Motte-and-Bailey Fallacy
Motte and Bailey Doctrine
The fallacy where an arguer conflates two similar positions — one modest and easy to defend (the "motte") and one much more controversial (the "bailey"). The arguer advances the controversial position, but when challenged, they insist that they are only advancing the more modest position.
Origin
Philosopher Nicholas Shackel coined the term in his 2005 paper "The Vacuity of Postmodernist Methodology" in Metaphilosophy. He borrowed the metaphor from the motte-and-bailey castle — a medieval fortification with an easily held stone tower (the motte) surrounded by a desirable but hard-to-defend courtyard (the bailey). Shackel's original target was postmodernist academics, but the concept was widely popularized by the blog Slate Star Codex in 2014.
Everyday Use
Someone makes a bold claim in a meeting. When pushed back, they retreat to a much milder version: "I was just saying we should consider it." Once the pressure's off, the bold claim creeps back. You see this in political rhetoric, marketing, and everyday arguments — shuttle between the safe version and the ambitious one as needed.