The narrator is an observant young man from Manhattan, perhaps even as young as Melville was (twenty-one) when he first sailed as a crew member on the American whaler Acushnet. Ishmael tells us that he often seeks a sea voyage when he gets to feeling glum. Four times he has sailed in the merchant service (so he may well be in his mid-twenties or older). This time he has a yearning for a voyage on a whaling ship. Thus we have a story — because of Ishmael's desire for a whaling venture, his keen observation, his ability to spin a yarn, his ability to grow and learn, and his unique survival. If Ishmael doesn't live, we have no story.
Ishmael probably is a more interesting narrator because he is a loner by nature. This allows him further objectivity and a freedom of evaluation that more involvement might dissuade. Melville frequently employs biblical allusions as keys to understanding in the novel, and he does so here. The biblical Ishmael (Genesis 16:1-16; 21:10 ff.) is disinherited and dismissed from his home in favor of his half-brother Isaac. The name suggests that the narrator is something of an outcast, a drifter, a fellow of no particular family other than mankind. Ishmael confirms his independent ways by telling us that he seeks no special rank aboard ship and would not want to be either a cook or a captain; he says he has enough responsibility just taking care of himself. Ishmael speaks of no family or even a last name. This is consistent with the ending of the book in which only Ishmael survives, picked up by the whaling ship Rachel, which, searching after its own missing children, finds only "another orphan" (Epilogue).
Ishmael's isolation makes his one real friendship, with the Polynesian harpooner Queequeg, all the more important. Part of Ishmael's appeal as a narrator is that he is an open-minded character who is capable of change and growth. When he first meets Queequeg, in a bed they share at the Spouter-Inn, Ishmael is terrified. He sees the South Seas islander as a stereotypical "heathen" and fears that he is about to be killed by a cannibal. Just the opposite is true. Ishmael soon learns that Queequeg is one of the finest men he has ever known — caring, kind, generous, loyal, courageous, and wise. Together, they explore the rich possibilities existing in diversity. Ultimately, it is this acceptance that indirectly saves Ishmael's life.