How does The Witch Sketch Work Logically?

How does “The Witch Sketch” Work Logically?

 Given their deep academic backgrounds, the Pythons (aka Monty Python), a British comedy troupe of the 60s and 70s, featured many logical fallacies in their work.  (YouTube “the cheese shop sketch” or “the pet shop sketch” or “the argument clinic sketch” with the Python search modifier to see some of this.  One of my favorites is “Confuse a Cat”–and not just because it prefigures our fascination with silly cat videos!)

One of the most famous scenes from Monty Python and the Search for the Holy Grail is the witch sketch.  It delineates some logic for figuring out how someone is a witch.

Enjoy!  See if you can relate this to our problems of arguing definition.