In the poem, The Raven, Why does Poe choose a raven, supposedly a "non-reasoning creature"? What does it symbolize? Why was it so important to Poe that it could speak?

Poe seems to choose a raven, a "non-reasoning" creature, because it allows for ambiguity in the speaker's interpretation of the raven's speech. At first, the speaker assumes that the raven is only repeating the one word it knows: "Nevermore." He reasons that the bird likely had a somewhat melancholy owner who spoke the word often, inadvertently teaching it to the raven. However, he then begins to speculate that the bird is actually a gift from heaven, sent to distract him from his sorrow over his dead lover, Lenore. Still later, though, he begins to ascribe some nefarious purpose to the bird, conjecturing that the bird is actually an evil prophet come to terrify him by telling him that he will never again see Lenore, not even in death. We cannot know, for certain, which of these interpretations, if any of them, are correct. It is possible that the bird is non-reasoning, and it is also possible that the bird is there to torture the narrator. His speech matters because it is his speech that alerts the narrator to the bird's potentially supernatural origins.