One linguist says, "Words mean whatever people think they mean."
The other linguist says, "No, words mean what a contemporary dictionary says they mean. There is such a thing as the correct meaning of a word."
The first linguist says, "No, how ordinary people use a word must be the real test of correctness."
The second linguist says, "Okay. Let's find the most ordinary person we can find and ask him to define a word." So they find the guy who is in the Guinness Book of World Records as "world's most ordinary person."
The second linguist asks the ordinary man, "Define "dictionary.""
The ordinary man says, "A book that tells you the correct spelling and definition of words."
An observation from one of Pinker's books, dressed up here as a very dry joke.