For any of you who've ever suffered through a course on literary theory, Kate Hattemer's description thereof from The Vigilante Poets of Selwyn Academy:
(found on page 139)
".... [L]iterary theory is akin to the square root of negative one: we're just pretending it exists."
As someone who once pulled an A in a theory class by writing a 4700-word paper applying Judith Butler's take on the Hegelian dialectic tradition she claimed was in Sophocles' Antigone to the Fundamentalist LDS polygamous clans in Utah, I can assure you that Hattemer is spot-on in her description.
(PS If you are a normal person who has never attempted literary theory, don't even try to piece out my last sentence. Just don't.)