences. Cohn is an idealist..... a romantic, something that separates him from the other characters because the experience of war has robbed them of whatever idealism they possessed. On the whole, Cohn isn't well liked.
Jake, on the other hand, is well liked by everyone and cares for no one. He lacks responsibilty, and lives it up..... drinking and carousing, because he can never love the woman he wants in the way he feels she needs to be loved. Like Cohn, Jake often feels inferior, but this is a result of his injuries in war.... injuries that have left him impotent. Where Cohn still has the ability to be hopeful, Jake lives in a world where he believes his own life to be hopeless.