Washington Irving is having fun with his audience by telling his audience that the story of Rip Van Winkle by creating several layers of doubt as to the “unquestionable authority” of the story.
Even though the only one who could know what happened on the mountain is Rip himself, he is not the narrator. Knickerbocker says he heard the story from Rip himself, and he though he believes it, he is not the narrator. Since the story comes from the The Sketch Book of Geoffrey Crayon, Gent., the narrator of “Rip Van Winkle” is Geoffrey Crayon, even though Crayon says he got the story from papers left behind by Knickerbocker.
Washington Irving had a genius for inventing comic fictional narrators. In fact, he did not sign his real name to his work until he was over fifty. He had two narrators, Jonathan Oldstyle, Gent., a caricature of the British writers who could not accept the simple values of the new nation, and Diedrich Knickerbocker, a Dutchman. He it is who leaves the tale of Rip van Winkle, and the story is framed by an unknown writer.
The following tale was found among the papers of the late Diedrich Knickerbocker; an old gentleman of New York, who was very curious in the Dutch history of the province, and the manners of the descendants from its primitive settlers.
Because Knickerbocker was known for his "scrupulous accuracy," the unknown writer states, the tale of Rip van Winkle should be taken as entirely accurate.
The plot of Washington Irving's "Rip Van Winkle" is framed before and after by material that does not advance the plot. The purpose of the material which frames the plot is to create the illusion that the story is fact and not fiction.
Washington Iriving with tongue in cheek irony attests in the opening section of the frame by means of the quotation in verse:
By Woden, God of Saxons,
From whence comes Wensday, that is Wodensday,
Truth is a thing that ever I will keep
Unto thylke day in which I creep into
My sepulchre CARTWRIGHT.
and a note explaining where the story came from to the veracity of the story.Irving reiterates the claims to the truth of the story after the story has been narrated, by means of the narrator attesting to the truth of the story and by quoting from the letter of Knickerbocker stating that the story is true "beyond the possibility of doubt."
The only one who knows what Rip saw on that mountain is Rip himself. He has told the story frequently, but he is not the narrator of Rip Van Winkle. In the note at the end of the story, Knickerbocker claims to have heard the story from Rip's own mouth and Knickerbocker gives it his full belief. But it is not Knickerbocker, either, who tells the story, but a different narrator. Readers of the entire The Sketch Book of Geoffrey Crayon, Gent. know that the narrator is Geoffrey Crayon, Gent. (for gentleman), the purported author of the book. Crayon claims to have found the manuscript of Rip Van Winkle among papers left behind by Knickerbocker after his death, and Crayon appears to revere Knickerbocker for his unquestionable authority.
The frame creates, then, several layers of doubt. Crayon, of questionable judgment, has the story from the unreliable Knickerbocker (if he is telling the truth about the manuscript), who has it from Rip, who in the beginning used to vary on some points every time he told it.
So, it is impossible to identify and deconstruct the exact identity of the narrator of "Rip Van Winkle." The irony being that everytime Irving insists on the truth of the story he is actually denying it.
The narrator of "Rip Van Winkle" was Diedrich Knickerbocker. It's actually Washington Irving pen name.