Moving the Goalposts

In plain terms

Someone asks for evidence. You provide it. Instead of accepting it, they raise the bar: now they want different evidence, more evidence, better evidence. Provide that too, and the bar moves again. The goal was never a standard you could meet. The goal was to keep you running.

The name comes from sport. Imagine kicking the ball between the posts, only for someone to pick the posts up and walk them further down the field, then insist you never really scored.

Why it's fallacious

An honest demand for evidence comes with an implicit promise: if the evidence arrives, the claim is accepted. Moving the goalposts breaks that promise. The new, higher standard is introduced precisely because the old one was met, which means no standard was ever going to be enough.

This makes the argument unfalsifiable from the other direction. There is no outcome that counts as you being right, because the finish line relocates every time you approach it.

Canonical example

A: "There's no evidence this policy reduced emissions."

B: "Here's the state's monitoring data showing a 12% drop."

A: "Sure, but that's just one state. Show me it works nationwide."

B: "Here's the federal aggregate, also down."

A: "Correlation isn't causation. Show me a controlled experiment."

Each time B meets the standard, A raises it. The first demand was "any evidence." By the third, it's "a controlled experiment," a bar A never mentioned and may have known was impractical. The discussion looks like rigor. It functions as evasion.

Counter-example (not a fallacy)

A: "This drug is safe; the phase II trial showed no serious side effects."

B: "Phase II is a small sample. Safety claims for public release usually need phase III data. That's the standard, not a new hurdle I invented."

This isn't moving the goalposts. B is pointing to a pre-existing, well-defined standard that A's evidence genuinely doesn't meet. The bar didn't move; A just hadn't cleared it yet. Asking for the appropriate level of evidence is legitimate. Inventing a higher level after the appropriate one is met is the fallacy.

The line: was the new standard always the real standard, or did it appear only because the old one was satisfied?

How to fix it

If you've been linked here, the fix is to state your evidence standard up front and hold to it. Before the other side responds, decide what would actually change your mind: "If you can show me X, I'll accept the claim." Then, when they show you X, accept it, or explain why X turned out not to be the right standard and own that you're revising. What you can't do, in good faith, is treat every satisfied demand as a reason to invent a new one.

If you're on the receiving end, pin the standard down early. "What specifically would convince you? If I show you that, will you accept the claim?" Get the answer before you do the work. If the bar moves afterward, you can point back to what was agreed.