hmm...that's a good question. I've always thought that Poe didn't give the narrator a name because he wanted him to represent rationality. Without a name, and with very little biogrphical detail given (all we really know about the narrator is that he was a childhood friend of Roderick) we can assume that the narrator is objective. However, you could just as equally argue that since we don't know anything about the narrator, that he in fact isn't rational, and that what he sees/tells the reader isn't reliable. Some have suggested in fact, that the ending is just a figment of the imagination of an unreliable narrator. I believe the former, however, because there is nothing in the writing to lead one to believe that the narrator is anything but objective and reliable.