Moby Dick is considered to be one of the Great American Novels and a treasure of world literature. The story tells the adventures of wandering sailor Ishmael, and his voyage on the whaleship Pequod, commanded by Captain Ahab. Ishmael soon learns that Ahab has one purpose on this voyage: to seek out a specific whale-Moby Dick, a ferocious, enigmatic white sperm whale. In a previous encounter, the whale destroyed Ahab's boat and bit off his leg, which now drives Ahab to take revenge. In Moby Dick, Melville employs stylized language, symbolism, and metaphor to explore numerous complex themes. Through the main character's journey, the concepts of class and social status, good and evil, and the existence of God are all examined, as Ishmael speculates upon his personal beliefs and his place in the universe.