Doubt versus ambiguity is one of the major themes in this story. The reader is not given any clear cut answers in this story. Many issues do not get resolved, and the reader is left to wonder about the old man with wings. Is he an angel, some unknown species, or merely a mortal with wings? The author does not give the reader the answer, it is up to the reader to draw their own conclusions.
The ambiguity of the tale-the loose ends- are what make the story fantastic. It gives it a real feel. Rarely in life are people given resolution to their own events neatly tied up and concluded. This is true for the story, as well.
The elements of fantasy are what make the story, and the confusion of real versus fantasy is the purpose. The questions and unresolved issues are left for the reader to "make sense" of themselves. We must decide what happened and what is "real".