Motte-and-bailey fallacy

The motte-and-bailey fallacy is a way of arguing where someone uses two different ideas that seem similar but are not the same. One idea (the "motte") is easy to defend and not very controversial. The other (the "bailey") is more controversial and harder to defend. When someone argues for the controversial idea but gets challenged, they switch to defending the less controversial one. This makes it look like their original point is still valid, even though they are now arguing something different.

History and Name

This fallacy (incorrect argument in logic and rhetoric) is named after a type of medieval castle called a motte-and-bailey. Nicholas Shackel, a philosopher, first talked about this fallacy in 2005. He compared it to the castle's defense strategy. In a motte-and-bailey castle, there's a stone tower on a hill (the motte) and a land area around it (the bailey). If attackers come, people in the castle retreat to the motte, which is easier to defend. Similarly, in the fallacy, the arguer retreats to the easier-to-defend idea when their main idea is attacked.