Lewis Carroll himself wrote the answer, after being badgered by people nonstop since the book's original publication. He said that, in the original book, there was no answer. To end the pain of ceaseless inquisitive fan letters, though, he went ahead and thought up an adequate response that he put in preface to later editions. Carroll's answer to why a raven is like a writing desk? "Because it can produce a few notes, tho they are very flat; and it is never put with the wrong end in front!"