T he Hatter is a fictional character in Lewis Carroll's Alice's Adventures in Wonderland and the story's sequel, Through the Looking-Glass. He is often referred to as the Mad Hatter, though this term was never used by Carroll. The phrase "mad as a hatter" pre-dates Carroll's works and the characters the Hatter and the March Hare are initially referred to as "both mad" by the Cheshire Cat, with both first appearing in Alice's Adventures in Wonderland, in the seventh chapter titled "A Mad Tea-Party". In the chapter "A Mad Tea Party", the Hatter asks a notable riddle: "Why is a raven like a writing desk?" When Alice gives up, the Hatter admits he does not have an answer himself. Lewis Carroll originally intended the riddle to be just a riddle without an answer, but after many requests from readers, he and others, including puzzle expert Sam Loyd, thought up possible answers to the riddle. In the preface to the 1896 edition, Carroll wrote:
Enquiries have been so often addressed to me, as to whether any answer to the Hatter’s Riddle can be imagined, that I may as well put on record here what seems to me to be a fairly appropriate answer,: "Because it can produce a few notes, though they are very flat; and it is never put with the wrong end in front!". This, however, is merely an afterthought; the Riddle as originally invented, had no answer at all".
A recent suggestion in terms of solution to the riddle is that "Poe wrote on both", referring to Edgar Allan Poe's famous poem 'The Raven' , presumably written on a writing desk.