u/iMoosker

I've been trying to wrap my head around this Motte-and-bailey fallacy Wikipedia article (let's call it M&B for short). Then I ran into an interesting edge case in which a two contradicting propositions could be a Motte-and-bailey doctrine but it would not be a fallacy. That's when I discovered an interesting distinction that is often overlooked, perhaps by fault by its creator Nicholas Shackel.

Motte-and-bailey doctrine was coined by Philosopher Nicholas Shackel in 2005 in his paper. Shackle explains that the M&B doctrine is simply the pair of different propositions (the hard-to-defend Bailey, the defensible Motte).

What happened is people concluded that, hey! If someone deploys the motte and bailey together to create their argument, it can lead to a fallacy. Basically, If Bailey is true -> then Motte is true

“It is possible that I am partly to blame for that misunderstanding”
“Some people have spoken of a Motte and Bailey Doctrine as being a fallacy and others of it being a matter of strategic equivocation. Strictly speaking, neither is correct. A fallacy is an argument that is invalid and equivocation is giving different meanings to the same terms when you should be keeping their meaning invariant. A doctrine, however,  is a body of propositions, not an argument. So a Motte and Bailey Doctrine cannot be a fallacy and shifting from asserting the Bailey propositions to the Motte propositions is not in general effected by giving different meanings to the same words or statements.”
"So it is, perhaps, noting the common deployment of such rhetorical trickeries that has led many people using the concept to speak of it in terms of a Motte and Bailey fallacy."

Now let's look at a complex example.

• Person A: "All X are Y."
• Critic: "I've seen some X that are not Y."
• Person A: "Duh. Not all X are Y."
• Person A: "I'm not going to tell Critic that I still think all X are Y right now."

Is this example an M&B Doctrine?

Yes. But how? It's because the doctrine only requires two related propositions: a desirable but difficult-to-defend (B) and an easier-to-defend (M).

Is there a fallacy here?

No. There isn't an argument here, therefore there is no fallacy.

If we pushed it to turn it into an argument, such as: “Not all X are Y, therefore all X are Y”, then it could technically be a fallacy since it is an argument built on faulty reasoning.

A better example for you.

Here’s an example I developed that would be an M&B Doctrine that is used to turn into an argument and therefore a fallacy.

• Me: AI is a human being (Motte)
• Critic: That's false. AI isn't biologically human.
• Me: All I’m saying is AI can pass the Turing Test (Bailey)
• Critic: I agree with that.
• Me: You admitted that AI can pass the Turing Test. And if it can pass the Turing Test, that means it is a human (Fallacy)

Scott Alexander, 2014, in the Slate Star Codex:
“One of the better things I’ve done with this blog was help popularize Nicholas Shackel’s “motte and bailey doctrine”. But I’ve recently been reminded I didn’t do a very good job of it.”