what is the central idea?

I think that the central theme of the story revolves around what it means to be human. Just as the Old Man is described in terms of his animal characteristics, so too he is described as human. Father Gonzaga thinks that he must be an imposter: he does not possess the dignity that people expect from angels. Also, in paragraph two the Old Man is described as a rag picker, and Pelayo and Elisenda decide that he must be a sailor. Despite these human characteristics, the Old Man is treated inhumanly. He is penned up with the chickens and displayed, forced to eat mush, and branded. This capacity to dehumanize a creature because of one unfamiliar characteristic - wings - quietly damns the people in the story. They see the Old Man's humanity yet don't feel the need to respond humanely.