What Is the Main Theme of "The Raven?"

Edgar Allen Poe's poem "The Raven" is driven by a theme of beauty, which Poe considered to be epitomized by sadness. The poem's sadness, then, derives from the story as it tells of a lost love, and a raven who brings back memories of this beloved woman. The narrator of the poem is lonely as a result of his loss, and finds company in a raven he fears will be gone by morning.