The peasants in this video believe the woman is a witch. Why? “She looks like one.”
This, however, is not good enough for the knight, Sir Bedevere, a man of science. He proposes a simple way to determine her guilt.
What do the people do with witches? Burn them.
And what burns, other than witches? Wood.
Well then, why do witches burn? Because they’re made of wood.
How do we find out, then, if she is made of wood?
Does wood sink in water? No, it floats.
What else floats in water? A duck.
If she weighs the same as a duck, she’s made of wood.
And if she’s made of wood, she is therefore a witch.
1. All witches are things that can burn.
2. All things that can burn are made of wood.
3. Therefore, all witches are made of wood. (1 & 2)
4. All things that are made of wood are things that can float.
5. All things that weigh as much as a duck are things that can float.
6. So all things that weigh as much as a duck are things that are made of wood. (4 & 5)
7. Therefore, all witches are things that weigh as much as a duck. (3 & 6)
8. This thing is a thing that weighs as much as a duck.
9. Therefore, this thing is a witch. (7 & 8)
There are many ways that these premises are invalid and this argument unsound, which have been further deconstructed here. But even at a glance, we know that not everything that burns is made of wood, weighing the same as a duck does not guarantee flotation, etc.
In the Monty Python world, this kind of logic exists often. It helps to introduce the type of humour used in Python as well as how ridiculous they can be. I find Monty Python’s use of humour to be quite entertaining and effective.