"I know what you're thinking about," said Tweedledum; "but it isn't so, nohow." "Contrariwise," continued Tweedledee, "if it was so, it might be; and if it were so, it would be; but as it isn't, it ain't. That's logic."

The Complete Works of Lewis Carroll, Through the Looking-Glass, Chapter IV (p. 181), The Modern Library. 1936