A topic I found interesting in The Sun Also Rises is the relationship between Jake and his masculinity -- specifically in the context of the gay men he comes across. With the "Iceberg Theory" in mind, I thought it was extremely illuminating how Hemingway shows both Jake's intolerance and the reason behind it. For Jake, masculinity seems to be a very sore subject, of course due to the injuries he has, and I noticed that it was heightened when he was mentioning the gay men. From what I gather from Jake as a character and the time period the novel is set it, I believe that Jake is essentially a homophobe because he finds homosexuality to be like a cruel mockery of his own situation. Jake's circumstances make him feel as though he is less masculine than a normal man and to him, homosexuality could look like men, who have all the "parts" required to be masculine, just throwing away that chance.
It would be interesting to see how the story changes (or would there even be a story?) if Jake didn't receive the same injuries he has now. Would he be more tolerant and less aggressive? Would he have more confidence in himself and allow love into his life? I guess it isn't really a fair thing to contemplate because so much of Jake's character is based on the scars but does raise some questions about the real world. I feel that everyone does things for a reason, whether they are aware of it or not, and we shouldn't be to quick to judge people.