Ok, let's take an obscure subject of debate and slam it head first into the hulking abomination called Spam dominating this forum, shall we ?
Some people would support the argument that a Jack is a Jack. Others would support the argument that a Jack is not a Jack but a Knave. Logically then we can conclude that Jacks are not Knaves and Knaves are not jacks.
So, what do you call them ?