A storyteller who made up an account about Jesus in order to prove a point may well have known that he was passing off a fiction as a historical event. A scribe who wanted a text to say something other than what it did may well have changed the text for just that reason. In some cases it is hard to imagine how else the resultant deception could have come about. Whoever added the final twelve verses of Mark did not do so by a mere slip of the pen.