postoak... There is no question that Hemingway thought of himself as a great writer, perhaps "the greatest" writer of his generation. He was to 20th century fiction writing what Muhammed Ali was to boxing in his prime, and he knew it.
I have to disagree that Hemingway's content was all that revolutionary... if you read his contemporaries, Joyce and Fitzgerald, they're equally frank about sex and conflict and drinking. His style and disciplined writing technique was what set him apart, and he drew that from both his journalist background as well as his tutelage by Gertrude Stein.
As for his understanding of the "underlying issues" in The Sun Also Rises, EH was very much aware of what he was writing about. Reading his letters and his biographers makes that abundantly clear.
As Richard Austin points out, EH's style was much more poetical than most prose writers of his--or most any other--day, in that he said almost as much by what he didn't write as by what he did write.
